linux-kernel - Re: [PATCH v10 7/8] cppc_acpi: print error message if CPPC is unsupported

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Date: Mon, 15 Apr 2024 23:04:04 +0800
From: Huang Rui <ray.huang@....com>
To: "Yuan, Perry" <Perry.Yuan@....com>
Cc: "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
	"Limonciello, Mario" <Mario.Limonciello@....com>,
	"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
	"Shenoy, Gautham Ranjal" <gautham.shenoy@....com>,
	"Petkov, Borislav" <Borislav.Petkov@....com>,
	"Deucher, Alexander" <Alexander.Deucher@....com>,
	"Huang, Shimmer" <Shimmer.Huang@....com>,
	"oleksandr@...alenko.name" <oleksandr@...alenko.name>,
	"Du, Xiaojian" <Xiaojian.Du@....com>,
	"Meng, Li (Jassmine)" <Li.Meng@....com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 7/8] cppc_acpi: print error message if CPPC is
 unsupported

On Mon, Mar 25, 2024 at 11:03:27AM +0800, Yuan, Perry wrote:
> 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 4bfbe55553f4..3134101f31b6 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
>