Add a driver for AMD AGESA ALIB Function 0x0C, the Dynamic Power and
Thermal Configuration interface (DPTCi). This exposes TDP and thermal
parameters for AMD APU-based handheld devices via the
firmware-attributes sysfs ABI.

Parameters are staged and atomically committed through ALIB. The driver
supports two save modes: "single" (apply immediately on write) and
"bulk" (stage values, then commit with "save"). An "expanded_limits"
toggle widens the allowed parameter ranges beyond device defaults.

Initial device support: GPD Win 5 (AMD Ryzen AI MAX).

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
---
 MAINTAINERS                       |   6 +
 drivers/platform/x86/amd/Kconfig  |  14 +
 drivers/platform/x86/amd/Makefile |   2 +
 drivers/platform/x86/amd/dptc.c   | 747 ++++++++++++++++++++++++++++++
 4 files changed, 769 insertions(+)
 create mode 100644 drivers/platform/x86/amd/dptc.c

diff --git a/MAINTAINERS b/MAINTAINERS
index e08767323763..915293594641 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1096,6 +1096,12 @@ S:	Supported
 F:	drivers/gpu/drm/amd/display/dc/dml/
 F:	drivers/gpu/drm/amd/display/dc/dml2_0/
 
+AMD DPTC DRIVER
+M:	Antheas Kapenekakis <lkml@antheas.dev>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/amd/dptc.c
+
 AMD FAM15H PROCESSOR POWER MONITORING DRIVER
 M:	Huang Rui <ray.huang@amd.com>
 L:	linux-hwmon@vger.kernel.org
diff --git a/drivers/platform/x86/amd/Kconfig b/drivers/platform/x86/amd/Kconfig
index b813f9265368..d610092467fc 100644
--- a/drivers/platform/x86/amd/Kconfig
+++ b/drivers/platform/x86/amd/Kconfig
@@ -44,3 +44,17 @@ config AMD_ISP_PLATFORM
 
