linux-kernel - [PATCH v12 7/8] cppc_acpi: print error message if CPPC is unsupported

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Message-ID: <b254f5d823cdd5dd380483425349aaf4aa6432c4.1714032153.git.perry.yuan@amd.com>
Date: Thu, 25 Apr 2024 16:07:57 +0800
From: Perry Yuan <perry.yuan@....com>
To: <rafael.j.wysocki@...el.com>, <Mario.Limonciello@....com>,
	<viresh.kumar@...aro.org>, <gautham.shenoy@....com>,
	<Borislav.Petkov@....com>, <Ray.Huang@....com>, <Alexander.Deucher@....com>
CC: <Xinmei.Huang@....com>, <oleksandr@...alenko.name>, <Xiaojian.Du@....com>,
	<Li.Meng@....com>, <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v12 7/8] cppc_acpi: print error message if CPPC is unsupported

The amd-pstate driver can fail when _CPC objects are not supported by
the CPU. However, the current error message is ambiguous (see below) and
there is no clear way for attributing the failure of the amd-pstate
driver to the lack of CPPC support.

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

Fix this by adding an debug message to notify the user if the amd-pstate
driver failed to load due to CPPC not be supported by the CPU

Reviewed-by: Mario Limonciello <mario.limonciello@....com>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
Tested-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
Signed-off-by: Perry Yuan <perry.yuan@....com>
Acked-by: Huang Rui <ray.huang@....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 a40b6f3946ef..1d857978f5f4 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -686,8 +686,10 @@ 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