diff options
| author | Henry Tseng <henrytseng@qnap.com> | 2026-03-24 17:09:48 +0800 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2026-03-25 14:29:05 +0100 |
| commit | 16fb8d8a0e050e8f151da7dd2e03ccc500dfd8da (patch) | |
| tree | f50dd2b0604c008dbb4e3f599e9a354a20c7e0c3 /drivers/acpi | |
| parent | 16c1e8385b3bb65d412d7a60107f8894587c63fa (diff) | |
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>
Diffstat (limited to 'drivers/acpi')
| -rw-r--r-- | drivers/acpi/cppc_acpi.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index f0e513e9ed5d..f53de414acf2 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -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 |