 	  This driver can also be built as a module. If so, the module
 	  will be called amd_isp4.
+
+config AMD_DPTC
+	tristate "AMD Dynamic Power and Thermal Configuration Interface (DPTCi)"
+	depends on X86_64 && ACPI && DMI
+	select FIRMWARE_ATTRIBUTES_CLASS
+	help
+	  Driver for AMD AGESA ALIB Function 0x0C, the Dynamic Power and
+	  Thermal Configuration Interface (DPTCi). Exposes TDP and thermal
+	  parameters for AMD APU-based handheld devices via the
+	  firmware-attributes sysfs ABI, allowing userspace tools to stage
+	  and atomically commit power limit settings. Requires a DMI match
+	  for the device and a recognized AMD SoC.
+
+	  If built as a module, the module will be called amd_dptc.
diff --git a/drivers/platform/x86/amd/Makefile b/drivers/platform/x86/amd/Makefile
index f6ff0c837f34..862a609bfe38 100644
--- a/drivers/platform/x86/amd/Makefile
+++ b/drivers/platform/x86/amd/Makefile
@@ -12,3 +12,5 @@ obj-$(CONFIG_AMD_PMF)		+= pmf/
 obj-$(CONFIG_AMD_WBRF)		+= wbrf.o
 obj-$(CONFIG_AMD_ISP_PLATFORM)	+= amd_isp4.o
 obj-$(CONFIG_AMD_HFI)		+= hfi/
+obj-$(CONFIG_AMD_DPTC)		+= amd_dptc.o
+amd_dptc-y			:= dptc.o
diff --git a/drivers/platform/x86/amd/dptc.c b/drivers/platform/x86/amd/dptc.c
new file mode 100644
index 000000000000..acfe9cc01bab
--- /dev/null
+++ b/drivers/platform/x86/amd/dptc.c
@@ -0,0 +1,747 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD Dynamic Power and Thermal Configuration Interface (DPTCi) driver
+ *
+ * Exposes AMD APU power and thermal parameters via the firmware-attributes
+ * sysfs ABI. Parameters are staged and atomically committed through the
+ * AGESA ALIB Function 0x0C (Dynamic Power and Thermal Configuration
+ * interface).
+ *
+ * Reference: AMD AGESA Publication #44065, Appendix E.5
+ *            https://docs.amd.com/v/u/en-US/44065_Arch2008
+ *
+ * Copyright (C) 2026 Antheas Kapenekakis <lkml@antheas.dev>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/cleanup.h>
+#include <linux/dmi.h>
+#include <linux/init.h>
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/processor.h>
+#include <linux/sysfs.h>
+#include <linux/unaligned.h>
+
+#include "../firmware_attributes_class.h"
+
+#define DRIVER_NAME		"amd-dptc"
+
+#define ALIB_FUNC_DPTC		0x0C
+#define ALIB_PATH		"\\_SB.ALIB"
+
+#define ALIB_ID_TEMP_TARGET	0x03
+#define ALIB_ID_STAPM_LIMIT	0x05
+#define ALIB_ID_FAST_LIMIT	0x06
+#define ALIB_ID_SLOW_LIMIT	0x07
+#define ALIB_ID_SKIN_LIMIT	0x2E
+
+enum dptc_param_idx {
+	DPTC_PPT_PL1_SPL,	/* STAPM + skin limit (set together) */
+	DPTC_PPT_PL2_SPPT,	/* slow PPT limit */
+	DPTC_PPT_PL3_FPPT,	/* fast PPT limit */
+	DPTC_CPU_TEMP,		/* thermal control target */
+	DPTC_NUM_PARAMS,
+};
+
+struct dptc_param_limits {
+	u32 expanded_min;
+	u32 device_min;
+	u32 def;
+	u32 device_max;
+	u32 expanded_max;
+};
+
+struct dptc_device_limits {
+	struct dptc_param_limits params[DPTC_NUM_PARAMS];
+};
+
+struct dptc_param_desc {
+	const char *name;
+	const char *display_name;
+	u16 scale;	/* sysfs-to-ALIB multiplier (e.g. 1000 for W->mW) */
+	u8 param_id;
+	u8 param_id2;	/* secondary ALIB ID, 0 if none */
+};
+
+static const struct dptc_param_desc dptc_params[DPTC_NUM_PARAMS] = {
+	[DPTC_PPT_PL1_SPL]  = { "ppt_pl1_spl",  "Sustained power limit (W)",
+		1000, ALIB_ID_STAPM_LIMIT, ALIB_ID_SKIN_LIMIT },
+	[DPTC_PPT_PL2_SPPT] = { "ppt_pl2_sppt", "Slow PPT limit (W)",
+		1000, ALIB_ID_SLOW_LIMIT },
+	[DPTC_PPT_PL3_FPPT] = { "ppt_pl3_fppt", "Fast PPT limit (W)",
+		1000, ALIB_ID_FAST_LIMIT },
+	[DPTC_CPU_TEMP]     = { "cpu_temp",     "Thermal control limit (C)",
+		   1, ALIB_ID_TEMP_TARGET },
+};
+
+/* AI MAX Handheld class: GPD Win 5 */
+static const struct dptc_device_limits limits_maxhh = { .params = {
+	[DPTC_PPT_PL1_SPL]  = {  0,  4, 25,  80, 100 },
+	[DPTC_PPT_PL2_SPPT] = {  0,  4, 27,  82, 100 },
+	[DPTC_PPT_PL3_FPPT] = {  0,  4, 40,  85, 100 },
+	[DPTC_CPU_TEMP]     = { 60, 70, 95,  95, 100 },
+}};
+
+/* Substring matches against boot_cpu_data.x86_model_id; order matters. */
+static const char * const dptc_soc_table[] = {
+	/* AI MAX */
+	"AMD RYZEN AI MAX+ 395",
+	"AMD RYZEN AI MAX+ 385",
+	"AMD RYZEN AI MAX 380",
+	NULL,
+};
+
+static const struct dmi_system_id dptc_dmi_table[] = {
+	/* GPD */
+	{
+		.ident = "GPD Win 5",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "GPD"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "G1618-05"),
+		},
+		.driver_data = (void *)&limits_maxhh,
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(dmi, dptc_dmi_table);
+
+struct dptc_priv;
+
+struct dptc_attr_sysfs {
+	struct dptc_priv *priv;
+	struct kobj_attribute current_value;
+	struct kobj_attribute default_value;
+	struct kobj_attribute min_value;
+	struct kobj_attribute max_value;
+	struct kobj_attribute scalar_increment;
+	struct kobj_attribute display_name;
+	struct kobj_attribute type;
+	struct attribute *attrs[8];
+	struct attribute_group group;
+	int idx;
+};
+
+struct dptc_priv {
+	struct device *fw_attr_dev;
+	struct kset *fw_attr_kset;
+
+	const struct dptc_device_limits *dev_limits;
+
+	bool expanded;
+
+	enum dptc_save_mode { SAVE_SINGLE, SAVE_BULK } save_mode;
+
+	u32 staged[DPTC_NUM_PARAMS];
+	bool has_staged[DPTC_NUM_PARAMS];
+
+	/* Protects mutable driver state */
+	struct mutex lock;
+
+	struct dptc_attr_sysfs params[DPTC_NUM_PARAMS];
+	struct dptc_attr_sysfs expanded_attr;
+	struct kobj_attribute save_settings_attr;
+};
+
+static struct platform_device *dptc_pdev;
+
+static u32 dptc_get_min(struct dptc_priv *dptc, int idx)
+{
+	return dptc->expanded ? dptc->dev_limits->params[idx].expanded_min
+			      : dptc->dev_limits->params[idx].device_min;
+}
+
+static u32 dptc_get_max(struct dptc_priv *dptc, int idx)
+{
+	return dptc->expanded ? dptc->dev_limits->params[idx].expanded_max
+			      : dptc->dev_limits->params[idx].device_max;
+}
+
+static u32 dptc_get_default(struct dptc_priv *dptc, int idx)
+{
+	return dptc->dev_limits->params[idx].def;
+}
+
+static int dptc_alib_call(const u8 *ids, const u32 *vals, int count)
+{
+	union acpi_object in_params[2];
+	struct acpi_object_list input;
+	acpi_status status;
+	u32 buf_size;
+	int i, off;
+	u8 *buf;
+
+	if (count == 0)
+		return -EINVAL;
+
+	/* Buffer layout: WORD total_size + count * (BYTE id + DWORD value) */
+	buf_size = 2 + count * 5;
+	buf = kzalloc(buf_size, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	put_unaligned_le16(buf_size, buf);
+
+	for (i = 0; i < count; i++) {
+		off  = 2 + i * 5;
+		buf[off] = ids[i];
+		put_unaligned_le32(vals[i], buf + off + 1);
+	}
+
+	in_params[0].type          = ACPI_TYPE_INTEGER;
+	in_params[0].integer.value = ALIB_FUNC_DPTC;
+	in_params[1].type          = ACPI_TYPE_BUFFER;
+	in_params[1].buffer.length  = buf_size;
+	in_params[1].buffer.pointer = buf;
+
+	input.count   = 2;
+	input.pointer = in_params;
+
+	status = acpi_evaluate_object(NULL, ALIB_PATH, &input, NULL);
+	kfree(buf);
+
+	if (ACPI_FAILURE(status)) {
+		pr_err("ALIB call failed: %s\n",
+		       acpi_format_exception(status));
+		return -EIO;
+	}
+
+	pr_debug("sent %d ALIB parameter(s)\n", count);
+	return 0;
+}
+
+static int dptc_alib_send_one(int idx, u32 val)
+{
