Re: [RESEND PATCH V2 6/9] cpufreq: amd_pstate: add AMD pstate EPP support for shared memory type processor

From: Huang Rui
Date: Mon Oct 17 2022 - 06:55:24 EST


On Tue, Oct 11, 2022 at 12:22:45AM +0800, Yuan, Perry wrote:
> Add Energy Performance Preference support for AMD SOCs which do not
> contain a designated MSR for CPPC support. A shared memory interface
> is used for CPPC on these SOCs and the ACPI PCC channel is used to
> enable EPP and reset the desired performance.
>
> Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> ---
> drivers/cpufreq/amd-pstate.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 2d28f458589c..08f9e335f97c 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -135,12 +135,25 @@ static inline int pstate_enable(bool enable)
>
> static int cppc_enable(bool enable)
> {
> + struct cppc_perf_ctrls perf_ctrls;
> int cpu, ret = 0;
>
> for_each_present_cpu(cpu) {
> ret = cppc_set_enable(cpu, enable);
> if (ret)
> return ret;
> + if (epp) {
> + /* Enable autonomous mode for EPP */
> + ret = cppc_set_auto_epp(cpu, enable);
> + if (ret)
> + return ret;
> +
> + /* Set desired perf as zero to allow EPP firmware control */
> + perf_ctrls.desired_perf = 0;
> + ret = cppc_set_perf(cpu, &perf_ctrls);
> + if (ret)
> + return ret;
> + }

This patch only writes the desired_perf as 0 to enable the EPP function,
but it cannot be an independent function or patch without the dependency of
the next one (patch 7).

Thanks,
Ray