linux-kernel - Re: [PATCH 05/15] cpufreq/amd-pstate: Store the boost numerator as highest perf again

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Message-ID: <Z1KYvREbwjWspe+/@BLRRASHENOY1.amd.com>
Date: Fri, 6 Dec 2024 11:55:01 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Perry Yuan <perry.yuan@....com>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org,
	Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
Subject: Re: [PATCH 05/15] cpufreq/amd-pstate: Store the boost numerator as
 highest perf again

On Thu, Dec 05, 2024 at 04:28:37PM -0600, Mario Limonciello wrote:
> commit ad4caad58d91d ("cpufreq: amd-pstate: Merge
> amd_pstate_highest_perf_set() into amd_get_boost_ratio_numerator()")
> changed the semantics for highest perf and commit 18d9b52271213
> ("cpufreq/amd-pstate: Use nominal perf for limits when boost is disabled")
> worked around those semantic changes.
> 
> This however is a confusing result and furthermore makes it awkward to
> change frequency limits and boost due to the scaling differences. Restore
> the boost numerator to highest perf again.

The patch looks good to me.

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>

--
Thanks and Regards
gautham.


> 
> Suggested-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
> Fixes: ad4caad58d91 ("cpufreq: amd-pstate: Merge amd_pstate_highest_perf_set() into amd_get_boost_ratio_numerator()")
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  Documentation/admin-guide/pm/amd-pstate.rst |  4 +---
>  drivers/cpufreq/amd-pstate.c                | 25 ++++++++++++---------
>  2 files changed, 16 insertions(+), 13 deletions(-)
> 
> diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
> index 210a808b74ec2..412423c54f258 100644
> --- a/Documentation/admin-guide/pm/amd-pstate.rst
> +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> @@ -251,9 +251,7 @@ performance supported in `AMD CPPC Performance Capability <perf_cap_>`_).
>  In some ASICs, the highest CPPC performance is not the one in the ``_CPC``
>  table, so we need to expose it to sysfs. If boost is not active, but
>  still supported, this maximum frequency will be larger than the one in
> -``cpuinfo``. On systems that support preferred core, the driver will have
> -different values for some cores than others and this will reflect the values
> -advertised by the platform at bootup.
> +``cpuinfo``.
>  This attribute is read-only.
>  
>  ``amd_pstate_lowest_nonlinear_freq``
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index dbe014f3c2beb..738f63d70546f 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -408,15 +408,19 @@ static inline int amd_pstate_cppc_enable(bool enable)
>  
>  static int msr_init_perf(struct amd_cpudata *cpudata)
>  {
> -	u64 cap1;
> +	u64 cap1, numerator;
>  
>  	int ret = rdmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1,
>  				     &cap1);
>  	if (ret)
>  		return ret;
>  
> -	WRITE_ONCE(cpudata->highest_perf, AMD_CPPC_HIGHEST_PERF(cap1));
> -	WRITE_ONCE(cpudata->max_limit_perf, AMD_CPPC_HIGHEST_PERF(cap1));
> +	ret = amd_get_boost_ratio_numerator(cpudata->cpu, &numerator);
> +	if (ret)
> +		return ret;
> +
> +	WRITE_ONCE(cpudata->highest_perf, numerator);
> +	WRITE_ONCE(cpudata->max_limit_perf, numerator);
>  	WRITE_ONCE(cpudata->nominal_perf, AMD_CPPC_NOMINAL_PERF(cap1));
>  	WRITE_ONCE(cpudata->lowest_nonlinear_perf, AMD_CPPC_LOWNONLIN_PERF(cap1));
>  	WRITE_ONCE(cpudata->lowest_perf, AMD_CPPC_LOWEST_PERF(cap1));
> @@ -428,13 +432,18 @@ static int msr_init_perf(struct amd_cpudata *cpudata)
>  static int shmem_init_perf(struct amd_cpudata *cpudata)
>  {
>  	struct cppc_perf_caps cppc_perf;
> +	u64 numerator;
>  
>  	int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
>  	if (ret)
>  		return ret;
>  
> -	WRITE_ONCE(cpudata->highest_perf, cppc_perf.highest_perf);
> -	WRITE_ONCE(cpudata->max_limit_perf, cppc_perf.highest_perf);
> +	ret = amd_get_boost_ratio_numerator(cpudata->cpu, &numerator);
> +	if (ret)
> +		return ret;
> +
> +	WRITE_ONCE(cpudata->highest_perf, numerator);
> +	WRITE_ONCE(cpudata->max_limit_perf, numerator);
>  	WRITE_ONCE(cpudata->nominal_perf, cppc_perf.nominal_perf);
>  	WRITE_ONCE(cpudata->lowest_nonlinear_perf,
>  		   cppc_perf.lowest_nonlinear_perf);
> @@ -920,7 +929,6 @@ static int amd_pstate_init_freq(struct amd_cpudata *cpudata)
>  {
>  	int ret;
>  	u32 min_freq, max_freq;
> -	u64 numerator;
>  	u32 nominal_perf, nominal_freq;
>  	u32 lowest_nonlinear_perf, lowest_nonlinear_freq;
>  	u32 boost_ratio, lowest_nonlinear_ratio;
> @@ -942,10 +950,7 @@ static int amd_pstate_init_freq(struct amd_cpudata *cpudata)
>  
>  	nominal_perf = READ_ONCE(cpudata->nominal_perf);
>  
> -	ret = amd_get_boost_ratio_numerator(cpudata->cpu, &numerator);
> -	if (ret)
> -		return ret;
> -	boost_ratio = div_u64(numerator << SCHED_CAPACITY_SHIFT, nominal_perf);
> +	boost_ratio = div_u64(cpudata->highest_perf << SCHED_CAPACITY_SHIFT, nominal_perf);
>  	max_freq = (nominal_freq * boost_ratio >> SCHED_CAPACITY_SHIFT) * 1000;
>  
>  	lowest_nonlinear_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);
> -- 
> 2.43.0
>