+	u32 hw_val = val * dptc_params[idx].scale;
+	u32 vals[2];
+	u8 ids[2];
+	int count = 0;
+
+	ids[count]  = dptc_params[idx].param_id;
+	vals[count] = hw_val;
+	count++;
+	if (dptc_params[idx].param_id2) {
+		ids[count]  = dptc_params[idx].param_id2;
+		vals[count] = hw_val;
+		count++;
+	}
+
+	return dptc_alib_call(ids, vals, count);
+}
+
+static int dptc_alib_save(struct dptc_priv *dptc)
+{
+	u32 vals[DPTC_NUM_PARAMS * 2];
+	u8 ids[DPTC_NUM_PARAMS * 2];
+	int i, count = 0;
+	u32 hw_val;
+
+	for (i = 0; i < DPTC_NUM_PARAMS; i++) {
+		if (!dptc->has_staged[i])
+			continue;
+
+		hw_val = dptc->staged[i] * dptc_params[i].scale;
+		ids[count]  = dptc_params[i].param_id;
+		vals[count] = hw_val;
+		count++;
+		if (dptc_params[i].param_id2) {
+			ids[count]  = dptc_params[i].param_id2;
+			vals[count] = hw_val;
+			count++;
+		}
+	}
+
+	return dptc_alib_call(ids, vals, count);
+}
+
+/* Sysfs callbacks */
+
+static ssize_t dptc_current_value_show(struct kobject *kobj,
+				       struct kobj_attribute *attr, char *buf)
+{
+	struct dptc_attr_sysfs *ps =
+		container_of(attr, struct dptc_attr_sysfs, current_value);
+	struct dptc_priv *dptc = ps->priv;
+
+	guard(mutex)(&dptc->lock);
+
+	if (!dptc->has_staged[ps->idx])
+		return sysfs_emit(buf, "\n");
+	return sysfs_emit(buf, "%u\n", dptc->staged[ps->idx]);
+}
+
+static ssize_t dptc_current_value_store(struct kobject *kobj,
+					struct kobj_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct dptc_attr_sysfs *ps =
+		container_of(attr, struct dptc_attr_sysfs, current_value);
+	struct dptc_priv *dptc = ps->priv;
+	u32 val, min, max;
+	int ret;
+
+	if (count == 1 && buf[0] == '\n') {
+		guard(mutex)(&dptc->lock);
+
+		dptc->has_staged[ps->idx] = false;
+		return count;
+	}
+
+	ret = kstrtou32(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	guard(mutex)(&dptc->lock);
+
+	min = dptc_get_min(dptc, ps->idx);
+	max = dptc_get_max(dptc, ps->idx);
+	if (val < min || (max && val > max))
+		return -EINVAL;
+	dptc->staged[ps->idx]    = val;
+	dptc->has_staged[ps->idx] = true;
+	if (dptc->save_mode == SAVE_SINGLE)
+		ret = dptc_alib_send_one(ps->idx, val);
+
+	return ret ? ret : count;
+}
+
+static ssize_t dptc_default_value_show(struct kobject *kobj,
+				       struct kobj_attribute *attr, char *buf)
+{
+	struct dptc_attr_sysfs *ps =
+		container_of(attr, struct dptc_attr_sysfs, default_value);
+
+	return sysfs_emit(buf, "%u\n", dptc_get_default(ps->priv, ps->idx));
+}
+
+static ssize_t dptc_min_value_show(struct kobject *kobj,
+				   struct kobj_attribute *attr, char *buf)
+{
+	struct dptc_attr_sysfs *ps =
+		container_of(attr, struct dptc_attr_sysfs, min_value);
+	struct dptc_priv *dptc = ps->priv;
+
+	guard(mutex)(&dptc->lock);
+
+	return sysfs_emit(buf, "%u\n", dptc_get_min(dptc, ps->idx));
+}
+
+static ssize_t dptc_max_value_show(struct kobject *kobj,
+				   struct kobj_attribute *attr, char *buf)
+{
+	struct dptc_attr_sysfs *ps =
+		container_of(attr, struct dptc_attr_sysfs, max_value);
+	struct dptc_priv *dptc = ps->priv;
+
+	guard(mutex)(&dptc->lock);
+
+	return sysfs_emit(buf, "%u\n", dptc_get_max(dptc, ps->idx));
+}
+
+static ssize_t dptc_scalar_increment_show(struct kobject *kobj,
+					  struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "1\n");
+}
+
+static ssize_t dptc_display_name_show(struct kobject *kobj,
+				      struct kobj_attribute *attr, char *buf)
+{
+	struct dptc_attr_sysfs *ps =
+		container_of(attr, struct dptc_attr_sysfs, display_name);
+	return sysfs_emit(buf, "%s\n", dptc_params[ps->idx].display_name);
+}
+
+static ssize_t dptc_type_show(struct kobject *kobj,
+			      struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "integer\n");
+}
+
+static ssize_t dptc_save_settings_show(struct kobject *kobj,
+				       struct kobj_attribute *attr, char *buf)
+{
+	struct dptc_priv *dptc =
+		container_of(attr, struct dptc_priv, save_settings_attr);
+
+	guard(mutex)(&dptc->lock);
+
+	if (dptc->save_mode == SAVE_SINGLE)
+		return sysfs_emit(buf, "single\n");
+	return sysfs_emit(buf, "bulk\n");
+}
+
+static ssize_t dptc_save_settings_store(struct kobject *kobj,
+					struct kobj_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct dptc_priv *dptc =
+		container_of(attr, struct dptc_priv, save_settings_attr);
+	int ret = 0;
+
+	guard(mutex)(&dptc->lock);
+
+	if (sysfs_streq(buf, "save"))
+		ret = dptc_alib_save(dptc);
+	else if (sysfs_streq(buf, "single"))
+		dptc->save_mode = SAVE_SINGLE;
+	else if (sysfs_streq(buf, "bulk"))
+		dptc->save_mode = SAVE_BULK;
+	else
+		return -EINVAL;
+
+	return ret ? ret : count;
+}
+
+static ssize_t dptc_expanded_current_value_show(struct kobject *kobj,
+						struct kobj_attribute *attr,
+						char *buf)
+{
+	struct dptc_attr_sysfs *ps =
+		container_of(attr, struct dptc_attr_sysfs, current_value);
+	struct dptc_priv *dptc = ps->priv;
+
+	guard(mutex)(&dptc->lock);
+
+	return sysfs_emit(buf, "%d\n", dptc->expanded);
+}
+
+static ssize_t dptc_expanded_current_value_store(struct kobject *kobj,
+						 struct kobj_attribute *attr,
+						 const char *buf, size_t count)
+{
+	struct dptc_attr_sysfs *ps =
+		container_of(attr, struct dptc_attr_sysfs, current_value);
+	struct dptc_priv *dptc = ps->priv;
+	bool val;
+	int ret;
+
+	ret = kstrtobool(buf, &val);
+	if (ret)
+		return ret;
+
+	guard(mutex)(&dptc->lock);
+
+	dptc->expanded = val;
+	/* Clear staged values: limits changed, old values may be out of range */
+	memset(dptc->has_staged, 0, sizeof(dptc->has_staged));
+
+	return count;
+}
+
+static ssize_t dptc_expanded_default_value_show(struct kobject *kobj,
+						struct kobj_attribute *attr,
+						char *buf)
+{
+	return sysfs_emit(buf, "0\n");
+}
+
+static ssize_t dptc_expanded_min_value_show(struct kobject *kobj,
+					    struct kobj_attribute *attr,
+					    char *buf)
+{
+	return sysfs_emit(buf, "0\n");
+}
+
+static ssize_t dptc_expanded_max_value_show(struct kobject *kobj,
+					    struct kobj_attribute *attr,
+					    char *buf)
+{
+	return sysfs_emit(buf, "1\n");
+}
+
+static ssize_t dptc_expanded_scalar_increment_show(struct kobject *kobj,
+						   struct kobj_attribute *attr,
+						   char *buf)
+{
+	return sysfs_emit(buf, "1\n");
+}
+
+static ssize_t dptc_expanded_display_name_show(struct kobject *kobj,
+					       struct kobj_attribute *attr,
+					       char *buf)
+{
+	return sysfs_emit(buf, "Expanded Limits\n");
+}
+
+static ssize_t dptc_expanded_type_show(struct kobject *kobj,
+				       struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "integer\n");
+}
+
+/* Sysfs setup */
+
+static void dptc_setup_param_sysfs(struct dptc_priv *dptc,
+				   struct dptc_attr_sysfs *ps, int idx)
+{
+	ps->priv = dptc;
+	ps->idx = idx;
+
+	sysfs_attr_init(&ps->current_value.attr);
+	ps->current_value.attr.name  = "current_value";
+	ps->current_value.attr.mode  = 0644;
+	ps->current_value.show       = dptc_current_value_show;
+	ps->current_value.store      = dptc_current_value_store;
+
+	sysfs_attr_init(&ps->default_value.attr);
+	ps->default_value.attr.name  = "default_value";
+	ps->default_value.attr.mode  = 0444;
+	ps->default_value.show       = dptc_default_value_show;
