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Date: Tue, 14 May 2024 10:20:55 +0530
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: Perry Yuan <perry.yuan@....com>, Mario.Limonciello@....com,
gautham.shenoy@....com, Ray.Huang@....com, Borislav.Petkov@....com
Cc: rafael.j.wysocki@...el.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 v2 01/10] cpufreq: amd-pstate: optimize the initial
frequency values verification
Hello Perry,
On 5/13/2024 7:37 AM, Perry Yuan wrote:
> To enhance the debugging capability of the driver loading failure for
> broken CPPC ACPI tables, it can optimize the expression by moving the
> verification of `min_freq`, `nominal_freq`, and other dependency values
> to the `amd_pstate_init_freq()` function where they are initialized.
> If any of these values are incorrect, the `amd-pstate` driver will not be registered.
>
> By ensuring that these values are correct before they are used, it will facilitate
> the debugging process when encountering driver loading failures due to faulty CPPC
> ACPI tables from BIOS
>
> Signed-off-by: Perry Yuan <perry.yuan@....com>
> ---
> drivers/cpufreq/amd-pstate.c | 35 ++++++++++++++++++-----------------
> 1 file changed, 18 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 6a342b0c0140..614f6fac0764 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -889,6 +889,24 @@ static int amd_pstate_init_freq(struct amd_cpudata *cpudata)
> WRITE_ONCE(cpudata->nominal_freq, nominal_freq);
> WRITE_ONCE(cpudata->max_freq, max_freq);
>
> + /**
> + * Below values need to be initialized correctly, otherwise driver will fail to load
> + * max_freq is calculated according to (nominal_freq * highest_perf)/nominal_perf
> + * lowest_nonlinear_freq is a value between [min_freq, nominal_freq]
> + * Check _CPC in ACPI table objects if any values are incorrect
> + */
> + if (min_freq <= 0 || max_freq <= 0 || nominal_freq <= 0 || min_freq > max_freq) {
> + pr_err("min_freq(%d) or max_freq(%d) or nominal_freq(%d) value is incorrect\n",
> + min_freq, max_freq, nominal_freq);
> + return -EINVAL;
> + }
> +
> + if (lowest_nonlinear_freq <= min_freq || lowest_nonlinear_freq > nominal_freq * 1000) {
> + pr_err("lowest_nonlinear_freq(%d) value is out of range [min_freq(%d), nominal_freq(%d)]\n",
> + lowest_nonlinear_freq, min_freq, nominal_freq * 1000);
A reminder, we should fix the below code section (due to only nominal freq being in MHz),
685 static int amd_pstate_set_boost(struct cpufreq_policy *policy, int state)
686 {
687 struct amd_cpudata *cpudata = policy->driver_data;
688 int ret;
689
690 if (!cpudata->boost_supported) {
691 pr_err("Boost mode is not supported by this processor or SBIOS\n");
692 return -EINVAL;
693 }
694
695 if (state)
696 policy->cpuinfo.max_freq = cpudata->max_freq;
697 else
698 policy->cpuinfo.max_freq = cpudata->nominal_freq; <--- mismatch in left and right hand side units
To avoid below situation(from a Zen4 AMD EPYC system with boost disabled),
/sys/devices/system/cpu/cpu0/cpufreq# cat scaling_max_freq
2151 <--- MHz
/sys/devices/system/cpu/cpu0/cpufreq# cat amd_pstate_max_freq
2287000 <--- KHz
Thanks,
Dhananjay
> + return -EINVAL;
> + }
> +
> return 0;
> }
>
> @@ -927,15 +945,6 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
> max_freq = READ_ONCE(cpudata->max_freq);
> nominal_freq = READ_ONCE(cpudata->nominal_freq);
>
> - if (min_freq <= 0 || max_freq <= 0 ||
> - nominal_freq <= 0 || min_freq > max_freq) {
> - dev_err(dev,
> - "min_freq(%d) or max_freq(%d) or nominal_freq (%d) value is incorrect, check _CPC in ACPI tables\n",
> - min_freq, max_freq, nominal_freq);
> - ret = -EINVAL;
> - goto free_cpudata1;
> - }
> -
> policy->cpuinfo.transition_latency = amd_pstate_get_transition_latency(policy->cpu);
> policy->transition_delay_us = amd_pstate_get_transition_delay_us(policy->cpu);
>
> @@ -1388,14 +1397,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> min_freq = READ_ONCE(cpudata->min_freq);
> max_freq = READ_ONCE(cpudata->max_freq);
> nominal_freq = READ_ONCE(cpudata->nominal_freq);
> - if (min_freq <= 0 || max_freq <= 0 ||
> - nominal_freq <= 0 || min_freq > max_freq) {
> - dev_err(dev,
> - "min_freq(%d) or max_freq(%d) or nominal_freq(%d) value is incorrect, check _CPC in ACPI tables\n",
> - min_freq, max_freq, nominal_freq);
> - ret = -EINVAL;
> - goto free_cpudata1;
> - }
>
> policy->cpuinfo.min_freq = min_freq;
> policy->cpuinfo.max_freq = max_freq;
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