linux-kernel - [PATCH v4 5/6] cppc_acpi: print error message if CPPC is unsupported

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Message-ID: <2343f6c652bbcfad9cb462b5fd05fdb49e833e1f.1707193566.git.perry.yuan@amd.com>
Date: Tue, 6 Feb 2024 12:33:58 +0800
From: Perry Yuan <perry.yuan@....com>
To: <rafael.j.wysocki@...el.com>, <Mario.Limonciello@....com>,
	<viresh.kumar@...aro.org>, <Ray.Huang@....com>, <gautham.shenoy@....com>,
	<Borislav.Petkov@....com>
CC: <Alexander.Deucher@....com>, <Xinmei.Huang@....com>,
	<Xiaojian.Du@....com>, <Li.Meng@....com>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH v4 5/6] cppc_acpi: print error message if CPPC is unsupported

to be more clear what is wrong with CPPC when pstate driver failed to
load which has dependency on the CPPC capabilities.

Add one more debug message to notify user if CPPC is not supported by
the CPU, then it will be easy to find out what need to fix for pstate
driver loading issue.

[    0.477523] amd_pstate: the _CPC object is not present in SBIOS or ACPI disabled

Above message is not clear enough to verify whether CPPC is not supported.

Reviewed-by: Mario Limonciello <mario.limonciello@....com>
Signed-off-by: Perry Yuan <perry.yuan@....com>
---
 drivers/acpi/cppc_acpi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index a50e70abdf19..e23a84f4a50a 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -679,8 +679,10 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 
 	if (!osc_sb_cppc2_support_acked) {
 		pr_debug("CPPC v2 _OSC not acked\n");
-		if (!cpc_supported_by_cpu())
+		if (!cpc_supported_by_cpu()) {
+			pr_debug("CPPC is not supported by the CPU\n");
 			return -ENODEV;
+		}
 	}
 
 	/* Parse the ACPI _CPC table for this CPU. */
-- 
2.34.1