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Message-ID: <e32c77c2-6284-44e5-8224-c3484d8631c9@amd.com>
Date: Wed, 19 Jun 2024 14:32:52 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Perry Yuan <perry.yuan@....com>, rafael.j.wysocki@...el.com,
viresh.kumar@...aro.org, gautham.shenoy@....com
Cc: Xinmei.Huang@....com, Xiaojian.Du@....com, Li.Meng@....com,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 4/9] cpufreq: amd-pstate: initialize new core
precision boost state
On 6/19/2024 04:16, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@....com>
>
> Add one global `global_params` to represent CPU Performance Boost(cpb)
> state for cpu frequency scaling, both active and passive modes all can
> support CPU cores frequency boosting control which is based on the BIOS
> setting, while BIOS turn on the "Core Performance Boost", it will
> allow OS control each core highest perf limitation from OS side.
>
> The active, guided and passive modes of the amd-pstate driver can
> support frequency boost control when the "Core Performance Boost"
> (CPB) feature is enabled in the BIOS. When enabled in BIOS, the user
> has an option at runtime to allow/disallow the cores from operating in
> the boost frequency range.
>
> Add an amd_pstate_global_params object to record whether CPB is
> enabled in BIOS, and if it has been activated by the user
>
> Reported-by: Artem S. Tashkinov" <aros@....com>
> Cc: Oleksandr Natalenko <oleksandr@...alenko.name>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217931
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
> drivers/cpufreq/amd-pstate.c | 59 +++++++++++++++++++++++++++++-------
> drivers/cpufreq/amd-pstate.h | 13 ++++++++
> 2 files changed, 61 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 5bdcdd3ea163..0c50b8ba16b6 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -102,6 +102,8 @@ static int cppc_state = AMD_PSTATE_UNDEFINED;
> static bool cppc_enabled;
> static bool amd_pstate_prefcore = true;
> static struct quirk_entry *quirks;
> +struct amd_pstate_global_params amd_pstate_global_params;
> +EXPORT_SYMBOL_GPL(amd_pstate_global_params);
>
> /*
> * AMD Energy Preference Performance (EPP)
> @@ -694,7 +696,7 @@ static int amd_pstate_set_boost(struct cpufreq_policy *policy, int state)
>
> if (!cpudata->boost_supported) {
> pr_err("Boost mode is not supported by this processor or SBIOS\n");
> - return -EINVAL;
> + return -ENOTSUPP;
You're using -ENOTSUPP here and -EOPNOTSUPP in amd_pstate_boost_set().
You should be consistent with these error codes. That being said I
think the other error flow needs to go. More on that below.
> }
>
> if (state)
> @@ -712,18 +714,38 @@ static int amd_pstate_set_boost(struct cpufreq_policy *policy, int state)
> return 0;
> }
>
> -static void amd_pstate_boost_init(struct amd_cpudata *cpudata)
> +static int amd_pstate_boost_set(struct amd_cpudata *cpudata)
> {
> - u32 highest_perf, nominal_perf;
> + u64 boost_val;
> + int ret = -1;
>
> - highest_perf = READ_ONCE(cpudata->highest_perf);
> - nominal_perf = READ_ONCE(cpudata->nominal_perf);
> + if (!cpu_feature_enabled(X86_FEATURE_CPB)) {
> + pr_debug_once("Boost CPB capabilities not present in the processor\n");
> + ret = -EOPNOTSUPP;
> + goto exit_err;
> + }
This needs a little bit of unwinding to think about whether it's correct
return code.
This is the call path:
cpufreq_driver->init_boost();
-> amd_pstate_init_boost()
->-> amd_pstate_boost_set()
So if we end up with a platform that supports CPPC but doesn't support
boost we might end up nuking the amd-pstate support "because" of the
lack of boost.
For this reason I think it's better to set the return code to 0 in this
specific place. The others in this function look correct to me and if
fail should cause a critical problem with setting up CPPC.
