From: Mario Limonciello <mario.limonciello@amd.com>

SMN access was bolted into amd_nb mostly as convenience.  This has
limitations though that require incurring tech debt to keep it working.

Move SMN access to its own driver.

[Yazen: Adjust commit message and add MAINTAINERS entry]

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
---
 MAINTAINERS                          |   8 +++
 arch/x86/Kconfig                     |   3 +
 arch/x86/include/asm/amd_nb.h        |   3 -
 arch/x86/include/asm/amd_smn.h       |  11 +++
 arch/x86/kernel/Makefile             |   1 +
 arch/x86/kernel/amd_nb.c             |  89 -----------------------
 arch/x86/kernel/amd_smn.c            | 101 +++++++++++++++++++++++++++
 arch/x86/pci/fixup.c                 |   4 +-
 drivers/edac/Kconfig                 |   1 +
 drivers/edac/amd64_edac.c            |   1 +
 drivers/hwmon/Kconfig                |   2 +-
 drivers/hwmon/k10temp.c              |   2 +-
 drivers/platform/x86/amd/pmc/Kconfig |   2 +-
 drivers/platform/x86/amd/pmc/pmc.c   |   2 +-
 drivers/platform/x86/amd/pmf/Kconfig |   2 +-
 drivers/platform/x86/amd/pmf/core.c  |   2 +-
 drivers/ras/amd/atl/Kconfig          |   1 +
 drivers/ras/amd/atl/internal.h       |   1 +
 18 files changed, 136 insertions(+), 100 deletions(-)
 create mode 100644 arch/x86/include/asm/amd_smn.h
 create mode 100644 arch/x86/kernel/amd_smn.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 9ca246aef7ab..cb9af4353b31 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1180,6 +1180,14 @@ S:	Maintained
 F:	Documentation/hid/amd-sfh*
 F:	drivers/hid/amd-sfh-hid/
 
+AMD SMN DRIVER
+M:	Mario Limonciello <mario.limonciello@amd.com>
+M:	Yazen Ghannam <yazen.ghannam@amd.com>
+L:	linux-kernel@vger.kernel.org
+S:	Supported
+F:	arch/x86/include/asm/amd_smn.h
+F:	arch/x86/kernel/amd_smn.c
+
 AMD SPI DRIVER
 M:	Sanjay R Mehta <sanju.mehta@amd.com>
 S:	Maintained
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ba5252d8e21c..a03ffa5b6bb1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -3128,6 +3128,9 @@ config AMD_NODE
 	def_bool y
 	depends on CPU_SUP_AMD && PCI
 
+config AMD_SMN
+	def_bool y
+	depends on AMD_NODE
 endmenu
 
 menu "Binary Emulations"
diff --git a/arch/x86/include/asm/amd_nb.h b/arch/x86/include/asm/amd_nb.h
index b3b42e585655..55c03d3495bc 100644
--- a/arch/x86/include/asm/amd_nb.h
+++ b/arch/x86/include/asm/amd_nb.h
@@ -21,9 +21,6 @@ extern int amd_numa_init(void);
 extern int amd_get_subcaches(int);
 extern int amd_set_subcaches(int, unsigned long);
 
-int __must_check amd_smn_read(u16 node, u32 address, u32 *value);
-int __must_check amd_smn_write(u16 node, u32 address, u32 value);
-
 struct amd_l3_cache {
 	unsigned indices;
 	u8	 subcaches[4];
diff --git a/arch/x86/include/asm/amd_smn.h b/arch/x86/include/asm/amd_smn.h
new file mode 100644
index 000000000000..6850de69f863
--- /dev/null
+++ b/arch/x86/include/asm/amd_smn.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_AMD_SMN_H
+#define _ASM_X86_AMD_SMN_H
+
+#include <linux/types.h>
+#include <asm/amd_node.h>
+
+int __must_check amd_smn_read(u16 node, u32 address, u32 *value);
+int __must_check amd_smn_write(u16 node, u32 address, u32 value);
+
+#endif /* _ASM_X86_AMD_SMN_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index b43eb7e384eb..1df22821f72d 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -120,6 +120,7 @@ obj-$(CONFIG_HPET_TIMER) 	+= hpet.o
 
