Re: [PATCH v4 04/13] cpufreq: amd-pstate: prefetch cppc_req_cached value in amd_pstate_cpu_init()

Huang Rui
2022-07-19T00:49:05Z

On Fri, Jul 15, 2022 at 06:04:23PM +0800, Yuan, Perry wrote:
> This cppc_req_cached valued should be prefetched during
> amd_pstate_cpu_init call period, then the amd_pstate_update() will get
> correct cached value before updating the perf to change the cpu perf
> level.The cached values are read through MSR interface, so here use
> shared_mem flag to check the registers are accessible
>
> Also the core performance boost state will be initialized through
> hardware configuration register
>
> * shared_mem flag is used for the shared memory type CPPC implementation
> which dose not support MSR interface operation

Please check the comment of patch 2.

>
> Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> ---
> drivers/cpufreq/amd-pstate.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 43e6df9f67f6..d8c4153dbe4f 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -92,6 +92,8 @@ struct amd_aperf_mperf {
> * @prev: Last Aperf/Mperf/tsc count value read from register
> * @freq: current cpu frequency value
> * @boost_supported: check whether the Processor or SBIOS supports boost mode
> + * @precision_boost_off: the core performance boost disabled state
> + * @cppc_hw_conf_cached: the cached hardware configuration register
> *
> * The amd_cpudata is key private data for each CPU thread in AMD P-State, and
> * represents all the attributes and goals that AMD P-State requests at runtime.
> @@ -117,6 +119,7 @@ struct amd_cpudata {
>
> u64 freq;
> bool boost_supported;
> + bool precision_boost_off;
> u64 cppc_hw_conf_cached;
> };
>
> @@ -547,12 +550,17 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
> cpudata->lowest_nonlinear_freq = lowest_nonlinear_freq;
>
> policy->driver_data = cpudata;
> + if (!shared_mem) {
> + ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_HW_CTL, &value);
> + if (ret)
> + return ret;
> + cpudata->precision_boost_off = value & AMD_CPPC_PRECISION_BOOST_ENABLED;
>
> - ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_HW_CTL, &value);
> - if (ret)
> - return ret;
> - WRITE_ONCE(cpudata->cppc_hw_conf_cached, value);
> -
> + ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, &value);
> + if (ret)
> + return ret;
> + WRITE_ONCE(cpudata->cppc_req_cached, value);
> + }
> amd_pstate_boost_init(cpudata);
>
> return 0;
> --
> 2.32.0
>