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>
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