cpufreq: amd-pstate: Add a kernel config option to set default mode

Users are having more success with amd-pstate since the introduction
of EPP and Guided modes.  To expose the driver to more users by default
introduce a kernel configuration option for setting the default mode.

Users can use an integer to map out which default mode they want to use
in lieu of a kernel command line option.

This will default to EPP, but only if:
 1) The CPU supports an MSR.
 2) The system profile is identified
 3) The system profile is identified as a non-server by the FADT.

Link: https://gitlab.freedesktop.org/hadess/power-profiles-daemon/-/merge_requests/121
Acked-by: Huang Rui <[email protected]>
Reviewed-by: Gautham R. Shenoy <[email protected]>
Co-developed-by: Perry Yuan <[email protected]>
Signed-off-by: Perry Yuan <[email protected]>
Signed-off-by: Mario Limonciello <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: superm1

drivers/cpufreq/Kconfig.x86

@@ -51,6 +51,23 @@ config X86_AMD_PSTATE
 
 	  If in doubt, say N.
 
+config X86_AMD_PSTATE_DEFAULT_MODE
+	int "AMD Processor P-State default mode"
+	depends on X86_AMD_PSTATE
+	default 3 if X86_AMD_PSTATE
+	range 1 4
+	help
+	  Select the default mode the amd-pstate driver will use on
+	  supported hardware.
+	  The value set has the following meanings:
+		1 -> Disabled
+		2 -> Passive
+		3 -> Active (EPP)
+		4 -> Guided
+
+	  For details, take a look at:
+	  <file:Documentation/admin-guide/pm/amd-pstate.rst>.
+
 config X86_AMD_PSTATE_UT
 	tristate "selftest for AMD Processor P-State driver"
 	depends on X86 && ACPI_PROCESSOR

drivers/cpufreq/amd-pstate.c

@@ -62,7 +62,7 @@
 static struct cpufreq_driver *current_pstate_driver;
 static struct cpufreq_driver amd_pstate_driver;
 static struct cpufreq_driver amd_pstate_epp_driver;
-static int cppc_state = AMD_PSTATE_DISABLE;
+static int cppc_state = AMD_PSTATE_UNDEFINED;
 static bool cppc_enabled;
 
 /*
@@ -1410,22 +1410,32 @@ static struct cpufreq_driver amd_pstate_epp_driver = {
 	.attr		= amd_pstate_epp_attr,
 };
 
+static int __init amd_pstate_set_driver(int mode_idx)
+{
+	if (mode_idx >= AMD_PSTATE_DISABLE && mode_idx < AMD_PSTATE_MAX) {
+		cppc_state = mode_idx;
+		if (cppc_state == AMD_PSTATE_DISABLE)
+			pr_info("driver is explicitly disabled\n");
+
+		if (cppc_state == AMD_PSTATE_ACTIVE)
+			current_pstate_driver = &amd_pstate_epp_driver;
+
+		if (cppc_state == AMD_PSTATE_PASSIVE || cppc_state == AMD_PSTATE_GUIDED)
+			current_pstate_driver = &amd_pstate_driver;
+
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
 static int __init amd_pstate_init(void)
 {
 	struct device *dev_root;
 	int ret;
 
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
 		return -ENODEV;
-	/*
-	 * by default the pstate driver is disabled to load
-	 * enable the amd_pstate passive mode driver explicitly
-	 * with amd_pstate=passive or other modes in kernel command line
-	 */
-	if (cppc_state == AMD_PSTATE_DISABLE) {
-		pr_info("driver load is disabled, boot with specific mode to enable this\n");
-		return -ENODEV;
-	}
 
 	if (!acpi_cpc_valid()) {
 		pr_warn_once("the _CPC object is not present in SBIOS or ACPI disabled\n");
@@ -1436,6 +1446,33 @@ static int __init amd_pstate_init(void)
 	if (cpufreq_get_current_driver())
 		return -EEXIST;
 
+	switch (cppc_state) {
+	case AMD_PSTATE_UNDEFINED:
+		/* Disable on the following configs by default:
+		 * 1. Undefined platforms
+		 * 2. Server platforms
+		 * 3. Shared memory designs
+		 */
+		if (amd_pstate_acpi_pm_profile_undefined() ||
+		    amd_pstate_acpi_pm_profile_server() ||
+		    !boot_cpu_has(X86_FEATURE_CPPC)) {
+			pr_info("driver load is disabled, boot with specific mode to enable this\n");
+			return -ENODEV;
+		}
+		ret = amd_pstate_set_driver(CONFIG_X86_AMD_PSTATE_DEFAULT_MODE);
+		if (ret)
+			return ret;
+		break;
+	case AMD_PSTATE_DISABLE:
+		return -ENODEV;
+	case AMD_PSTATE_PASSIVE:
+	case AMD_PSTATE_ACTIVE:
+	case AMD_PSTATE_GUIDED:
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	/* capability check */
 	if (boot_cpu_has(X86_FEATURE_CPPC)) {
 		pr_debug("AMD CPPC MSR based functionality is supported\n");
@@ -1488,21 +1525,7 @@ static int __init amd_pstate_param(char *str)
 	size = strlen(str);
 	mode_idx = get_mode_idx_from_str(str, size);
 
-	if (mode_idx >= AMD_PSTATE_DISABLE && mode_idx < AMD_PSTATE_MAX) {
-		cppc_state = mode_idx;
-		if (cppc_state == AMD_PSTATE_DISABLE)
-			pr_info("driver is explicitly disabled\n");
-
-		if (cppc_state == AMD_PSTATE_ACTIVE)
-			current_pstate_driver = &amd_pstate_epp_driver;
-
-		if (cppc_state == AMD_PSTATE_PASSIVE || cppc_state == AMD_PSTATE_GUIDED)
-			current_pstate_driver = &amd_pstate_driver;
-
-		return 0;
-	}
-
-	return -EINVAL;
+	return amd_pstate_set_driver(mode_idx);
 }
 early_param("amd_pstate", amd_pstate_param);
 

include/linux/amd-pstate.h

@@ -94,14 +94,16 @@ struct amd_cpudata {
  * enum amd_pstate_mode - driver working mode of amd pstate
  */
 enum amd_pstate_mode {
-	AMD_PSTATE_DISABLE = 0,
+	AMD_PSTATE_UNDEFINED = 0,
+	AMD_PSTATE_DISABLE,
 	AMD_PSTATE_PASSIVE,
 	AMD_PSTATE_ACTIVE,
 	AMD_PSTATE_GUIDED,
 	AMD_PSTATE_MAX,
 };
 
 static const char * const amd_pstate_mode_string[] = {
+	[AMD_PSTATE_UNDEFINED]   = "undefined",
 	[AMD_PSTATE_DISABLE]     = "disable",
 	[AMD_PSTATE_PASSIVE]     = "passive",
 	[AMD_PSTATE_ACTIVE]      = "active",