>
> - if (highest_perf <= nominal_perf)
> - return;
> + ret = rdmsrl_on_cpu(cpudata->cpu, MSR_K7_HWCR, &boost_val);
> + if (ret) {
> + pr_err_once("failed to read initial CPU boost state!\n");
> + ret = -EIO;
> + goto exit_err;
> + }
> +
> + amd_pstate_global_params.cpb_supported = !(boost_val & MSR_K7_HWCR_CPB_DIS);
> + if (amd_pstate_global_params.cpb_supported) {
> + current_pstate_driver->boost_enabled = true;
> + WRITE_ONCE(cpudata->boost_supported, true);
> + }
>
> - cpudata->boost_supported = true;
> - current_pstate_driver->boost_enabled = true;
> + amd_pstate_global_params.cpb_boost = amd_pstate_global_params.cpb_supported;
> + return 0;
> +
> +exit_err:
> + WRITE_ONCE(cpudata->boost_supported, false);
> + current_pstate_driver->boost_enabled = false;
> + amd_pstate_global_params.cpb_boost = false;
> + return ret;
> }
>
> static void amd_perf_ctl_reset(unsigned int cpu)
> @@ -1005,7 +1027,6 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
>
> policy->driver_data = cpudata;
>
> - amd_pstate_boost_init(cpudata);
> if (!current_pstate_driver->adjust_perf)
> current_pstate_driver->adjust_perf = amd_pstate_adjust_perf;
>
> @@ -1387,6 +1408,21 @@ static bool amd_pstate_acpi_pm_profile_undefined(void)
> return false;
> }
>
> +static int amd_pstate_init_boost(struct cpufreq_policy *policy)
> +{
> + struct amd_cpudata *cpudata = policy->driver_data;
> + int ret;
> +
> + /* initialize cpu cores boot state */
> + ret = amd_pstate_boost_set(cpudata);
> + if (ret)
> + return ret;
> +
> + policy->boost_enabled = READ_ONCE(cpudata->boost_supported);
> +
> + return 0;
> +}
> +
> static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> {
> int min_freq, max_freq, nominal_freq, ret;
> @@ -1465,7 +1501,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> return ret;
> WRITE_ONCE(cpudata->cppc_cap1_cached, value);
> }
> - amd_pstate_boost_init(cpudata);
>
> return 0;
>
> @@ -1704,6 +1739,7 @@ static struct cpufreq_driver amd_pstate_driver = {
> .exit = amd_pstate_cpu_exit,
> .suspend = amd_pstate_cpu_suspend,
> .resume = amd_pstate_cpu_resume,
> + .init_boost = amd_pstate_init_boost,
> .set_boost = amd_pstate_set_boost,
> .update_limits = amd_pstate_update_limits,
> .name = "amd-pstate",
> @@ -1721,6 +1757,7 @@ static struct cpufreq_driver amd_pstate_epp_driver = {
> .suspend = amd_pstate_epp_suspend,
> .resume = amd_pstate_epp_resume,
> .update_limits = amd_pstate_update_limits,
> + .init_boost = amd_pstate_init_boost,
> .name = "amd-pstate-epp",
> .attr = amd_pstate_epp_attr,
> };
> diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
> index f80b33fa5d43..133042370a8f 100644
> --- a/drivers/cpufreq/amd-pstate.h
> +++ b/drivers/cpufreq/amd-pstate.h
> @@ -102,4 +102,17 @@ struct amd_cpudata {
> s16 epp_default;
> };
>
> +/**
> + * struct amd_pstate_global_params - Global parameters, mostly tunable via sysfs.
> + * @cpb_boost: Whether or not to use boost CPU P-states.
> + * @cpb_supported: Whether or not CPU boost P-states are available
> + * based on the MSR_K7_HWCR bit[25] state
> + */
> +struct amd_pstate_global_params {
> + bool cpb_boost;
> + bool cpb_supported;
> +};
> +
> +extern struct amd_pstate_global_params amd_pstate_global_params;
> +
> #endif /* _LINUX_AMD_PSTATE_H */
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