platform/x86/amd: pmc: Add sysfs files for SMU

The CPU/APU SMU FW version and program is currently discoverable by
turning on dynamic debugging or examining debugfs for the amdgpu
driver. To make this more discoverable, create a dedicated sysfs
file for it that userspace can parse without debugging enabled.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20220914141850.259-1-mario.limonciello@amd.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Documentation/ABI/testing/sysfs-amd-pmc

@@ -0,0 +1,13 @@
+What:		/sys/bus/platform/drivers/amd_pmc/*/smu_fw_version
+Date:		October 2022
+Contact:	Mario Limonciello <mario.limonciello@amd.com>
+Description:	Reading this file reports the version of the firmware loaded to
+		System Management Unit (SMU) contained in AMD CPUs and
+		APUs.
+
+What:		/sys/bus/platform/drivers/amd_pmc/*/smu_program
+Date:		October 2022
+Contact:	Mario Limonciello <mario.limonciello@amd.com>
+Description:	Reading this file reports the program corresponding to the SMU
+		firmware version.  The program field is used to disambiguate two
+		APU/CPU models that can share the same firmware binary.

drivers/platform/x86/amd/pmc.c

@@ -457,6 +457,44 @@ static int amd_pmc_get_smu_version(struct amd_pmc_dev *dev)
 	return 0;
 }
 
+static ssize_t smu_fw_version_show(struct device *d, struct device_attribute *attr,
+				   char *buf)
+{
+	struct amd_pmc_dev *dev = dev_get_drvdata(d);
+
+	if (!dev->major) {
+		int rc = amd_pmc_get_smu_version(dev);
+
+		if (rc)
+			return rc;
+	}
+	return sysfs_emit(buf, "%u.%u.%u\n", dev->major, dev->minor, dev->rev);
+}
+
+static ssize_t smu_program_show(struct device *d, struct device_attribute *attr,
+				   char *buf)
+{
+	struct amd_pmc_dev *dev = dev_get_drvdata(d);
+
+	if (!dev->major) {
+		int rc = amd_pmc_get_smu_version(dev);
+
+		if (rc)
+			return rc;
+	}
+	return sysfs_emit(buf, "%u\n", dev->smu_program);
+}
+
+static DEVICE_ATTR_RO(smu_fw_version);
+static DEVICE_ATTR_RO(smu_program);
+
+static struct attribute *pmc_attrs[] = {
+	&dev_attr_smu_fw_version.attr,
+	&dev_attr_smu_program.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(pmc);
+
 static int amd_pmc_idlemask_show(struct seq_file *s, void *unused)
 {
 	struct amd_pmc_dev *dev = s->private;
@@ -943,6 +981,7 @@ static struct platform_driver amd_pmc_driver = {
 	.driver = {
 		.name = "amd_pmc",
 		.acpi_match_table = amd_pmc_acpi_ids,
+		.dev_groups = pmc_groups,
 	},
 	.probe = amd_pmc_probe,
 	.remove = amd_pmc_remove,