+
+	sysfs_attr_init(&ps->min_value.attr);
+	ps->min_value.attr.name      = "min_value";
+	ps->min_value.attr.mode      = 0444;
+	ps->min_value.show           = dptc_min_value_show;
+
+	sysfs_attr_init(&ps->max_value.attr);
+	ps->max_value.attr.name      = "max_value";
+	ps->max_value.attr.mode      = 0444;
+	ps->max_value.show           = dptc_max_value_show;
+
+	sysfs_attr_init(&ps->scalar_increment.attr);
+	ps->scalar_increment.attr.name = "scalar_increment";
+	ps->scalar_increment.attr.mode = 0444;
+	ps->scalar_increment.show      = dptc_scalar_increment_show;
+
+	sysfs_attr_init(&ps->display_name.attr);
+	ps->display_name.attr.name   = "display_name";
+	ps->display_name.attr.mode   = 0444;
+	ps->display_name.show        = dptc_display_name_show;
+
+	sysfs_attr_init(&ps->type.attr);
+	ps->type.attr.name           = "type";
+	ps->type.attr.mode           = 0444;
+	ps->type.show                = dptc_type_show;
+
+	ps->attrs[0] = &ps->current_value.attr;
+	ps->attrs[1] = &ps->default_value.attr;
+	ps->attrs[2] = &ps->min_value.attr;
+	ps->attrs[3] = &ps->max_value.attr;
+	ps->attrs[4] = &ps->scalar_increment.attr;
+	ps->attrs[5] = &ps->display_name.attr;
+	ps->attrs[6] = &ps->type.attr;
+	ps->attrs[7] = NULL;
+
+	ps->group.name  = dptc_params[idx].name;
+	ps->group.attrs = ps->attrs;
+}
+
+static void dptc_setup_expanded_sysfs(struct dptc_priv *dptc,
+				      struct dptc_attr_sysfs *ps)
+{
+	ps->priv = dptc;
+	sysfs_attr_init(&ps->current_value.attr);
+	ps->current_value.attr.name  = "current_value";
+	ps->current_value.attr.mode  = 0644;
+	ps->current_value.show       = dptc_expanded_current_value_show;
+	ps->current_value.store      = dptc_expanded_current_value_store;
+
+	sysfs_attr_init(&ps->default_value.attr);
+	ps->default_value.attr.name  = "default_value";
+	ps->default_value.attr.mode  = 0444;
+	ps->default_value.show       = dptc_expanded_default_value_show;
+
+	sysfs_attr_init(&ps->min_value.attr);
+	ps->min_value.attr.name      = "min_value";
+	ps->min_value.attr.mode      = 0444;
+	ps->min_value.show           = dptc_expanded_min_value_show;
+
+	sysfs_attr_init(&ps->max_value.attr);
+	ps->max_value.attr.name      = "max_value";
+	ps->max_value.attr.mode      = 0444;
+	ps->max_value.show           = dptc_expanded_max_value_show;
+
+	sysfs_attr_init(&ps->scalar_increment.attr);
+	ps->scalar_increment.attr.name = "scalar_increment";
+	ps->scalar_increment.attr.mode = 0444;
+	ps->scalar_increment.show      = dptc_expanded_scalar_increment_show;
+
+	sysfs_attr_init(&ps->display_name.attr);
+	ps->display_name.attr.name   = "display_name";
+	ps->display_name.attr.mode   = 0444;
+	ps->display_name.show        = dptc_expanded_display_name_show;
+
+	sysfs_attr_init(&ps->type.attr);
+	ps->type.attr.name           = "type";
+	ps->type.attr.mode           = 0444;
+	ps->type.show                = dptc_expanded_type_show;
+
+	ps->attrs[0] = &ps->current_value.attr;
+	ps->attrs[1] = &ps->default_value.attr;
+	ps->attrs[2] = &ps->min_value.attr;
+	ps->attrs[3] = &ps->max_value.attr;
+	ps->attrs[4] = &ps->scalar_increment.attr;
+	ps->attrs[5] = &ps->display_name.attr;
+	ps->attrs[6] = &ps->type.attr;
+	ps->attrs[7] = NULL;
+
+	ps->group.name  = "expanded_limits";
+	ps->group.attrs = ps->attrs;
+}
+
+static void dptc_fw_dev_unregister(void *data)
+{
+	device_unregister(data);
+}
+
+static void dptc_kset_unregister(void *data)
+{
+	kset_unregister(data);
+}
+
+static int dptc_resume(struct device *dev)
+{
+	struct dptc_priv *dptc = dev_get_drvdata(dev);
+	int ret;
+
+	guard(mutex)(&dptc->lock);
+
+	if (dptc->save_mode == SAVE_SINGLE)
+		ret = dptc_alib_save(dptc);
+	else
+		ret = 0;
+
+	if (ret)
+		dev_warn(dev, "failed to restore settings on resume: %d\n", ret);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(dptc_pm_ops, NULL, dptc_resume);
+
+static int dptc_probe(struct platform_device *pdev)
+{
+	const struct dmi_system_id *dmi_match = dev_get_platdata(&pdev->dev);
+	struct device *dev = &pdev->dev;
+	struct dptc_priv *dptc;
+	int i, ret;
+
+	dptc = devm_kzalloc(dev, sizeof(*dptc), GFP_KERNEL);
+	if (!dptc)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, dptc);
+
+	ret = devm_mutex_init(dev, &dptc->lock);
+	if (ret)
+		return ret;
+
+	dptc->dev_limits = dmi_match->driver_data;
+	dev_info(dev, "%s (%s)\n", dmi_match->ident,
+		 boot_cpu_data.x86_model_id);
+
+	dptc->fw_attr_dev = device_create(&firmware_attributes_class,
+					  NULL, MKDEV(0, 0), NULL,
+					  DRIVER_NAME);
+	if (IS_ERR(dptc->fw_attr_dev))
+		return PTR_ERR(dptc->fw_attr_dev);
+
+	ret = devm_add_action_or_reset(dev, dptc_fw_dev_unregister,
+				       dptc->fw_attr_dev);
+	if (ret)
+		return ret;
+
+	dptc->fw_attr_kset = kset_create_and_add("attributes", NULL,
+						 &dptc->fw_attr_dev->kobj);
+	if (!dptc->fw_attr_kset)
+		return -ENOMEM;
+
+	ret = devm_add_action_or_reset(dev, dptc_kset_unregister,
+				       dptc->fw_attr_kset);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < DPTC_NUM_PARAMS; i++) {
+		dptc_setup_param_sysfs(dptc, &dptc->params[i], i);
+		ret = sysfs_create_group(&dptc->fw_attr_kset->kobj,
+					 &dptc->params[i].group);
+		if (ret)
+			return ret;
+	}
+
+	dptc_setup_expanded_sysfs(dptc, &dptc->expanded_attr);
+	ret = sysfs_create_group(&dptc->fw_attr_kset->kobj,
+				 &dptc->expanded_attr.group);
+	if (ret)
+		return ret;
+
+	sysfs_attr_init(&dptc->save_settings_attr.attr);
+	dptc->save_settings_attr.attr.name  = "save_settings";
+	dptc->save_settings_attr.attr.mode  = 0644;
+	dptc->save_settings_attr.show       = dptc_save_settings_show;
+	dptc->save_settings_attr.store      = dptc_save_settings_store;
+	ret = sysfs_create_file(&dptc->fw_attr_kset->kobj,
+				&dptc->save_settings_attr.attr);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static struct platform_driver dptc_driver = {
+	.driver = {
+		.name = DRIVER_NAME,
+		.pm   = pm_sleep_ptr(&dptc_pm_ops),
+	},
+	.probe  = dptc_probe,
+};
+
+static int __init dptc_init(void)
+{
+	const struct dmi_system_id *match;
+	bool soc_found = false;
+	int i, ret;
+
+	match = dmi_first_match(dptc_dmi_table);
+	if (!match)
+		return -ENODEV;
+
+	if (!acpi_has_method(NULL, ALIB_PATH)) {
+		pr_warn("ALIB method not present\n");
+		return -ENODEV;
+	}
+
+	for (i = 0; dptc_soc_table[i]; i++) {
+		if (strstr(boot_cpu_data.x86_model_id,
+			   dptc_soc_table[i])) {
+			soc_found = true;
+			break;
+		}
+	}
+	if (!soc_found) {
+		pr_warn("unrecognized SoC '%s'\n",
+			boot_cpu_data.x86_model_id);
+		return -ENODEV;
+	}
+
+	dptc_pdev = platform_device_register_data(NULL, DRIVER_NAME, -1,
+						  match, sizeof(*match));
+	if (IS_ERR(dptc_pdev))
+		return PTR_ERR(dptc_pdev);
+
+	ret = platform_driver_register(&dptc_driver);
+	if (ret) {
+		platform_device_unregister(dptc_pdev);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __exit dptc_exit(void)
+{
+	platform_driver_unregister(&dptc_driver);
+	platform_device_unregister(dptc_pdev);
+}
+
+module_init(dptc_init);
+module_exit(dptc_exit);
+
+MODULE_AUTHOR("Antheas Kapenekakis <lkml@antheas.dev>");
+MODULE_DESCRIPTION("AMD DPTCi ACPI Driver");
+MODULE_LICENSE("GPL");
-- 
2.52.0

