From: Henry Tseng Date: Tue, 24 Mar 2026 09:09:48 +0000 (+0800) Subject: cpufreq: acpi-cpufreq: use DMI max speed when CPPC is unavailable X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=16fb8d8a0e050e8f151da7dd2e03ccc500dfd8da;p=thirdparty%2Fkernel%2Flinux.git 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 Link: https://patch.msgid.link/20260324090948.1667340-1-henrytseng@qnap.com Signed-off-by: Rafael J. Wysocki --- diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index f0e513e9ed5d3..f53de414acf20 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 diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c index e7eff6c2f0925..21639d9ac753b 100644 --- a/drivers/cpufreq/acpi-cpufreq.c +++ b/drivers/cpufreq/acpi-cpufreq.c @@ -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; diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h index 4d644f03098e3..e6c5ef3173c52 100644 --- a/include/acpi/cppc_acpi.h +++ b/include/acpi/cppc_acpi.h @@ -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);