 obj-$(CONFIG_AMD_NB)		+= amd_nb.o
 obj-$(CONFIG_AMD_NODE)		+= amd_node.o
+obj-$(CONFIG_AMD_SMN)		+= amd_smn.o
 obj-$(CONFIG_DEBUG_NMI_SELFTEST) += nmi_selftest.o
 
 obj-$(CONFIG_KVM_GUEST)		+= kvm.o kvmclock.o
diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index 9b159f9b4a11..10cdeddeda02 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -15,9 +15,6 @@
 #include <linux/pci_ids.h>
 #include <asm/amd_nb.h>
 
-/* Protect the PCI config register pairs used for SMN. */
-static DEFINE_MUTEX(smn_mutex);
-
 static u32 *flush_words;
 
 static const struct pci_device_id amd_nb_misc_ids[] = {
@@ -59,92 +56,6 @@ struct amd_northbridge *node_to_amd_nb(int node)
 }
 EXPORT_SYMBOL_GPL(node_to_amd_nb);
 
-/*
- * SMN accesses may fail in ways that are difficult to detect here in the called
- * functions amd_smn_read() and amd_smn_write(). Therefore, callers must do
- * their own checking based on what behavior they expect.
- *
- * For SMN reads, the returned value may be zero if the register is Read-as-Zero.
- * Or it may be a "PCI Error Response", e.g. all 0xFFs. The "PCI Error Response"
- * can be checked here, and a proper error code can be returned.
- *
- * But the Read-as-Zero response cannot be verified here. A value of 0 may be
- * correct in some cases, so callers must check that this correct is for the
- * register/fields they need.
- *
- * For SMN writes, success can be determined through a "write and read back"
- * However, this is not robust when done here.
- *
- * Possible issues:
- *
- * 1) Bits that are "Write-1-to-Clear". In this case, the read value should
- *    *not* match the write value.
- *
- * 2) Bits that are "Read-as-Zero"/"Writes-Ignored". This information cannot be
- *    known here.
- *
- * 3) Bits that are "Reserved / Set to 1". Ditto above.
- *
- * Callers of amd_smn_write() should do the "write and read back" check
- * themselves, if needed.
- *
- * For #1, they can see if their target bits got cleared.
- *
- * For #2 and #3, they can check if their target bits got set as intended.
- *
- * This matches what is done for RDMSR/WRMSR. As long as there's no #GP, then
- * the operation is considered a success, and the caller does their own
- * checking.
- */
-static int __amd_smn_rw(u16 node, u32 address, u32 *value, bool write)
-{
-	struct pci_dev *root;
-	int err = -ENODEV;
-
-	if (node >= amd_northbridges.num)
-		goto out;
-
-	root = node_to_amd_nb(node)->root;
-	if (!root)
-		goto out;
-
-	mutex_lock(&smn_mutex);
-
-	err = pci_write_config_dword(root, 0x60, address);
-	if (err) {
-		pr_warn("Error programming SMN address 0x%x.\n", address);
-		goto out_unlock;
-	}
-
-	err = (write ? pci_write_config_dword(root, 0x64, *value)
-		     : pci_read_config_dword(root, 0x64, value));
-
-out_unlock:
-	mutex_unlock(&smn_mutex);
-
-out:
-	return err;
-}
-
-int __must_check amd_smn_read(u16 node, u32 address, u32 *value)
-{
-	int err = __amd_smn_rw(node, address, value, false);
-
-	if (PCI_POSSIBLE_ERROR(*value)) {
-		err = -ENODEV;
-		*value = 0;
-	}
-
-	return err;
-}
-EXPORT_SYMBOL_GPL(amd_smn_read);
-
-int __must_check amd_smn_write(u16 node, u32 address, u32 value)
-{
-	return __amd_smn_rw(node, address, &value, true);
-}
-EXPORT_SYMBOL_GPL(amd_smn_write);
-
 static int amd_cache_northbridges(void)
 {
 	struct amd_northbridge *nb;
diff --git a/arch/x86/kernel/amd_smn.c b/arch/x86/kernel/amd_smn.c
new file mode 100644
