linux-kernel - Re: [PATCH 3/3] cpufreq/amd-pstate: Remove warning for X86_FEATURE

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Message-ID: <9ca4054e-a130-b65b-d2f3-3ef84c997dfd@amd.com>
Date: Wed, 14 Aug 2024 17:29:04 +0800
From: Xiaojian Du <xiaojidu@....com>
To: "Gautham R. Shenoy" <gautham.shenoy@....com>,
 "Rafael J . Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Mario Limonciello <mario.limonciello@....com>, Huang Rui
 <ray.huang@....com>, Perry Yuan <perry.yuan@....com>,
 Dan Carpenter <dan.carpenter@...aro.org>,
 Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>, David Wang <00107082@....com>
Subject: Re: [PATCH 3/3] cpufreq/amd-pstate: Remove warning for
 X86_FEATURE_CPPC on Zen1 and Zen2

Hi Gautham,

On 2024/8/13 17:54, Gautham R. Shenoy wrote:
> ...
>
> This feature bit corresponds to CPUID 0x80000008.ebx[27] which is a
> reserved bit on the Zen1 and Zen2 platforms, and is expected to be
> cleared on these platforms. Thus printing the warning message for Zen1
> and Zen2 models when X86_FEATURE_CPPC is incorrect. Fix this.
>
> ...
>   	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;

Some models of ZEN2 APU/CPU require this warning info, like Renoir 
(Ryzen 7 4800H mobile APU/4750G desktop APU,
Ryzen 5 4600 desktop CPU), Lucienne (Ryzen 5 5500U mobile APU) and 
Aerith (APU of Steam Deck console).

So it has to use model ID to narrow down the coverage.

For ZEN1 APU/CPU, this warning can be removed completely, because ZEN1 
doesn't support CPPC.

Thanks,
Xiaojian

> -		} else if (cpu_feature_enabled(X86_FEATURE_ZEN3) || cpu_feature_enabled(X86_FEATURE_ZEN4)) {
> +		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;