Hi Antheas,

Thanks for working on it.

I think this driver is useful for me and I will see if I can test it on
my devices once I find some time. They're not handhelds but I am sure
at least one of them has the ALIB method. It'd better if a module
option can be used to bypass the quirk table so that testing against a
new device will be easier. Such an option should taint the kernel ofc.

That being said, I have some review comments. Please see below and my
following replies.

On Sat, 2026-03-07 at 12:55 +0100, Antheas Kapenekakis wrote:
> Add a driver for AMD AGESA ALIB Function 0x0C, the Dynamic Power and
> Thermal Configuration interface (DPTCi). This exposes TDP and thermal
> parameters for AMD APU-based handheld devices via the
> firmware-attributes sysfs ABI.
> 
> Parameters are staged and atomically committed through ALIB. The driver
> supports two save modes: "single" (apply immediately on write) and
> "bulk" (stage values, then commit with "save"). An "expanded_limits"
> toggle widens the allowed parameter ranges beyond device defaults.
> 
> Initial device support: GPD Win 5 (AMD Ryzen AI MAX).
> 
> Assisted-by: Claude:claude-opus-4-6
> Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
> ---
>  MAINTAINERS                       |   6 +
>  drivers/platform/x86/amd/Kconfig  |  14 +
>  drivers/platform/x86/amd/Makefile |   2 +
>  drivers/platform/x86/amd/dptc.c   | 747 ++++++++++++++++++++++++++++++
>  4 files changed, 769 insertions(+)
>  create mode 100644 drivers/platform/x86/amd/dptc.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e08767323763..915293594641 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1096,6 +1096,12 @@ S:	Supported
>  F:	drivers/gpu/drm/amd/display/dc/dml/
>  F:	drivers/gpu/drm/amd/display/dc/dml2_0/
>  
> +AMD DPTC DRIVER
> +M:	Antheas Kapenekakis <lkml@antheas.dev>
> +L:	platform-driver-x86@vger.kernel.org
> +S:	Maintained
> +F:	drivers/platform/x86/amd/dptc.c
> +
>  AMD FAM15H PROCESSOR POWER MONITORING DRIVER
>  M:	Huang Rui <ray.huang@amd.com>
>  L:	linux-hwmon@vger.kernel.org
> diff --git a/drivers/platform/x86/amd/Kconfig b/drivers/platform/x86/amd/Kconfig
> index b813f9265368..d610092467fc 100644
> --- a/drivers/platform/x86/amd/Kconfig
> +++ b/drivers/platform/x86/amd/Kconfig
> @@ -44,3 +44,17 @@ config AMD_ISP_PLATFORM
>  
>  	  This driver can also be built as a module. If so, the module
>  	  will be called amd_isp4.
> +
> +config AMD_DPTC
> +	tristate "AMD Dynamic Power and Thermal Configuration Interface (DPTCi)"
> +	depends on X86_64 && ACPI && DMI
> +	select FIRMWARE_ATTRIBUTES_CLASS
> +	help
> +	  Driver for AMD AGESA ALIB Function 0x0C, the Dynamic Power and
> +	  Thermal Configuration Interface (DPTCi). Exposes TDP and thermal
> +	  parameters for AMD APU-based handheld devices via the
> +	  firmware-attributes sysfs ABI, allowing userspace tools to stage
> +	  and atomically commit power limit settings. Requires a DMI match
> +	  for the device and a recognized AMD SoC.
> +
> +	  If built as a module, the module will be called amd_dptc.
> diff --git a/drivers/platform/x86/amd/Makefile b/drivers/platform/x86/amd/Makefile
> index f6ff0c837f34..862a609bfe38 100644
> --- a/drivers/platform/x86/amd/Makefile
> +++ b/drivers/platform/x86/amd/Makefile
> @@ -12,3 +12,5 @@ obj-$(CONFIG_AMD_PMF)		+= pmf/
>  obj-$(CONFIG_AMD_WBRF)		+= wbrf.o
>  obj-$(CONFIG_AMD_ISP_PLATFORM)	+= amd_isp4.o
>  obj-$(CONFIG_AMD_HFI)		+= hfi/
> +obj-$(CONFIG_AMD_DPTC)		+= amd_dptc.o
> +amd_dptc-y			:= dptc.o
> diff --git a/drivers/platform/x86/amd/dptc.c b/drivers/platform/x86/amd/dptc.c
> new file mode 100644
> index 000000000000..acfe9cc01bab
> --- /dev/null
> +++ b/drivers/platform/x86/amd/dptc.c
> @@ -0,0 +1,747 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * AMD Dynamic Power and Thermal Configuration Interface (DPTCi) driver
> + *
> + * Exposes AMD APU power and thermal parameters via the firmware-attributes
> + * sysfs ABI. Parameters are staged and atomically committed through the
> + * AGESA ALIB Function 0x0C (Dynamic Power and Thermal Configuration
> + * interface).
> + *
> + * Reference: AMD AGESA Publication #44065, Appendix E.5
> + *            https://docs.amd.com/v/u/en-US/44065_Arch2008
> + *
> + * Copyright (C) 2026 Antheas Kapenekakis <lkml@antheas.dev>
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/acpi.h>
> +#include <linux/cleanup.h>
> +#include <linux/dmi.h>
> +#include <linux/init.h>
> +#include <linux/kobject.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/platform_device.h>
> +#include <linux/processor.h>
> +#include <linux/sysfs.h>
> +#include <linux/unaligned.h>
> +
> +#include "../firmware_attributes_class.h"
> +
> +#define DRIVER_NAME		"amd-dptc"
> +
> +#define ALIB_FUNC_DPTC		0x0C
> +#define ALIB_PATH		"\\_SB.ALIB"
> +
> +#define ALIB_ID_TEMP_TARGET	0x03
> +#define ALIB_ID_STAPM_LIMIT	0x05
> +#define ALIB_ID_FAST_LIMIT	0x06
> +#define ALIB_ID_SLOW_LIMIT	0x07
> +#define ALIB_ID_SKIN_LIMIT	0x2E
> +
> +enum dptc_param_idx {
> +	DPTC_PPT_PL1_SPL,	/* STAPM + skin limit (set together) */
> +	DPTC_PPT_PL2_SPPT,	/* slow PPT limit */
> +	DPTC_PPT_PL3_FPPT,	/* fast PPT limit */
> +	DPTC_CPU_TEMP,		/* thermal control target */
> +	DPTC_NUM_PARAMS,
> +};
> +
> +struct dptc_param_limits {
> +	u32 expanded_min;
> +	u32 device_min;
> +	u32 def;
> +	u32 device_max;
> +	u32 expanded_max;
> +};
> +
> +struct dptc_device_limits {
> +	struct dptc_param_limits params[DPTC_NUM_PARAMS];
> +};
> +
> +struct dptc_param_desc {
> +	const char *name;
> +	const char *display_name;
> +	u16 scale;	/* sysfs-to-ALIB multiplier (e.g. 1000 for W->mW) */
> +	u8 param_id;
> +	u8 param_id2;	/* secondary ALIB ID, 0 if none */
> +};
> +
> +static const struct dptc_param_desc dptc_params[DPTC_NUM_PARAMS] = {
> +	[DPTC_PPT_PL1_SPL]  = { "ppt_pl1_spl",  "Sustained power limit (W)",
> +		1000, ALIB_ID_STAPM_LIMIT, ALIB_ID_SKIN_LIMIT },
> +	[DPTC_PPT_PL2_SPPT] = { "ppt_pl2_sppt", "Slow PPT limit (W)",
> +		1000, ALIB_ID_SLOW_LIMIT },
> +	[DPTC_PPT_PL3_FPPT] = { "ppt_pl3_fppt", "Fast PPT limit (W)",
> +		1000, ALIB_ID_FAST_LIMIT },
> +	[DPTC_CPU_TEMP]     = { "cpu_temp",     "Thermal control limit (C)",
> +		   1, ALIB_ID_TEMP_TARGET },
> +};

The indent here just made me crazy :-/

Align the contents after line breaks to the left braces.

> +
> +/* AI MAX Handheld class: GPD Win 5 */
> +static const struct dptc_device_limits limits_maxhh = { .params = {

Please don't save a line by zipping braces like this. It's hard to read
and likely to be missed when glancing the code (that's what happened to
me and it really confused me).

I found you did the same in [PATCH v3 3/4] for `.profiles'. That should
be avoided too.

> +	[DPTC_PPT_PL1_SPL]  = {  0,  4, 25,  80, 100 },
> +	[DPTC_PPT_PL2_SPPT] = {  0,  4, 27,  82, 100 },
> +	[DPTC_PPT_PL3_FPPT] = {  0,  4, 40,  85, 100 },
> +	[DPTC_CPU_TEMP]     = { 60, 70, 95,  95, 100 },
> +}};
> +
> +/* Substring matches against boot_cpu_data.x86_model_id; order matters. */
> +static const char * const dptc_soc_table[] = {
> +	/* AI MAX */
> +	"AMD RYZEN AI MAX+ 395",
> +	"AMD RYZEN AI MAX+ 385",
> +	"AMD RYZEN AI MAX 380",
> +	NULL,
> +};
> +
> +static const struct dmi_system_id dptc_dmi_table[] = {
> +	/* GPD */
> +	{
> +		.ident = "GPD Win 5",
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "GPD"),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "G1618-05"),
> +		},
> +		.driver_data = (void *)&limits_maxhh,
> +	},
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(dmi, dptc_dmi_table);
> +
> +struct dptc_priv;
> +
> +struct dptc_attr_sysfs {
> +	struct dptc_priv *priv;
> +	struct kobj_attribute current_value;
> +	struct kobj_attribute default_value;
> +	struct kobj_attribute min_value;
> +	struct kobj_attribute max_value;
> +	struct kobj_attribute scalar_increment;
> +	struct kobj_attribute display_name;
> +	struct kobj_attribute type;
> +	struct attribute *attrs[8];
> +	struct attribute_group group;
> +	int idx;
> +};
> +
> +struct dptc_priv {
> +	struct device *fw_attr_dev;
> +	struct kset *fw_attr_kset;
> +
> +	const struct dptc_device_limits *dev_limits;
> +
> +	bool expanded;
> +
> +	enum dptc_save_mode { SAVE_SINGLE, SAVE_BULK } save_mode;

Defining the enumeration separately will improve readability.

> +
> +	u32 staged[DPTC_NUM_PARAMS];
> +	bool has_staged[DPTC_NUM_PARAMS];
> +
> +	/* Protects mutable driver state */

The comment is nonsense. To make it helpful, it should be "Protects
members above/below" with properly arranged structure layout.

