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cpufreq: acpi-cpufreq: use DMI max speed when CPPC is unavailable 

On AMD Ryzen Embedded V1780B (Family 17h, Zen 1), the BIOS does not
provide ACPI _CPC objects and the CPU does not support MSR-based CPPC
(X86_FEATURE_CPPC).  The _PSS table only lists nominal P-states
(P0 = 3350 MHz), so when get_max_boost_ratio() fails at
cppc_get_perf_caps(), cpuinfo_max_freq reports only the base frequency
instead of the rated boost frequency (3600 MHz).

  dmesg:
    ACPI CPPC: No CPC descriptor for CPU:0
    acpi_cpufreq: CPU0: Unable to get performance capabilities (-19)

cppc-cpufreq already has a DMI fallback (cppc_get_dmi_max_khz()) that
reads the processor max speed from SMBIOS Type 4.  Export it and reuse
it in acpi-cpufreq as a last-resort source for the boost frequency.

A sanity check ensures the DMI value is above the _PSS P0 frequency
and within 2x of it; values outside that range are ignored and the
existing arch_set_max_freq_ratio() path is taken instead.  The 2x
upper bound is based on a survey of the AMD Ryzen Embedded V1000
series, where the highest boost-to-base ratio is 1.8x (V1404I:
2.0 GHz base / 3.6 GHz boost).

The DMI lookup and sanity check are wrapped in a helper,
acpi_cpufreq_resolve_max_freq(), which falls through to
arch_set_max_freq_ratio() if the DMI value is absent or
out of range.

Tested on AMD Ryzen Embedded V1780B with v7.0-rc4:

  Before: cpuinfo_max_freq = 3350000 (base only)
  After:  cpuinfo_max_freq = 3600000 (includes boost)

Link: https://www.amd.com/en/products/embedded/ryzen/ryzen-v1000-series.html#specifications
Signed-off-by: Henry Tseng <henrytseng@qnap.com>
Link: https://patch.msgid.link/20260324090948.1667340-1-henrytseng@qnap.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Henry Tseng 2026-03-24 17:09:48 +08:00 committed by Rafael J. Wysocki
parent 16c1e8385b
commit 16fb8d8a0e
3 changed files with 27 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/acpi/cppc_acpi.c
View File

@ -1944,7 +1944,7 @@ static void cppc_find_dmi_mhz(const struct dmi_header *dm, void *private)
}
/* Look up the max frequency in DMI */
static u64 cppc_get_dmi_max_khz(void)
u64 cppc_get_dmi_max_khz(void)
{
u16 mhz = 0;
@ -1958,6 +1958,7 @@ static u64 cppc_get_dmi_max_khz(void)
return KHZ_PER_MHZ * mhz;
}
EXPORT_SYMBOL_GPL(cppc_get_dmi_max_khz);
/*
* If CPPC lowest_freq and nominal_freq registers are exposed then we can

31
drivers/cpufreq/acpi-cpufreq.c
View File

@ -675,6 +675,29 @@ static inline u64 get_max_boost_ratio(unsigned int cpu, u64 *nominal_freq)
}
#endif
static void acpi_cpufreq_resolve_max_freq(struct cpufreq_policy *policy,
unsigned int pss_max_freq)
{
#ifdef CONFIG_ACPI_CPPC_LIB
u64 max_speed = cppc_get_dmi_max_khz();
/*
* Use DMI "Max Speed" if it looks plausible: must be
* above _PSS P0 frequency and within 2x of it.
*/
if (max_speed > pss_max_freq && max_speed < pss_max_freq * 2) {
policy->cpuinfo.max_freq = max_speed;
return;
}
#endif
/*
* If the maximum "boost" frequency is unknown, ask the arch
* scale-invariance code to use the "nominal" performance for
* CPU utilization scaling so as to prevent the schedutil
* governor from selecting inadequate CPU frequencies.
*/
arch_set_max_freq_ratio(true);
}
static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
struct cpufreq_frequency_table *freq_table;
@ -849,13 +872,7 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
policy->cpuinfo.max_freq = freq * max_boost_ratio >> SCHED_CAPACITY_SHIFT;
} else {
/*
* If the maximum "boost" frequency is unknown, ask the arch
* scale-invariance code to use the "nominal" performance for
* CPU utilization scaling so as to prevent the schedutil
* governor from selecting inadequate CPU frequencies.
*/
arch_set_max_freq_ratio(true);
acpi_cpufreq_resolve_max_freq(policy, freq_table[0].frequency);
}
policy->freq_table = freq_table;

1
include/acpi/cppc_acpi.h
View File

@ -156,6 +156,7 @@ extern int cppc_set_enable(int cpu, bool enable);
extern int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps);
extern bool cppc_perf_ctrs_in_pcc_cpu(unsigned int cpu);
extern bool cppc_perf_ctrs_in_pcc(void);
extern u64 cppc_get_dmi_max_khz(void);
extern unsigned int cppc_perf_to_khz(struct cppc_perf_caps *caps, unsigned int perf);
extern unsigned int cppc_khz_to_perf(struct cppc_perf_caps *caps, unsigned int freq);
extern bool acpi_cpc_valid(void);