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Message-ID: <ZfLGUHRBV+1ICzp4@BLR-5CG11610CF.amd.com>
Date: Thu, 14 Mar 2024 15:11:36 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Perry Yuan <perry.yuan@....com>
Cc: rafael.j.wysocki@...el.com, Mario.Limonciello@....com,
viresh.kumar@...aro.org, Ray.Huang@....com, Borislav.Petkov@....com,
Alexander.Deucher@....com, Xinmei.Huang@....com,
Xiaojian.Du@....com, Li.Meng@....com, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/7] cpufreq: amd-pstate: implement cpb_boost sysfs
entry for boost control
Hello Perry,
On Wed, Mar 13, 2024 at 06:04:39PM +0800, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@....com>
>
> With this new sysfs entry `cpb_boost`created, user can change CPU boost
> state dynamically under `active`, `guided` and `passive` modes.
> And the highest perf and frequency will also be updated as the boost
> state changing.
>
> 0): check current boost state
> cat /sys/devices/system/cpu/amd_pstate/cpb_boost
Could you please elaborate on the need for this new interface when
/sys/devices/system/cpu/cpufreq/boost exists and is being used in the
other cpufreq driver namely the acpi-cpufreq driver ?
The semantics of this new interface seems to be identical to the
existing boost interface.
I am ok with the rest of the patch, but please explain the need for a
new interface.
--
Thanks and Regards
gautham.
>
> 1): disable CPU boost
> sudo bash -c "echo 0 > /sys/devices/system/cpu/amd_pstate/cpb_boost"
>
> 2): enable CPU boost
> sudo bash -c "echo 1 > /sys/devices/system/cpu/amd_pstate/cpb_boost"
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217931
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217618
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
> drivers/cpufreq/amd-pstate.c | 97 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 97 insertions(+)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index ef6381b48e76..d54399ebb758 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1208,6 +1208,101 @@ static ssize_t prefcore_show(struct device *dev,
> return sysfs_emit(buf, "%s\n", str_enabled_disabled(amd_pstate_prefcore));
> }
>
> +static int amd_cpu_boost_update(struct amd_cpudata *cpudata, u32 on)
> +{
> + struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpudata->cpu);
> + struct cppc_perf_ctrls perf_ctrls;
> + u32 highest_perf, nominal_perf;
> + int ret;
> +
> + if (!policy)
> + return -ENODATA;
> +
> + highest_perf = READ_ONCE(cpudata->highest_perf);
> + nominal_perf = READ_ONCE(cpudata->nominal_perf);
> +
> + if (boot_cpu_has(X86_FEATURE_CPPC)) {
> + u64 value = READ_ONCE(cpudata->cppc_req_cached);
> +
> + value &= ~GENMASK_ULL(7, 0);
> + value |= on ? highest_perf : nominal_perf;
> + WRITE_ONCE(cpudata->cppc_req_cached, value);
> +
> + wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> +
> + } else {
> + perf_ctrls.max_perf = on ? highest_perf : nominal_perf;
> + ret = cppc_set_epp_perf(cpudata->cpu, &perf_ctrls, 1);
> + if (ret) {
> + pr_debug("failed to set energy perf value (%d)\n", ret);
> + return ret;
> + }
> + }
> +
> + if (on)
> + policy->cpuinfo.max_freq = cpudata->max_freq;
> + else
> + policy->cpuinfo.max_freq = cpudata->nominal_freq * 1000;
> +
> + policy->max = policy->cpuinfo.max_freq;
> +
> + if (cppc_state == AMD_PSTATE_PASSIVE) {
> + ret = freq_qos_update_request(&cpudata->req[1],
> + policy->cpuinfo.max_freq);
> + }
> +
> + cpufreq_cpu_release(policy);
> +
> + return ret;
> +}
> +
> +static ssize_t cpb_boost_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + return sysfs_emit(buf, "%u\n", amd_pstate_global_params.cpb_boost);
> +}
> +
> +static ssize_t cpb_boost_store(struct device *dev, struct device_attribute *b,
> + const char *buf, size_t count)
> +{
> + bool new_state;
> + ssize_t ret;
> + int cpu;
> +
> + mutex_lock(&amd_pstate_driver_lock);
> + if (!amd_pstate_global_params.cpb_supported) {
> + pr_err("Boost mode is not supported by this processor or SBIOS\n");
> + return -EINVAL;
> + }
> +
> + ret = kstrtobool(buf, &new_state);
> + if (ret)
> + return -EINVAL;
> +
> + amd_pstate_global_params.cpb_boost = !!new_state;
> +
> + for_each_online_cpu(cpu) {
> +
> + struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> + struct amd_cpudata *cpudata = policy->driver_data;
> +
> + if (!cpudata) {
> + pr_err("cpudata is NULL\n");
> + ret = -ENODATA;
> + cpufreq_cpu_put(policy);
> + goto err_exit;
> + }
> +
> + amd_cpu_boost_update(cpudata, amd_pstate_global_params.cpb_boost);
> + refresh_frequency_limits(policy);
> + cpufreq_cpu_put(policy);
> + }
> +
> +err_exit:
> + mutex_unlock(&amd_pstate_driver_lock);
> + return ret < 0 ? ret : count;
> +}
> +
> cpufreq_freq_attr_ro(amd_pstate_max_freq);
> cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
>
> @@ -1218,6 +1313,7 @@ cpufreq_freq_attr_rw(energy_performance_preference);
> cpufreq_freq_attr_ro(energy_performance_available_preferences);
> static DEVICE_ATTR_RW(status);
> static DEVICE_ATTR_RO(prefcore);
> +static DEVICE_ATTR_RW(cpb_boost);
>
> static struct freq_attr *amd_pstate_attr[] = {
> &amd_pstate_max_freq,
> @@ -1242,6 +1338,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
> static struct attribute *pstate_global_attributes[] = {
> &dev_attr_status.attr,
> &dev_attr_prefcore.attr,
> + &dev_attr_cpb_boost.attr,
> NULL
> };
>
> --
> 2.34.1
>
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