> +	struct mutex lock;
> +
> +	struct dptc_attr_sysfs params[DPTC_NUM_PARAMS];
> +	struct dptc_attr_sysfs expanded_attr;
> +	struct kobj_attribute save_settings_attr;
> +};
> +
> +static struct platform_device *dptc_pdev;
> +
> +static u32 dptc_get_min(struct dptc_priv *dptc, int idx)
> +{
> +	return dptc->expanded ? dptc->dev_limits->params[idx].expanded_min
> +			      : dptc->dev_limits->params[idx].device_min;
> +}
> +
> +static u32 dptc_get_max(struct dptc_priv *dptc, int idx)
> +{
> +	return dptc->expanded ? dptc->dev_limits->params[idx].expanded_max
> +			      : dptc->dev_limits->params[idx].device_max;
> +}
> +
> +static u32 dptc_get_default(struct dptc_priv *dptc, int idx)
> +{
> +	return dptc->dev_limits->params[idx].def;
> +}
> +
> +static int dptc_alib_call(const u8 *ids, const u32 *vals, int count)
> +{
> +	union acpi_object in_params[2];
> +	struct acpi_object_list input;
> +	acpi_status status;
> +	u32 buf_size;
> +	int i, off;
> +	u8 *buf;
> +
> +	if (count == 0)
> +		return -EINVAL;

Return -ENOENT as think-lmi does (see its save_settings_store()) and
update the documentation accordingly.

> +
> +	/* Buffer layout: WORD total_size + count * (BYTE id + DWORD value) */
> +	buf_size = 2 + count * 5;
> +	buf = kzalloc(buf_size, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	put_unaligned_le16(buf_size, buf);
> +
> +	for (i = 0; i < count; i++) {
> +		off  = 2 + i * 5;
> +		buf[off] = ids[i];
> +		put_unaligned_le32(vals[i], buf + off + 1);

put_unaligned_le32(vals[i], &buf[off + 1]);

> +	}
> +
> +	in_params[0].type          = ACPI_TYPE_INTEGER;
> +	in_params[0].integer.value = ALIB_FUNC_DPTC;
> +	in_params[1].type          = ACPI_TYPE_BUFFER;
> +	in_params[1].buffer.length  = buf_size;
> +	in_params[1].buffer.pointer = buf;

Misaligned `='.

> +
> +	input.count   = 2;
> +	input.pointer = in_params;
> +
> +	status = acpi_evaluate_object(NULL, ALIB_PATH, &input, NULL);
> +	kfree(buf);
> +
> +	if (ACPI_FAILURE(status)) {
> +		pr_err("ALIB call failed: %s\n",
> +		       acpi_format_exception(status));
> +		return -EIO;
> +	}
> +
> +	pr_debug("sent %d ALIB parameter(s)\n", count);
> +	return 0;
> +}
> +
> +static int dptc_alib_send_one(int idx, u32 val)
> +{
> +	u32 hw_val = val * dptc_params[idx].scale;
> +	u32 vals[2];
> +	u8 ids[2];
> +	int count = 0;
> +
> +	ids[count]  = dptc_params[idx].param_id;
> +	vals[count] = hw_val;
> +	count++;
> +	if (dptc_params[idx].param_id2) {
> +		ids[count]  = dptc_params[idx].param_id2;
> +		vals[count] = hw_val;
> +		count++;
> +	}
> +
> +	return dptc_alib_call(ids, vals, count);
> +}
> +
> +static int dptc_alib_save(struct dptc_priv *dptc)
> +{
> +	u32 vals[DPTC_NUM_PARAMS * 2];
> +	u8 ids[DPTC_NUM_PARAMS * 2];
> +	int i, count = 0;
> +	u32 hw_val;
> +
> +	for (i = 0; i < DPTC_NUM_PARAMS; i++) {
> +		if (!dptc->has_staged[i])
> +			continue;
> +
> +		hw_val = dptc->staged[i] * dptc_params[i].scale;
> +		ids[count]  = dptc_params[i].param_id;
> +		vals[count] = hw_val;
> +		count++;
> +		if (dptc_params[i].param_id2) {
> +			ids[count]  = dptc_params[i].param_id2;
> +			vals[count] = hw_val;
> +			count++;
> +		}

I could imagine a helper function to prevent replicating the same code
patterns twice:

static size_t dptc_alib_fill_param(u8 *ids, u32 *vals, size_t offset,
				   enum dptc_param_idx param, u32 val)
{
	u32 hw_val = val * dptc_params[param].scale;

	ids[offset]    = dptc_params[param].param_id;
	vals[offset++] = hw_val;

	if (dptc_params[param].param_id2) {
		ids[offset]    = dptc_params[param].param_id2;
		vals[offset++] = hw_val;
	}

	return offset;
}

> +	}
> +
> +	return dptc_alib_call(ids, vals, count);
> +}
> +
> +/* Sysfs callbacks */
> +
> +static ssize_t dptc_current_value_show(struct kobject *kobj,
> +				       struct kobj_attribute *attr, char *buf)
> +{
> +	struct dptc_attr_sysfs *ps =
> +		container_of(attr, struct dptc_attr_sysfs, current_value);
> +	struct dptc_priv *dptc = ps->priv;
> +
> +	guard(mutex)(&dptc->lock);
> +
> +	if (!dptc->has_staged[ps->idx])
> +		return sysfs_emit(buf, "\n");
> +	return sysfs_emit(buf, "%u\n", dptc->staged[ps->idx]);
> +}
> +
> +static ssize_t dptc_current_value_store(struct kobject *kobj,
> +					struct kobj_attribute *attr,
> +					const char *buf, size_t count)
> +{
> +	struct dptc_attr_sysfs *ps =
> +		container_of(attr, struct dptc_attr_sysfs, current_value);
> +	struct dptc_priv *dptc = ps->priv;
> +	u32 val, min, max;
> +	int ret;
> +
> +	if (count == 1 && buf[0] == '\n') {
> +		guard(mutex)(&dptc->lock);
> +
> +		dptc->has_staged[ps->idx] = false;
> +		return count;
> +	}
> +
> +	ret = kstrtou32(buf, 10, &val);
> +	if (ret)
> +		return ret;
> +
> +	guard(mutex)(&dptc->lock);
> +
> +	min = dptc_get_min(dptc, ps->idx);
> +	max = dptc_get_max(dptc, ps->idx);
> +	if (val < min || (max && val > max))
> +		return -EINVAL;
> +	dptc->staged[ps->idx]    = val;
> +	dptc->has_staged[ps->idx] = true;
> +	if (dptc->save_mode == SAVE_SINGLE)
> +		ret = dptc_alib_send_one(ps->idx, val);
> +
> +	return ret ? ret : count;
> +}
> +
> +static ssize_t dptc_default_value_show(struct kobject *kobj,
> +				       struct kobj_attribute *attr, char *buf)
> +{
> +	struct dptc_attr_sysfs *ps =
> +		container_of(attr, struct dptc_attr_sysfs, default_value);
> +
> +	return sysfs_emit(buf, "%u\n", dptc_get_default(ps->priv, ps->idx));
> +}
> +
> +static ssize_t dptc_min_value_show(struct kobject *kobj,
> +				   struct kobj_attribute *attr, char *buf)
> +{
> +	struct dptc_attr_sysfs *ps =
> +		container_of(attr, struct dptc_attr_sysfs, min_value);
> +	struct dptc_priv *dptc = ps->priv;
> +
> +	guard(mutex)(&dptc->lock);
> +
> +	return sysfs_emit(buf, "%u\n", dptc_get_min(dptc, ps->idx));
> +}
> +
> +static ssize_t dptc_max_value_show(struct kobject *kobj,
> +				   struct kobj_attribute *attr, char *buf)
> +{
> +	struct dptc_attr_sysfs *ps =
> +		container_of(attr, struct dptc_attr_sysfs, max_value);
> +	struct dptc_priv *dptc = ps->priv;
> +
> +	guard(mutex)(&dptc->lock);
> +
> +	return sysfs_emit(buf, "%u\n", dptc_get_max(dptc, ps->idx));
> +}
> +
> +static ssize_t dptc_scalar_increment_show(struct kobject *kobj,
> +					  struct kobj_attribute *attr, char *buf)
> +{
> +	return sysfs_emit(buf, "1\n");
> +}
> +
> +static ssize_t dptc_display_name_show(struct kobject *kobj,
> +				      struct kobj_attribute *attr, char *buf)
> +{
> +	struct dptc_attr_sysfs *ps =
> +		container_of(attr, struct dptc_attr_sysfs, display_name);
> +	return sysfs_emit(buf, "%s\n", dptc_params[ps->idx].display_name);
> +}
> +
> +static ssize_t dptc_type_show(struct kobject *kobj,
> +			      struct kobj_attribute *attr, char *buf)
> +{
> +	return sysfs_emit(buf, "integer\n");
> +}
> +
> +static ssize_t dptc_save_settings_show(struct kobject *kobj,
> +				       struct kobj_attribute *attr, char *buf)
> +{
> +	struct dptc_priv *dptc =
> +		container_of(attr, struct dptc_priv, save_settings_attr);
> +
> +	guard(mutex)(&dptc->lock);
> +
> +	if (dptc->save_mode == SAVE_SINGLE)
> +		return sysfs_emit(buf, "single\n");
> +	return sysfs_emit(buf, "bulk\n");
> +}
> +
> +static ssize_t dptc_save_settings_store(struct kobject *kobj,
> +					struct kobj_attribute *attr,
> +					const char *buf, size_t count)
> +{
> +	struct dptc_priv *dptc =
> +		container_of(attr, struct dptc_priv, save_settings_attr);
> +	int ret = 0;
> +
> +	guard(mutex)(&dptc->lock);
> +
> +	if (sysfs_streq(buf, "save"))

