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@amd.com>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Tested-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
Signed-off-by: Perry Yuan <perry.yuan@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 4bfbe55553f410119378fc3bbf8c73b9d6717a05..3134101f31b69f95710d17e6ef8b731d20bd9226 100644 (file)
--- 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. */