[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <580bc2a0-8621-4147-a7dd-0cc0bd54f9fa@amd.com>
Date: Fri, 26 Jan 2024 09:52:51 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: Perry Yuan <perry.yuan@....com>, rafael.j.wysocki@...el.com,
viresh.kumar@...aro.org, Ray.Huang@....com, gautham.shenoy@....com,
Borislav.Petkov@....com
Cc: 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 6/7] cpufreq:amd-pstate: add suspend and resume callback
for passive mode
On 1/26/2024 02:08, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@....com>
>
> Add suspend and resume support for `passive` mode driver which can save
> the previous CPU Pstate values and restore them while resuming, on some
> old platforms, the highest perf needs to be restored from driver side,
> otherwise the highest frequency could be changed during suspend.
So this sounds like a BIOS bug, right? Do you know how far back this
problem exists? Should it be a quirked behavior to only run on the
broken platforms so we don't need to run the callback on modern ones
without it?
>
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
> drivers/cpufreq/amd-pstate.c | 48 ++++++++++++++++++++++++++++++++----
> 1 file changed, 43 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 5cbbc2999d9a..bba7640d46e0 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -785,23 +785,61 @@ static int amd_pstate_cpu_exit(struct cpufreq_policy *policy)
>
> static int amd_pstate_cpu_resume(struct cpufreq_policy *policy)
> {
> + struct cppc_perf_ctrls perf_ctrls;
> + struct amd_cpudata *cpudata = policy->driver_data;
> + u64 value, max_perf;
> int ret;
>
> - ret = amd_pstate_enable(true);
> - if (ret)
> - pr_err("failed to enable amd-pstate during resume, return %d\n", ret);
> + if (cpudata->suspended) {
> + mutex_lock(&amd_pstate_driver_lock);
>
> - return ret;
> + ret = amd_pstate_enable(true);
> + if (ret) {
> + pr_err("failed to enable amd-pstate during resume, return %d\n", ret);
> + mutex_unlock(&amd_pstate_driver_lock);
> + return ret;
> + }
This /looks/ like an unintended logic change to me. Previously
amd_pstate_enable(true) would be called in all modes, but now it will
only be called in passive mode.
Is that right?
> +
> + value = READ_ONCE(cpudata->cppc_req_cached);
> + max_perf = READ_ONCE(cpudata->highest_perf);
> +
> + if (boot_cpu_has(X86_FEATURE_CPPC)) {
> + wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> + } else {
> + perf_ctrls.max_perf = max_perf;
> + cppc_set_perf(cpudata->cpu, &perf_ctrls);
> + }
> +
> + cpudata->suspended = false;
> + mutex_unlock(&amd_pstate_driver_lock);
> + }
> +
> + return 0;
> }
>
> static int amd_pstate_cpu_suspend(struct cpufreq_policy *policy)
> {
> + struct amd_cpudata *cpudata = policy->driver_data;
> int ret;
>
> + /* avoid suspending when EPP is not enabled */
The logic seems right, but shouldn't the comment be:
/* only run suspend callbacks for passive mode */
Because this stuff won't run in guided mode or disable mode either
> + if (cppc_state != AMD_PSTATE_PASSIVE)
> + return 0;
> +
> + mutex_lock(&amd_pstate_driver_lock);
> +
> + /* set this flag to avoid calling core offline function
> + * when system is suspending, use this flag to skip offline function
> + * called
> + */
> + cpudata->suspended = true;
> +
> ret = amd_pstate_enable(false);
> if (ret)
> pr_err("failed to disable amd-pstate during suspend, return %d\n", ret);
>
> + mutex_unlock(&amd_pstate_driver_lock);
> +
> return ret;
> }
>
> @@ -1460,7 +1498,7 @@ static int amd_pstate_epp_suspend(struct cpufreq_policy *policy)
> if (cppc_state != AMD_PSTATE_ACTIVE)
> return 0;
>
> - /* set this flag to avoid setting core offline*/
> + /* set this flag to avoid setting core offline */
> cpudata->suspended = true;
>
> /* disable CPPC in lowlevel firmware */
Powered by blists - more mailing lists