index 000000000000..06160a9e2444
--- /dev/null
+++ b/arch/x86/kernel/amd_smn.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD SMN driver, used for register access
+ * Copyright 2024 Advanced Micro Devices, Inc.
+ */
+
+#define pr_fmt(fmt) "amd_smn: " fmt
+
+#include <linux/pci.h>
+
+#include <asm/amd_nb.h>
+#include <asm/amd_smn.h>
+
+/* Protect the PCI config register pairs used for SMN. */
+static DEFINE_MUTEX(smn_mutex);
+
+/*
+ * SMN accesses may fail in ways that are difficult to detect here in the called
+ * functions amd_smn_read() and amd_smn_write(). Therefore, callers must do
+ * their own checking based on what behavior they expect.
+ *
+ * For SMN reads, the returned value may be zero if the register is Read-as-Zero.
+ * Or it may be a "PCI Error Response", e.g. all 0xFFs. The "PCI Error Response"
+ * can be checked here, and a proper error code can be returned.
+ *
+ * But the Read-as-Zero response cannot be verified here. A value of 0 may be
+ * correct in some cases, so callers must check that this correct is for the
+ * register/fields they need.
+ *
+ * For SMN writes, success can be determined through a "write and read back"
+ * However, this is not robust when done here.
+ *
+ * Possible issues:
+ *
+ * 1) Bits that are "Write-1-to-Clear". In this case, the read value should
+ *    *not* match the write value.
+ *
+ * 2) Bits that are "Read-as-Zero"/"Writes-Ignored". This information cannot be
+ *    known here.
+ *
+ * 3) Bits that are "Reserved / Set to 1". Ditto above.
+ *
+ * Callers of amd_smn_write() should do the "write and read back" check
+ * themselves, if needed.
+ *
+ * For #1, they can see if their target bits got cleared.
+ *
+ * For #2 and #3, they can check if their target bits got set as intended.
+ *
+ * This matches what is done for RDMSR/WRMSR. As long as there's no #GP, then
+ * the operation is considered a success, and the caller does their own
+ * checking.
+ */
+static int __amd_smn_rw(u16 node, u32 address, u32 *value, bool write)
+{
+	struct pci_dev *root;
+	int err = -ENODEV;
+
+	if (node >= amd_nb_num())
+		goto out;
+
+	root = node_to_amd_nb(node)->root;
+	if (!root)
+		goto out;
+
+	mutex_lock(&smn_mutex);
+
+	err = pci_write_config_dword(root, 0x60, address);
+	if (err) {
+		pr_warn("Error programming SMN address 0x%x.\n", address);
+		goto out_unlock;
+	}
+
+	err = (write ? pci_write_config_dword(root, 0x64, *value)
+		     : pci_read_config_dword(root, 0x64, value));
+
+out_unlock:
+	mutex_unlock(&smn_mutex);
+
+out:
+	return err;
+}
+
+int __must_check amd_smn_read(u16 node, u32 address, u32 *value)
+{
+	int err = __amd_smn_rw(node, address, value, false);
+
+	if (PCI_POSSIBLE_ERROR(*value)) {
+		err = -ENODEV;
+		*value = 0;
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(amd_smn_read);
+
+int __must_check amd_smn_write(u16 node, u32 address, u32 value)
+{
+	return __amd_smn_rw(node, address, &value, true);
+}
+EXPORT_SYMBOL_GPL(amd_smn_write);
diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c
index 98a9bb92d75c..e8ea627c22b4 100644
--- a/arch/x86/pci/fixup.c
+++ b/arch/x86/pci/fixup.c
@@ -9,7 +9,7 @@
 #include <linux/pci.h>
 #include <linux/suspend.h>
 #include <linux/vgaarb.h>
-#include <asm/amd_nb.h>
+#include <asm/amd_smn.h>
 #include <asm/hpet.h>
 #include <asm/pci_x86.h>
 
@@ -828,7 +828,7 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x7910, rs690_fix_64bit_dma);
 
