Re: [PATCH v3 01/18] cpufreq/amd-pstate: Invalidate cppc_req_cached during suspend

From: Gautham R. Shenoy
Date: Wed Feb 19 2025 - 00:24:40 EST


Hello Mario,


On Mon, Feb 17, 2025 at 04:06:50PM -0600, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@xxxxxxx>
>
> During resume it's possible the firmware didn't restore the CPPC request MSR
> but the kernel thinks the values line up. This leads to incorrect performance
> after resume from suspend.
>
> To fix the issue invalidate the cached value at suspend. During resume use
> the saved values programmed as cached limits.
>
> Reported-by: Miroslav Pavleski <miroslav@xxxxxxxxxxxx>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217931
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> ---
> drivers/cpufreq/amd-pstate.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index f425fb7ec77d7..12fb63169a24c 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1611,7 +1611,7 @@ static int amd_pstate_epp_reenable(struct cpufreq_policy *policy)
> max_perf, policy->boost_enabled);
> }

You can also remove the tracing code from amd_pstate_epp_reenable(), i.e,

if (trace_amd_pstate_epp_perf_enabled()) {
trace_amd_pstate_epp_perf(cpudata->cpu, cpudata->highest_perf,
cpudata->epp_cached,
FIELD_GET(AMD_CPPC_MIN_PERF_MASK, cpudata->cppc_req_cached),
max_perf, policy->boost_enabled);
}

Since amd_pstate_epp_update_limit() also has the the tracing code.

The patch looks good to me otherwise.

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

--
Thanks and Regards
gautham.



>
> - return amd_pstate_update_perf(cpudata, 0, 0, max_perf, cpudata->epp_cached, false);
> + return amd_pstate_epp_update_limit(policy);
> }
>
> static int amd_pstate_epp_cpu_online(struct cpufreq_policy *policy)
> @@ -1660,6 +1660,9 @@ static int amd_pstate_epp_suspend(struct cpufreq_policy *policy)
> if (cppc_state != AMD_PSTATE_ACTIVE)
> return 0;
>
> + /* invalidate to ensure it's rewritten during resume */
> + cpudata->cppc_req_cached = 0;
> +
> /* set this flag to avoid setting core offline*/
> cpudata->suspended = true;
>
> --
> 2.43.0
>