Please don't rely on the `count == 0' check in dptc_alib_call(). `dptc-
>save_mode == SAVE_SINGLE' should result in -EOPNOTSUPP to maintain
consistency with think-lmi (update the documentation accordingly).

> +		ret = dptc_alib_save(dptc);
> +	else if (sysfs_streq(buf, "single"))
> +		dptc->save_mode = SAVE_SINGLE;
> +	else if (sysfs_streq(buf, "bulk"))
> +		dptc->save_mode = SAVE_BULK;
> +	else
> +		return -EINVAL;
> +
> +	return ret ? ret : count;
> +}
> +
> +static ssize_t dptc_expanded_current_value_show(struct kobject *kobj,
> +						struct kobj_attribute *attr,
> +						char *buf)
> +{
> +	struct dptc_attr_sysfs *ps =
> +		container_of(attr, struct dptc_attr_sysfs, current_value);
> +	struct dptc_priv *dptc = ps->priv;
> +
> +	guard(mutex)(&dptc->lock);
> +
> +	return sysfs_emit(buf, "%d\n", dptc->expanded);
> +}
> +
> +static ssize_t dptc_expanded_current_value_store(struct kobject *kobj,
> +						 struct kobj_attribute *attr,
> +						 const char *buf, size_t count)
> +{
> +	struct dptc_attr_sysfs *ps =
> +		container_of(attr, struct dptc_attr_sysfs, current_value);
> +	struct dptc_priv *dptc = ps->priv;
> +	bool val;
> +	int ret;
> +
> +	ret = kstrtobool(buf, &val);
> +	if (ret)
> +		return ret;
> +
> +	guard(mutex)(&dptc->lock);
> +
> +	dptc->expanded = val;
> +	/* Clear staged values: limits changed, old values may be out of range */
> +	memset(dptc->has_staged, 0, sizeof(dptc->has_staged));

I'd prefer using a bitmap so that you don't need to use memset() to
clear them. It also saves some memory if more parameters are added in
the future.

> +
> +	return count;
> +}
> +
> +static ssize_t dptc_expanded_default_value_show(struct kobject *kobj,
> +						struct kobj_attribute *attr,
> +						char *buf)
> +{
> +	return sysfs_emit(buf, "0\n");
> +}
> +
> +static ssize_t dptc_expanded_min_value_show(struct kobject *kobj,
> +					    struct kobj_attribute *attr,
> +					    char *buf)
> +{
> +	return sysfs_emit(buf, "0\n");
> +}
> +
> +static ssize_t dptc_expanded_max_value_show(struct kobject *kobj,
> +					    struct kobj_attribute *attr,
> +					    char *buf)
> +{
> +	return sysfs_emit(buf, "1\n");
> +}
> +
> +static ssize_t dptc_expanded_scalar_increment_show(struct kobject *kobj,
> +						   struct kobj_attribute *attr,
> +						   char *buf)
> +{
> +	return sysfs_emit(buf, "1\n");
> +}
> +
> +static ssize_t dptc_expanded_display_name_show(struct kobject *kobj,
> +					       struct kobj_attribute *attr,
> +					       char *buf)
> +{
> +	return sysfs_emit(buf, "Expanded Limits\n");
> +}
> +
> +static ssize_t dptc_expanded_type_show(struct kobject *kobj,
> +				       struct kobj_attribute *attr, char *buf)
> +{
> +	return sysfs_emit(buf, "integer\n");
> +}
> +
> +/* Sysfs setup */
> +
> +static void dptc_setup_param_sysfs(struct dptc_priv *dptc,
> +				   struct dptc_attr_sysfs *ps, int idx)
> +{
> +	ps->priv = dptc;
> +	ps->idx = idx;
> +
> +	sysfs_attr_init(&ps->current_value.attr);
> +	ps->current_value.attr.name  = "current_value";
> +	ps->current_value.attr.mode  = 0644;
> +	ps->current_value.show       = dptc_current_value_show;
> +	ps->current_value.store      = dptc_current_value_store;
> +
> +	sysfs_attr_init(&ps->default_value.attr);
> +	ps->default_value.attr.name  = "default_value";
> +	ps->default_value.attr.mode  = 0444;
> +	ps->default_value.show       = dptc_default_value_show;
> +
> +	sysfs_attr_init(&ps->min_value.attr);
> +	ps->min_value.attr.name      = "min_value";
> +	ps->min_value.attr.mode      = 0444;
> +	ps->min_value.show           = dptc_min_value_show;
> +
> +	sysfs_attr_init(&ps->max_value.attr);
> +	ps->max_value.attr.name      = "max_value";
> +	ps->max_value.attr.mode      = 0444;
> +	ps->max_value.show           = dptc_max_value_show;
> +
> +	sysfs_attr_init(&ps->scalar_increment.attr);
> +	ps->scalar_increment.attr.name = "scalar_increment";
> +	ps->scalar_increment.attr.mode = 0444;
> +	ps->scalar_increment.show      = dptc_scalar_increment_show;
> +
> +	sysfs_attr_init(&ps->display_name.attr);
> +	ps->display_name.attr.name   = "display_name";
> +	ps->display_name.attr.mode   = 0444;
> +	ps->display_name.show        = dptc_display_name_show;
> +
> +	sysfs_attr_init(&ps->type.attr);
> +	ps->type.attr.name           = "type";
> +	ps->type.attr.mode           = 0444;
> +	ps->type.show                = dptc_type_show;
> +
> +	ps->attrs[0] = &ps->current_value.attr;
> +	ps->attrs[1] = &ps->default_value.attr;
> +	ps->attrs[2] = &ps->min_value.attr;
> +	ps->attrs[3] = &ps->max_value.attr;
> +	ps->attrs[4] = &ps->scalar_increment.attr;
> +	ps->attrs[5] = &ps->display_name.attr;
> +	ps->attrs[6] = &ps->type.attr;
> +	ps->attrs[7] = NULL;
> +
> +	ps->group.name  = dptc_params[idx].name;
> +	ps->group.attrs = ps->attrs;
> +}
> +
> +static void dptc_setup_expanded_sysfs(struct dptc_priv *dptc,
> +				      struct dptc_attr_sysfs *ps)
> +{
> +	ps->priv = dptc;
> +	sysfs_attr_init(&ps->current_value.attr);
> +	ps->current_value.attr.name  = "current_value";
> +	ps->current_value.attr.mode  = 0644;
> +	ps->current_value.show       = dptc_expanded_current_value_show;
> +	ps->current_value.store      = dptc_expanded_current_value_store;
> +
> +	sysfs_attr_init(&ps->default_value.attr);
> +	ps->default_value.attr.name  = "default_value";
> +	ps->default_value.attr.mode  = 0444;
> +	ps->default_value.show       = dptc_expanded_default_value_show;
> +
> +	sysfs_attr_init(&ps->min_value.attr);
> +	ps->min_value.attr.name      = "min_value";
> +	ps->min_value.attr.mode      = 0444;
> +	ps->min_value.show           = dptc_expanded_min_value_show;
> +
> +	sysfs_attr_init(&ps->max_value.attr);
> +	ps->max_value.attr.name      = "max_value";
> +	ps->max_value.attr.mode      = 0444;
> +	ps->max_value.show           = dptc_expanded_max_value_show;
> +
> +	sysfs_attr_init(&ps->scalar_increment.attr);
> +	ps->scalar_increment.attr.name = "scalar_increment";
> +	ps->scalar_increment.attr.mode = 0444;
> +	ps->scalar_increment.show      = dptc_expanded_scalar_increment_show;
> +
> +	sysfs_attr_init(&ps->display_name.attr);
> +	ps->display_name.attr.name   = "display_name";
> +	ps->display_name.attr.mode   = 0444;
> +	ps->display_name.show        = dptc_expanded_display_name_show;
> +
> +	sysfs_attr_init(&ps->type.attr);
> +	ps->type.attr.name           = "type";
> +	ps->type.attr.mode           = 0444;
> +	ps->type.show                = dptc_expanded_type_show;
> +
> +	ps->attrs[0] = &ps->current_value.attr;
> +	ps->attrs[1] = &ps->default_value.attr;
> +	ps->attrs[2] = &ps->min_value.attr;
> +	ps->attrs[3] = &ps->max_value.attr;
> +	ps->attrs[4] = &ps->scalar_increment.attr;
> +	ps->attrs[5] = &ps->display_name.attr;
> +	ps->attrs[6] = &ps->type.attr;
> +	ps->attrs[7] = NULL;
> +
> +	ps->group.name  = "expanded_limits";
> +	ps->group.attrs = ps->attrs;
> +}