 #endif
 
-#ifdef CONFIG_AMD_NB
+#ifdef CONFIG_AMD_SMN
 
 #define AMD_15B8_RCC_DEV2_EPF0_STRAP2                                  0x10136008
 #define AMD_15B8_RCC_DEV2_EPF0_STRAP2_NO_SOFT_RESET_DEV2_F0_MASK       0x00000080L
diff --git a/drivers/edac/Kconfig b/drivers/edac/Kconfig
index 81af6c344d6b..acdd920b8769 100644
--- a/drivers/edac/Kconfig
+++ b/drivers/edac/Kconfig
@@ -78,6 +78,7 @@ config EDAC_GHES
 config EDAC_AMD64
 	tristate "AMD64 (Opteron, Athlon64)"
 	depends on AMD_NB && EDAC_DECODE_MCE
+	depends on AMD_SMN
 	imply AMD_ATL
 	help
 	  Support for error detection and correction of DRAM ECC errors on
diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
index ddfbdb66b794..b0ee0593137b 100644
--- a/drivers/edac/amd64_edac.c
+++ b/drivers/edac/amd64_edac.c
@@ -2,6 +2,7 @@
 #include <linux/ras.h>
 #include "amd64_edac.h"
 #include <asm/amd_nb.h>
+#include <asm/amd_smn.h>
 
 static struct edac_pci_ctl_info *pci_ctl;
 
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 08a3c863f80a..bf2bd7098f2c 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -324,7 +324,7 @@ config SENSORS_K8TEMP
 
 config SENSORS_K10TEMP
 	tristate "AMD Family 10h+ temperature sensor"
-	depends on X86 && PCI && AMD_NB
+	depends on X86 && PCI && AMD_SMN
 	help
 	  If you say yes here you get support for the temperature
 	  sensor(s) inside your CPU. Supported are later revisions of
diff --git a/drivers/hwmon/k10temp.c b/drivers/hwmon/k10temp.c
index 7dc19c5d62ac..1a16640d2fa1 100644
--- a/drivers/hwmon/k10temp.c
+++ b/drivers/hwmon/k10temp.c
@@ -20,7 +20,7 @@
 #include <linux/module.h>
 #include <linux/pci.h>
 #include <linux/pci_ids.h>
-#include <asm/amd_nb.h>
+#include <asm/amd_smn.h>
 #include <asm/processor.h>
 
 MODULE_DESCRIPTION("AMD Family 10h+ CPU core temperature monitor");
diff --git a/drivers/platform/x86/amd/pmc/Kconfig b/drivers/platform/x86/amd/pmc/Kconfig
index 94f9563d8be7..d9cae227aff9 100644
--- a/drivers/platform/x86/amd/pmc/Kconfig
+++ b/drivers/platform/x86/amd/pmc/Kconfig
@@ -5,7 +5,7 @@
 
 config AMD_PMC
 	tristate "AMD SoC PMC driver"
-	depends on ACPI && PCI && RTC_CLASS && AMD_NB
+	depends on ACPI && PCI && RTC_CLASS && AMD_SMN
 	depends on SUSPEND
 	select SERIO
 	help
diff --git a/drivers/platform/x86/amd/pmc/pmc.c b/drivers/platform/x86/amd/pmc/pmc.c
index bbb8edb62e00..663cf8d671c7 100644
--- a/drivers/platform/x86/amd/pmc/pmc.c
+++ b/drivers/platform/x86/amd/pmc/pmc.c
@@ -10,7 +10,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
-#include <asm/amd_nb.h>
+#include <asm/amd_smn.h>
 #include <linux/acpi.h>
 #include <linux/bitfield.h>
 #include <linux/bits.h>
diff --git a/drivers/platform/x86/amd/pmf/Kconfig b/drivers/platform/x86/amd/pmf/Kconfig
index f4fa8bd8bda8..67913f64faf3 100644
--- a/drivers/platform/x86/amd/pmf/Kconfig
+++ b/drivers/platform/x86/amd/pmf/Kconfig
@@ -7,7 +7,7 @@ config AMD_PMF
 	tristate "AMD Platform Management Framework"
 	depends on ACPI && PCI
 	depends on POWER_SUPPLY
-	depends on AMD_NB
+	depends on AMD_SMN
 	select ACPI_PLATFORM_PROFILE
 	depends on TEE && AMDTEE
 	depends on AMD_SFH_HID
diff --git a/drivers/platform/x86/amd/pmf/core.c b/drivers/platform/x86/amd/pmf/core.c
index d6af0ca036f1..21f9ec19941b 100644
--- a/drivers/platform/x86/amd/pmf/core.c
+++ b/drivers/platform/x86/amd/pmf/core.c
@@ -8,7 +8,7 @@
  * Author: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
  */
 
