Add a uma/ directory containing two sysfs files as interfaces to
inspect or change UMA carveout size. These files are:

- uma/carveout_options: a read-only file listing all the available
  UMA allocation options and their index.

- uma/carveout: a file that is both readable and writable. On read,
  it shows the index of the current setting. Writing a valid index
  into this file allows users to change the UMA carveout size to that
  option on the next boot.

Co-developed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 139 +++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index bce9027fa241..2c0405cdc436 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -30,6 +30,8 @@
 #include <linux/power_supply.h>
 #include <linux/pm_runtime.h>
 #include <linux/suspend.h>
+#include <linux/device.h>
+#include <linux/nospec.h>
 #include <acpi/video.h>
 #include <acpi/actbl.h>
 
@@ -1246,6 +1248,136 @@ int amdgpu_acpi_get_mem_info(struct amdgpu_device *adev, int xcc_id,
 	return -ENOENT;
 }
 
+static ssize_t carveout_options_show(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
+	uint32_t memory_carved;
+	ssize_t size = 0;
+
+	if (!uma_info || !uma_info->num_entries)
+		return -ENODEV;
+
+	for (int i = 0; i < uma_info->num_entries; i++) {
+		memory_carved = uma_info->entries[i].memory_carved_mb;
+		if (memory_carved >= SZ_1G/SZ_1M) {
+			size += sysfs_emit_at(buf, size, "%d: %s (%u GB)\n",
+					      i,
+					      uma_info->entries[i].name,
+					      memory_carved >> 10);
+		} else {
+			size += sysfs_emit_at(buf, size, "%d: %s (%u MB)\n",
+					      i,
+					      uma_info->entries[i].name,
+					      memory_carved);
+		}
+	}
+
+	return size;
+}
+static DEVICE_ATTR_RO(carveout_options);
+
+static ssize_t carveout_show(struct device *dev,
+			     struct device_attribute *attr,
+			     char *buf)
+{
+	return sysfs_emit(buf, "%u\n", amdgpu_acpi_priv.atcs.uma_info.uma_option_index);
+}
+
+static ssize_t carveout_store(struct device *dev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
+	struct drm_device *ddev = dev_get_drvdata(dev);
+	struct amdgpu_device *adev = drm_to_adev(ddev);
+	struct amdgpu_uma_carveout_option *opt;
+	unsigned long val;
+	uint8_t flags;
+	int r;
+
+	r = kstrtoul(buf, 10, &val);
+	if (r)
+		return r;
+
+	if (val >= uma_info->num_entries)
+		return -EINVAL;
+
+	val = array_index_nospec(val, uma_info->num_entries);
+	opt = &uma_info->entries[val];
+
+	if (!(opt->flags & AMDGPU_UMA_FLAG_AUTO) &&
+	    !(opt->flags & AMDGPU_UMA_FLAG_CUSTOM)) {
+		drm_err_once(ddev, "Option %lu not supported due to lack of Custom/Auto flag", val);
+		return -EINVAL;
+	}
+
+	flags = opt->flags;
+	flags &= ~((flags & AMDGPU_UMA_FLAG_AUTO) >> 1);
+
+	guard(mutex)(&uma_info->update_lock);
+
+	r = amdgpu_acpi_set_uma_allocation_size(adev, val, flags);
+	if (r)
+		return r;
+
+	uma_info->uma_option_index = val;
+
+	return count;
+}
+static DEVICE_ATTR_RW(carveout);
+
+static struct attribute *amdgpu_uma_attrs[] = {
+	&dev_attr_carveout.attr,
+	&dev_attr_carveout_options.attr,
+	NULL
+};
+
+const struct attribute_group amdgpu_uma_attr_group = {
+	.name = "uma",
+	.attrs = amdgpu_uma_attrs
+};
+
+static int amdgpu_acpi_uma_option_init(struct amdgpu_device *adev)
+{
+	struct amdgpu_atcs *atcs = &amdgpu_acpi_priv.atcs;
+	int rc;
+
+	if (!atcs->functions.set_uma_allocation_size)
+		return -ENODEV;
+
+	rc = amdgpu_atomfirmware_get_uma_carveout_info(adev, &atcs->uma_info);
+	if (rc) {
+		drm_dbg(adev_to_drm(adev),
+			"Failed to parse UMA carveout info from VBIOS: %d\n", rc);
+		goto out_info;
+	}
+
+	mutex_init(&atcs->uma_info.update_lock);
+
+	rc = devm_device_add_group(adev->dev, &amdgpu_uma_attr_group);
+	if (rc) {
+		drm_dbg(adev_to_drm(adev), "Failed to add UMA carveout sysfs interfaces %d\n", rc);
+		goto out_attr;
+	}
+
+	return 0;
+
+out_attr:
+	mutex_destroy(&atcs->uma_info.update_lock);
+out_info:
+	return rc;
+}
+
+static void amdgpu_acpi_uma_option_fini(void)
+{
+	struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
+
+	mutex_destroy(&uma_info->update_lock);
+	uma_info->num_entries = 0;
+}
+
 /**
  * amdgpu_acpi_event - handle notify events
  *
@@ -1290,6 +1422,12 @@ static int amdgpu_acpi_event(struct notifier_block *nb,
 int amdgpu_acpi_init(struct amdgpu_device *adev)
 {
 	struct amdgpu_atif *atif = &amdgpu_acpi_priv.atif;
+	int rc;
+
+	rc = amdgpu_acpi_uma_option_init(adev);
+
+	if (rc)
+		drm_dbg(adev_to_drm(adev), "Not creating uma carveout interfaces: %d", rc);
 
