RE: [PATCH] [PATCH] amd_pstate: fix erroneous highest_perf value on some CPUs

[AMD Official Use Only - General]

Hi Lucas:

-----Original Message----- From: Lucas Lee Jing Yi lucasleeeeeeeee@gmail.com Sent: Monday, February 19, 2024 12:11 AM To: rafael@kernel.org Cc: Yuan, Perry Perry.Yuan@amd.com; Du, Xiaojian Xiaojian.Du@amd.com; Deucher, Alexander Alexander.Deucher@amd.com; bp@alien8.de; Sharma, Deepak Deepak.Sharma@amd.com; Meng, Li (Jassmine) Li.Meng@amd.com; linux-acpi@vger.kernel.org; linux-kernel@vger.kernel.org; linux- kselftest@vger.kernel.org; linux-pm@vger.kernel.org; Limonciello, Mario Mario.Limonciello@amd.com; Fontenot, Nathan Nathan.Fontenot@amd.com; oleksandr@natalenko.name; rafael.j.wysocki@intel.com; Huang, Ray Ray.Huang@amd.com; Huang, Shimmer Shimmer.Huang@amd.com; skhan@linuxfoundation.org; viresh.kumar@linaro.org; x86@kernel.org; Lucas Lee Jing Yi lucasleeeeeeeee@gmail.com Subject: [PATCH] [PATCH] amd_pstate: fix erroneous highest_perf value on some CPUs

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On a Ryzen 7840HS the highest_perf value is 196, not 166 as AMD assumed. This leads to the advertised max clock speed to only be 4.35ghz instead of 5.14ghz , leading to a large degradation in performance.

Fix the broken assumption and revert back to the old logic for getting highest_perf.

TEST: Geekbench 6 Before Patch: Single Core: 2325 (-22%)! Multi Core: 11335 (-10%)

Geekbench 6 AFTER Patch: Single Core: 2635 Multi Core: 12487

Signed-off-by: Lucas Lee Jing Yi lucasleeeeeeeee@gmail.com

drivers/cpufreq/amd-pstate.c | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index 08e112444c27..54df68773620 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -50,7 +50,6 @@

#define AMD_PSTATE_TRANSITION_LATENCY 20000 #define AMD_PSTATE_TRANSITION_DELAY 1000 -#define AMD_PSTATE_PREFCORE_THRESHOLD 166

/*

• TODO: We need more time to fine tune processors with shared memory

solution @@ -299,15 +298,12 @@ static int pstate_init_perf(struct amd_cpudata *cpudata) &cap1); if (ret) return ret;

•   /* For platforms that do not support the preferred core feature, the
  

•    * highest_pef may be configured with 166 or 255, to avoid max
  

frequency

•    * calculated wrongly. we take the AMD_CPPC_HIGHEST_PERF(cap1)
  

value as

•    * the default max perf.
  

•   /* Some CPUs have different highest_perf from others, it is safer
  

•    * to read it than to assume some erroneous value, leading to
  

performance issues. */

•   if (cpudata->hw_prefcore)
  

•           highest_perf = AMD_PSTATE_PREFCORE_THRESHOLD;
  

•   else
  

•   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); @@ -329,9 +325,11
  

@@ static int cppc_init_perf(struct amd_cpudata *cpudata) if (ret) return ret;

•   if (cpudata->hw_prefcore)
  

•           highest_perf = AMD_PSTATE_PREFCORE_THRESHOLD;
  

•   else
  

•   /* Some CPUs have different highest_perf from others, it is safer
  

•    * to read it than to assume some erroneous value, leading to
  

performance issues.

•    */
  

•   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);
  

-- 2.43.2

[Meng, Li (Jassmine)] Reviewed-by: Li Meng < li.meng@amd.com>