As Derek has said in v2, use macros to rearrange them.

It's painful to read all these things as I'll need to scroll the screen
quite a lot just to read something with a low information density.
That's why there are numerous macros defined in include/linux/sysfs.h.
I could imagine defining macros like DPTC{,_EXPANDED}_ATTR_{RO,RW}.

Meanwhile, I am not very sure why you would have to dynamically
initialize all these attributes. I haven't notice a blocker of defining
them statically at the module-level (see how lenovo-wmi-other did). Am
I missing anything?

> +
> +static void dptc_fw_dev_unregister(void *data)
> +{
> +	device_unregister(data);
> +}
> +
> +static void dptc_kset_unregister(void *data)
> +{
> +	kset_unregister(data);
> +}
> +
> +static int dptc_resume(struct device *dev)
> +{
> +	struct dptc_priv *dptc = dev_get_drvdata(dev);
> +	int ret;
> +
> +	guard(mutex)(&dptc->lock);
> +
> +	if (dptc->save_mode == SAVE_SINGLE)
> +		ret = dptc_alib_save(dptc);

I don't see why bulk mode and single mode should have divergence on
resuming behavior.

Thanks,
Rong

> +	else
> +		ret = 0;
> +
> +	if (ret)
> +		dev_warn(dev, "failed to restore settings on resume: %d\n", ret);
> +
> +	return 0;
> +}
> +
> +static DEFINE_SIMPLE_DEV_PM_OPS(dptc_pm_ops, NULL, dptc_resume);
> +
> +static int dptc_probe(struct platform_device *pdev)
> +{
> +	const struct dmi_system_id *dmi_match = dev_get_platdata(&pdev->dev);
> +	struct device *dev = &pdev->dev;
> +	struct dptc_priv *dptc;
> +	int i, ret;
> +
> +	dptc = devm_kzalloc(dev, sizeof(*dptc), GFP_KERNEL);
> +	if (!dptc)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, dptc);
> +
> +	ret = devm_mutex_init(dev, &dptc->lock);
> +	if (ret)
> +		return ret;
> +
> +	dptc->dev_limits = dmi_match->driver_data;
> +	dev_info(dev, "%s (%s)\n", dmi_match->ident,
> +		 boot_cpu_data.x86_model_id);
> +
> +	dptc->fw_attr_dev = device_create(&firmware_attributes_class,
> +					  NULL, MKDEV(0, 0), NULL,
> +					  DRIVER_NAME);
> +	if (IS_ERR(dptc->fw_attr_dev))
> +		return PTR_ERR(dptc->fw_attr_dev);
> +
> +	ret = devm_add_action_or_reset(dev, dptc_fw_dev_unregister,
> +				       dptc->fw_attr_dev);
> +	if (ret)
> +		return ret;
> +
> +	dptc->fw_attr_kset = kset_create_and_add("attributes", NULL,
> +						 &dptc->fw_attr_dev->kobj);
> +	if (!dptc->fw_attr_kset)
> +		return -ENOMEM;
> +
> +	ret = devm_add_action_or_reset(dev, dptc_kset_unregister,
> +				       dptc->fw_attr_kset);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i < DPTC_NUM_PARAMS; i++) {
> +		dptc_setup_param_sysfs(dptc, &dptc->params[i], i);
> +		ret = sysfs_create_group(&dptc->fw_attr_kset->kobj,
> +					 &dptc->params[i].group);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	dptc_setup_expanded_sysfs(dptc, &dptc->expanded_attr);
> +	ret = sysfs_create_group(&dptc->fw_attr_kset->kobj,
> +				 &dptc->expanded_attr.group);
> +	if (ret)
> +		return ret;
> +
> +	sysfs_attr_init(&dptc->save_settings_attr.attr);
> +	dptc->save_settings_attr.attr.name  = "save_settings";
> +	dptc->save_settings_attr.attr.mode  = 0644;
> +	dptc->save_settings_attr.show       = dptc_save_settings_show;
> +	dptc->save_settings_attr.store      = dptc_save_settings_store;
> +	ret = sysfs_create_file(&dptc->fw_attr_kset->kobj,
> +				&dptc->save_settings_attr.attr);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +static struct platform_driver dptc_driver = {
> +	.driver = {
> +		.name = DRIVER_NAME,
> +		.pm   = pm_sleep_ptr(&dptc_pm_ops),
> +	},
> +	.probe  = dptc_probe,
> +};
> +
> +static int __init dptc_init(void)
> +{
> +	const struct dmi_system_id *match;
> +	bool soc_found = false;
> +	int i, ret;
> +
> +	match = dmi_first_match(dptc_dmi_table);
> +	if (!match)
> +		return -ENODEV;
> +
> +	if (!acpi_has_method(NULL, ALIB_PATH)) {
> +		pr_warn("ALIB method not present\n");
> +		return -ENODEV;
> +	}
> +
> +	for (i = 0; dptc_soc_table[i]; i++) {
> +		if (strstr(boot_cpu_data.x86_model_id,
> +			   dptc_soc_table[i])) {
> +			soc_found = true;
> +			break;
> +		}
> +	}
> +	if (!soc_found) {
> +		pr_warn("unrecognized SoC '%s'\n",
> +			boot_cpu_data.x86_model_id);
> +		return -ENODEV;
> +	}
> +
> +	dptc_pdev = platform_device_register_data(NULL, DRIVER_NAME, -1,
> +						  match, sizeof(*match));
> +	if (IS_ERR(dptc_pdev))
> +		return PTR_ERR(dptc_pdev);
> +
> +	ret = platform_driver_register(&dptc_driver);
> +	if (ret) {
> +		platform_device_unregister(dptc_pdev);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static void __exit dptc_exit(void)
> +{
> +	platform_driver_unregister(&dptc_driver);
> +	platform_device_unregister(dptc_pdev);
> +}
> +
> +module_init(dptc_init);
> +module_exit(dptc_exit);
> +
> +MODULE_AUTHOR("Antheas Kapenekakis <lkml@antheas.dev>");
> +MODULE_DESCRIPTION("AMD DPTCi ACPI Driver");
> +MODULE_LICENSE("GPL");