 	if (atif->notifications.brightness_change) {
 		if (adev->dc_enabled) {
@@ -1342,6 +1480,7 @@ void amdgpu_acpi_get_backlight_caps(struct amdgpu_dm_backlight_caps *caps)
 void amdgpu_acpi_fini(struct amdgpu_device *adev)
 {
 	unregister_acpi_notifier(&adev->acpi_nb);
+	amdgpu_acpi_uma_option_fini();
 }
 
 /**

-- 
2.43.0

On Mon, Dec 1, 2025 at 6:09 AM Yo-Jung Leo Lin (AMD) <Leo.Lin@amd.com> wrote:
>
> Add a uma/ directory containing two sysfs files as interfaces to
> inspect or change UMA carveout size. These files are:
>
> - uma/carveout_options: a read-only file listing all the available
>   UMA allocation options and their index.
>
> - uma/carveout: a file that is both readable and writable. On read,
>   it shows the index of the current setting. Writing a valid index
>   into this file allows users to change the UMA carveout size to that
>   option on the next boot.
>
> Co-developed-by: Mario Limonciello (AMD) <superm1@kernel.org>
> Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
> Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@amd.com>

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 139 +++++++++++++++++++++++++++++++
>  1 file changed, 139 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> index bce9027fa241..2c0405cdc436 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> @@ -30,6 +30,8 @@
>  #include <linux/power_supply.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/suspend.h>
> +#include <linux/device.h>
> +#include <linux/nospec.h>
>  #include <acpi/video.h>
>  #include <acpi/actbl.h>
>
> @@ -1246,6 +1248,136 @@ int amdgpu_acpi_get_mem_info(struct amdgpu_device *adev, int xcc_id,
>         return -ENOENT;
>  }
>
> +static ssize_t carveout_options_show(struct device *dev,
> +                                    struct device_attribute *attr,
> +                                    char *buf)
> +{
> +       struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
> +       uint32_t memory_carved;
> +       ssize_t size = 0;
> +
> +       if (!uma_info || !uma_info->num_entries)
> +               return -ENODEV;
> +
> +       for (int i = 0; i < uma_info->num_entries; i++) {
> +               memory_carved = uma_info->entries[i].memory_carved_mb;
> +               if (memory_carved >= SZ_1G/SZ_1M) {
> +                       size += sysfs_emit_at(buf, size, "%d: %s (%u GB)\n",
> +                                             i,
> +                                             uma_info->entries[i].name,
> +                                             memory_carved >> 10);
> +               } else {
> +                       size += sysfs_emit_at(buf, size, "%d: %s (%u MB)\n",
> +                                             i,
> +                                             uma_info->entries[i].name,
> +                                             memory_carved);
> +               }
> +       }
> +
> +       return size;
> +}
> +static DEVICE_ATTR_RO(carveout_options);
> +
> +static ssize_t carveout_show(struct device *dev,
> +                            struct device_attribute *attr,
> +                            char *buf)
> +{
> +       return sysfs_emit(buf, "%u\n", amdgpu_acpi_priv.atcs.uma_info.uma_option_index);
> +}
> +
> +static ssize_t carveout_store(struct device *dev,
> +                             struct device_attribute *attr,
> +                             const char *buf, size_t count)
> +{
> +       struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
