diff mbox series

[v5,4/8] cpufreq: amd-pstate: add debug message while CPPC is supported and disabled by SBIOS

Message ID 42c953616ac121bd1e5c329e83d015a02e6b32c7.1718811234.git.perry.yuan@amd.com
State New
Headers show
Series AMD Pstate Driver Fixes and Improvements | expand

Commit Message

Yuan, Perry June 19, 2024, 3:40 p.m. UTC 
If CPPC feature is supported by the CPU however the CPUID flag bit is not
set by SBIOS, the `amd_pstate` will be failed to load while system
booting.
So adding one more debug message to inform user to check the SBIOS setting,
The change also can help maintainers to debug why amd_pstate driver failed
to be loaded at system booting if the processor support CPPC.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218686
Signed-off-by: Perry Yuan <perry.yuan@amd.com>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Acked-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/cpufreq/amd-pstate.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
diff mbox series

Patch

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 76419762c04f..9aa220a0e3fe 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1749,11 +1749,37 @@  static int __init amd_pstate_set_driver(int mode_idx)
  */
 static bool amd_cppc_supported(void)
 {
+	struct cpuinfo_x86 *c = &cpu_data(0);
+	bool warn = false;
+
 	if ((boot_cpu_data.x86 == 0x17) && (boot_cpu_data.x86_model < 0x30)) {
 		pr_debug_once("CPPC feature is not supported by the processor\n");
 		return false;
 	}
 
+	/*
+	 * If the CPPC feature is disabled in the BIOS for processors that support MSR-based CPPC,
+	 * the AMD Pstate driver may not function correctly.
+	 * Check the CPPC flag and display a warning message if the platform supports CPPC.
+	 * Note: below checking code will not abort the driver registeration process because of
+	 * the code is added for debugging purposes.
+	 */
+	if (!cpu_feature_enabled(X86_FEATURE_CPPC)) {
+		if (cpu_feature_enabled(X86_FEATURE_ZEN1) || cpu_feature_enabled(X86_FEATURE_ZEN2)) {
+			if (c->x86_model > 0x60 && c->x86_model < 0xaf)
+				warn = true;
+		} else if (cpu_feature_enabled(X86_FEATURE_ZEN3) || cpu_feature_enabled(X86_FEATURE_ZEN4)) {
+			if ((c->x86_model > 0x10 && c->x86_model < 0x1F) ||
+					(c->x86_model > 0x40 && c->x86_model < 0xaf))
+				warn = true;
+		} else if (cpu_feature_enabled(X86_FEATURE_ZEN5)) {
+			warn = true;
+		}
+	}
+
+	if (warn)
+		pr_warn_once("The CPPC feature is supported but currently disabled by the BIOS.\n"
+					"Please enable it if your BIOS has the CPPC option.\n");
 	return true;
 }