-#include <asm/amd_nb.h>
+#include <asm/amd_smn.h>
 #include <linux/debugfs.h>
 #include <linux/iopoll.h>
 #include <linux/module.h>
diff --git a/drivers/ras/amd/atl/Kconfig b/drivers/ras/amd/atl/Kconfig
index 551680073e43..819ac593e743 100644
--- a/drivers/ras/amd/atl/Kconfig
+++ b/drivers/ras/amd/atl/Kconfig
@@ -10,6 +10,7 @@
 config AMD_ATL
 	tristate "AMD Address Translation Library"
 	depends on AMD_NB && X86_64 && RAS
+	depends on AMD_SMN
 	depends on MEMORY_FAILURE
 	default N
 	help
diff --git a/drivers/ras/amd/atl/internal.h b/drivers/ras/amd/atl/internal.h
index 143d04c779a8..49cd3e95e0c6 100644
--- a/drivers/ras/amd/atl/internal.h
+++ b/drivers/ras/amd/atl/internal.h
@@ -18,6 +18,7 @@
 #include <linux/ras.h>
 
 #include <asm/amd_nb.h>
+#include <asm/amd_smn.h>
 
 #include "reg_fields.h"
 
-- 
2.43.0

On Wed, Oct 23, 2024 at 05:21:44PM +0000, Yazen Ghannam wrote:
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index ba5252d8e21c..a03ffa5b6bb1 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -3128,6 +3128,9 @@ config AMD_NODE
>  	def_bool y
>  	depends on CPU_SUP_AMD && PCI
>  
> +config AMD_SMN
> +	def_bool y
> +	depends on AMD_NODE

Why is this a separate compilation unit and not part of amd_node.c? Especially
if it depends on it.

I don't see the real need for having smaller compilation units. Both the node
and the smn stuff will end up being built-in in 99% of the configs. So why are
we making separate Kconfig items and yadda yadda?

Just do a single amd_node and that's it. We can always split later, if really
needed.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

On Mon, Nov 04, 2024 at 03:29:58PM +0100, Borislav Petkov wrote:
> On Wed, Oct 23, 2024 at 05:21:44PM +0000, Yazen Ghannam wrote:
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index ba5252d8e21c..a03ffa5b6bb1 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -3128,6 +3128,9 @@ config AMD_NODE
> >  	def_bool y
> >  	depends on CPU_SUP_AMD && PCI
> >  
> > +config AMD_SMN
> > +	def_bool y
> > +	depends on AMD_NODE
> 
> Why is this a separate compilation unit and not part of amd_node.c? Especially
> if it depends on it.
> 
> I don't see the real need for having smaller compilation units. Both the node
> and the smn stuff will end up being built-in in 99% of the configs. So why are
> we making separate Kconfig items and yadda yadda?
> 

AMD_NB (legacy systems) and AMD_SMN (Zen-based systems) would both
depend on AMD_NODE. The thinking is that a user could build a minimal
config for either legacy or Zen-based systems.

> Just do a single amd_node and that's it. We can always split later, if really
> needed.
>

Okay, will do.

Thanks,
Yazen

On Tue, Nov 05, 2024 at 09:58:26AM -0500, Yazen Ghannam wrote:
> AMD_NB (legacy systems)

That's legacy and won't get anything new.

> and AMD_SMN (Zen-based systems) would both depend on AMD_NODE. The thinking
> is that a user could build a minimal config for either legacy or Zen-based
> systems.

amd_node is three functions.

amd_node_get_func() can go into a header so that both nb.c and node.c can call
it and smn.c and node.c can be a single compilation unit.

> > Just do a single amd_node and that's it. We can always split later, if really
> > needed.
> >
> 
> Okay, will do.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette