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Mon, 22 Jun 2026 15:16:49 +0000 Message-ID: <1372adf9-2356-4d0c-915d-3660efd99988@intel.com> Date: Mon, 22 Jun 2026 23:16:41 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] cpufreq: intel_pstate: Skip HWP_CAP reads in Broadwell mode To: "Rafael J. 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Wysocki wrote: > From: Rafael J. Wysocki > > When running in the Broadwell HWP mode, the turbo, max and min > P-state values are retrieved from MSR_PLATFORM_INFO, so reading > MSR_HWP_CAPABILITIES in that mode in order to update those values > is pointless. Moreover, using the MSR_HWP_CAPABILITIES value for > updating them in the Broadwell mode may be harmful, so avoid doing > that altogether. > > Fixes: de5bcf404ace ("cpufreq: intel_pstate: Clean up frequency computations") sashiko[1] reports an issue that hwp_cap_cached remains 0. Maybe still use the value from MSR_HWP_CAPABILITIES for cached value, which was what we did before commit de5bcf404ace? I fed this to AI and was given the following: diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 5a0eeb84d382..a373a199c9c6 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -1189,6 +1189,8 @@ static void __intel_pstate_get_hwp_cap(struct cpudata *cpu) rdmsrq_on_cpu(cpu->cpu, MSR_HWP_CAPABILITIES, &cap); WRITE_ONCE(cpu->hwp_cap_cached, cap); + if (hwp_mode_bdw) + return; cpu->pstate.max_pstate = HWP_GUARANTEED_PERF(cap); cpu->pstate.turbo_pstate = HWP_HIGHEST_PERF(cap); } @@ -1199,6 +1201,9 @@ static void intel_pstate_get_hwp_cap(struct cpudata *cpu) __intel_pstate_get_hwp_cap(cpu); + if (hwp_mode_bdw) + return; + cpu->pstate.max_freq = cpu->pstate.max_pstate * scaling; cpu->pstate.turbo_freq = cpu->pstate.turbo_pstate * scaling; if (scaling != cpu->pstate.perf_ctl_scaling) { [1] https://sashiko.dev/#/patchset/12920597.O9o76ZdvQC%40rafael.j.wysocki thanks, Chenyu