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SubjectRe: [PATCH 6/6] cpufreq:amd-pstate: add quirk for the pstate CPPC capabilities missing
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On 1/31/2024 02:50, Perry Yuan wrote:
> Add quirk table to get CPPC capabilities issue fixed by providing
> correct perf or frequency values while driver loading.
>
> If CPPC capabilities are not defined in the ACPI tables or wrongly
> defined by platform firmware, it needs to use quick to get those

s/quick/quirk/

> issues fixed with correct workaround values to make pstate driver

to allow the pstate driver

> can be loaded even though there are CPPC capabilities errors.
>
> Signed-off-by: Perry Yuan <perry.yuan@amd.com>
> ---
> drivers/cpufreq/amd-pstate.c | 51 +++++++++++++++++++++++++++++++-----
> include/linux/amd-pstate.h | 6 +++++
> 2 files changed, 51 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index eea2e192d748..cbc415af0f08 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -64,6 +64,7 @@ static struct cpufreq_driver amd_pstate_driver;
> static struct cpufreq_driver amd_pstate_epp_driver;
> static int cppc_state = AMD_PSTATE_UNDEFINED;
> static bool cppc_enabled;
> +static struct quirk_entry *quirks;
>
> /**
> * struct global_params - Global parameters, mostly tunable via sysfs.
> @@ -121,6 +122,32 @@ static unsigned int epp_values[] = {
>
> typedef int (*cppc_mode_transition_fn)(int);
>
> +static struct quirk_entry quirk_amd_7k62 = {
> + .nominal_freq = 2600,
> + .lowest_freq = 550,
> +};
> +
> +static int __init dmi_matched(const struct dmi_system_id *dmi)
> +{
> + quirks = dmi->driver_data; > +

Under the presumption that the quirk list will grow as more buggy older
machines are identified, maybe it's worth having a dyndbg or info
statement here to indicate that it's using quirked values for dmi->ident.

> + return 1;
> +}
> +
> +static const struct dmi_system_id amd_pstate_quirks_table[] __initconst = {
> + {
> + .callback = dmi_matched,
> + .ident = "AMD EPYC 7K62",
> + .matches = {
> + DMI_MATCH(DMI_PRODUCT_VERSION, "C1"),
> + DMI_MATCH(DMI_PRODUCT_SERIAL, "FX19911000028"),

This is way too specific isn't it? It would only load on that single
system I would expect. But I think you want to have an entry that
matches the DMI_PRODUCT_NAME or DMI_FAMILY_NAME instead most likely.

> + },
> + .driver_data = &quirk_amd_7k62,
> + },
> + {}
> +};
> +MODULE_DEVICE_TABLE(dmi, amd_pstate_quirks_table);
> +
> static inline int get_mode_idx_from_str(const char *str, size_t size)
> {
> int i;
> @@ -581,13 +608,19 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
> static int amd_get_min_freq(struct amd_cpudata *cpudata)
> {
> struct cppc_perf_caps cppc_perf;
> + u32 lowest_freq;
>
> int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
> if (ret)
> return ret;
>
> + if (quirks && quirks->lowest_freq)
> + lowest_freq = quirks->lowest_freq;
> + else
> + lowest_freq = cppc_perf.lowest_freq;
> +
> /* Switch to khz */
> - return cppc_perf.lowest_freq * 1000;
> + return lowest_freq * 1000;
> }
>
> static int amd_get_max_freq(struct amd_cpudata *cpudata)
> @@ -619,13 +652,14 @@ static int amd_get_max_freq(struct amd_cpudata *cpudata)
>
> static int amd_get_nominal_freq(struct amd_cpudata *cpudata)
> {
> - struct cppc_perf_caps cppc_perf;
> + u32 nominal_freq;
>
> - int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
> - if (ret)
> - return ret;

I think this hunk should be earlier in your series. Conceptually it
seems to match what patch 3 does to me.

> + if (quirks && quirks->nominal_freq)
> + nominal_freq = quirks->nominal_freq;
> + else
> + nominal_freq = READ_ONCE(cpudata->nominal_freq);
>
> - return cppc_perf.nominal_freq;
> + return nominal_freq;
> }
>
> static int amd_get_lowest_nonlinear_freq(struct amd_cpudata *cpudata)
> @@ -1623,6 +1657,11 @@ static int __init amd_pstate_init(void)
> if (cpufreq_get_current_driver())
> return -EEXIST;
>
> + quirks = NULL;
> +
> + /* check if this machine need CPPC quirks */
> + dmi_check_system(amd_pstate_quirks_table);
> +
> switch (cppc_state) {
> case AMD_PSTATE_UNDEFINED:
> /* Disable on the following configs by default:
> diff --git a/include/linux/amd-pstate.h b/include/linux/amd-pstate.h
> index 446394f84606..ea80f961607d 100644
> --- a/include/linux/amd-pstate.h
> +++ b/include/linux/amd-pstate.h
> @@ -110,4 +110,10 @@ static const char * const amd_pstate_mode_string[] = {
> [AMD_PSTATE_GUIDED] = "guided",
> NULL,
> };
> +
> +struct quirk_entry {
> + u32 nominal_freq;
> + u32 lowest_freq;
> +};
> +
> #endif /* _LINUX_AMD_PSTATE_H */


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