linux-kernel - Re: [PATCH v2] cpufreq: amd_pstate: Fix initial highest

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Message-ID: <YwyE5UygDEhfPDVY@amd.com>
Date:   Mon, 29 Aug 2022 17:20:37 +0800
From:   Huang Rui <ray.huang@....com>
To:     "Yuan, Perry" <Perry.Yuan@....com>
Cc:     "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "Sharma, Deepak" <Deepak.Sharma@....com>,
        "Limonciello, Mario" <Mario.Limonciello@....com>,
        "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Su, Jinzhou (Joe)" <Jinzhou.Su@....com>,
        "Huang, Shimmer" <Shimmer.Huang@....com>,
        "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 v2] cpufreq: amd_pstate: Fix initial highest_perf value

On Mon, Aug 29, 2022 at 01:59:01PM +0800, Yuan, Perry wrote:
> To avoid some new AMD processors use wrong highest perf when amd pstate
> driver loaded, this fix will query the highest perf from MSR register
> MSR_AMD_CPPC_CAP1 and cppc_acpi interface firstly, then compare with the
> highest perf value got by calling amd_get_highest_perf() function.
> 
> The lower value will be the correct highest perf we need to use.
> Otherwise the CPU max MHz will be incorrect if the
> amd_get_highest_perf() did not cover the new process family and model ID.
> 
> Like this lscpu info, the max frequency is incorrect.
> 
> Vendor ID:               AuthenticAMD
>     Socket(s):           1
>     Stepping:            2
>     CPU max MHz:         5410.0000
>     CPU min MHz:         400.0000
>     BogoMIPS:            5600.54
> 
> Fixes: 3743d55b289c2 (x86, sched: Fix the AMD CPPC maximum performance value on certain AMD Ryzen generations)
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>

Acked-by: Huang Rui <ray.huang@....com>

> ---
>  drivers/cpufreq/amd-pstate.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 9f4375f7ab46..30fbd30c0949 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -354,6 +354,7 @@ static inline int amd_pstate_enable(bool enable)
>  static int pstate_init_perf(struct amd_cpudata *cpudata)
>  {
>  	u64 cap1;
> +	u32 highest_perf;
>  
>  	int ret = rdmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1,
>  				     &cap1);
> @@ -365,7 +366,11 @@ static int pstate_init_perf(struct amd_cpudata *cpudata)
>  	 *
>  	 * CPPC entry doesn't indicate the highest performance in some ASICs.
>  	 */
> -	WRITE_ONCE(cpudata->highest_perf, amd_get_highest_perf());
> +	highest_perf = amd_get_highest_perf();
> +	if (highest_perf > AMD_CPPC_HIGHEST_PERF(cap1))
> +		highest_perf = AMD_CPPC_HIGHEST_PERF(cap1);
> +
> +	WRITE_ONCE(cpudata->highest_perf, highest_perf);
>  
>  	WRITE_ONCE(cpudata->nominal_perf, AMD_CPPC_NOMINAL_PERF(cap1));
>  	WRITE_ONCE(cpudata->lowest_nonlinear_perf, AMD_CPPC_LOWNONLIN_PERF(cap1));
> @@ -377,12 +382,17 @@ static int pstate_init_perf(struct amd_cpudata *cpudata)
>  static int cppc_init_perf(struct amd_cpudata *cpudata)
>  {
>  	struct cppc_perf_caps cppc_perf;
> +	u32 highest_perf;
>  
>  	int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
>  	if (ret)
>  		return ret;
>  
> -	WRITE_ONCE(cpudata->highest_perf, amd_get_highest_perf());
> +	highest_perf = amd_get_highest_perf();
> +	if (highest_perf > cppc_perf.highest_perf)
> +		highest_perf = cppc_perf.highest_perf;
> +
> +	WRITE_ONCE(cpudata->highest_perf, highest_perf);
>  
>  	WRITE_ONCE(cpudata->nominal_perf, cppc_perf.nominal_perf);
>  	WRITE_ONCE(cpudata->lowest_nonlinear_perf,
> -- 
> 2.34.1
>