> +       struct drm_device *ddev = dev_get_drvdata(dev);
> +       struct amdgpu_device *adev = drm_to_adev(ddev);
> +       struct amdgpu_uma_carveout_option *opt;
> +       unsigned long val;
> +       uint8_t flags;
> +       int r;
> +
> +       r = kstrtoul(buf, 10, &val);
> +       if (r)
> +               return r;
> +
> +       if (val >= uma_info->num_entries)
> +               return -EINVAL;
> +
> +       val = array_index_nospec(val, uma_info->num_entries);
> +       opt = &uma_info->entries[val];
> +
> +       if (!(opt->flags & AMDGPU_UMA_FLAG_AUTO) &&
> +           !(opt->flags & AMDGPU_UMA_FLAG_CUSTOM)) {
> +               drm_err_once(ddev, "Option %lu not supported due to lack of Custom/Auto flag", val);
> +               return -EINVAL;
> +       }
> +
> +       flags = opt->flags;
> +       flags &= ~((flags & AMDGPU_UMA_FLAG_AUTO) >> 1);
> +
> +       guard(mutex)(&uma_info->update_lock);
> +
> +       r = amdgpu_acpi_set_uma_allocation_size(adev, val, flags);
> +       if (r)
> +               return r;
> +
> +       uma_info->uma_option_index = val;
> +
> +       return count;
> +}
> +static DEVICE_ATTR_RW(carveout);
> +
> +static struct attribute *amdgpu_uma_attrs[] = {
> +       &dev_attr_carveout.attr,
> +       &dev_attr_carveout_options.attr,
> +       NULL
> +};
> +
> +const struct attribute_group amdgpu_uma_attr_group = {
> +       .name = "uma",
> +       .attrs = amdgpu_uma_attrs
> +};
> +
> +static int amdgpu_acpi_uma_option_init(struct amdgpu_device *adev)
> +{
> +       struct amdgpu_atcs *atcs = &amdgpu_acpi_priv.atcs;
> +       int rc;
> +
> +       if (!atcs->functions.set_uma_allocation_size)
> +               return -ENODEV;
> +
> +       rc = amdgpu_atomfirmware_get_uma_carveout_info(adev, &atcs->uma_info);
> +       if (rc) {
> +               drm_dbg(adev_to_drm(adev),
> +                       "Failed to parse UMA carveout info from VBIOS: %d\n", rc);
> +               goto out_info;
> +       }
> +
> +       mutex_init(&atcs->uma_info.update_lock);
> +
> +       rc = devm_device_add_group(adev->dev, &amdgpu_uma_attr_group);
> +       if (rc) {
> +               drm_dbg(adev_to_drm(adev), "Failed to add UMA carveout sysfs interfaces %d\n", rc);
> +               goto out_attr;
> +       }
> +
> +       return 0;
> +
> +out_attr:
> +       mutex_destroy(&atcs->uma_info.update_lock);
> +out_info:
> +       return rc;
> +}
> +
> +static void amdgpu_acpi_uma_option_fini(void)
> +{
> +       struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
> +
> +       mutex_destroy(&uma_info->update_lock);
> +       uma_info->num_entries = 0;
> +}
> +
>  /**
>   * amdgpu_acpi_event - handle notify events
>   *
> @@ -1290,6 +1422,12 @@ static int amdgpu_acpi_event(struct notifier_block *nb,
>  int amdgpu_acpi_init(struct amdgpu_device *adev)
>  {
>         struct amdgpu_atif *atif = &amdgpu_acpi_priv.atif;
> +       int rc;
> +
> +       rc = amdgpu_acpi_uma_option_init(adev);
> +
> +       if (rc)
> +               drm_dbg(adev_to_drm(adev), "Not creating uma carveout interfaces: %d", rc);
>
>         if (atif->notifications.brightness_change) {
>                 if (adev->dc_enabled) {
> @@ -1342,6 +1480,7 @@ void amdgpu_acpi_get_backlight_caps(struct amdgpu_dm_backlight_caps *caps)
>  void amdgpu_acpi_fini(struct amdgpu_device *adev)
>  {
>         unregister_acpi_notifier(&adev->acpi_nb);
> +       amdgpu_acpi_uma_option_fini();
>  }
>
>  /**
>
> --
> 2.43.0
>