From f965d111e68f4a993cc44d487d416e3d954eea11 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Fri, 26 Sep 2025 12:19:41 +0200 Subject: cpufreq: CPPC: Avoid using CPUFREQ_ETERNAL as transition delay If cppc_get_transition_latency() returns CPUFREQ_ETERNAL to indicate a failure to retrieve the transition latency value from the platform firmware, the CPPC cpufreq driver will use that value (converted to microseconds) as the policy transition delay, but it is way too large for any practical use. Address this by making the driver use the cpufreq's default transition latency value (in microseconds) as the transition delay if CPUFREQ_ETERNAL is returned by cppc_get_transition_latency(). Fixes: d4f3388afd48 ("cpufreq / CPPC: Set platform specific transition_delay_us") Cc: 5.19+ # 5.19 Signed-off-by: Rafael J. Wysocki Reviewed-by: Mario Limonciello (AMD) Reviewed-by: Jie Zhan Acked-by: Viresh Kumar Reviewed-by: Qais Yousef --- drivers/cpufreq/cppc_cpufreq.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'drivers/cpufreq/cppc_cpufreq.c') diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index 12de0ac7bbaf..b71946937c52 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -308,6 +308,16 @@ static int cppc_verify_policy(struct cpufreq_policy_data *policy) return 0; } +static unsigned int __cppc_cpufreq_get_transition_delay_us(unsigned int cpu) +{ + unsigned int transition_latency_ns = cppc_get_transition_latency(cpu); + + if (transition_latency_ns == CPUFREQ_ETERNAL) + return CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS / NSEC_PER_USEC; + + return transition_latency_ns / NSEC_PER_USEC; +} + /* * The PCC subspace describes the rate at which platform can accept commands * on the shared PCC channel (including READs which do not count towards freq @@ -330,12 +340,12 @@ static unsigned int cppc_cpufreq_get_transition_delay_us(unsigned int cpu) return 10000; } } - return cppc_get_transition_latency(cpu) / NSEC_PER_USEC; + return __cppc_cpufreq_get_transition_delay_us(cpu); } #else static unsigned int cppc_cpufreq_get_transition_delay_us(unsigned int cpu) { - return cppc_get_transition_latency(cpu) / NSEC_PER_USEC; + return __cppc_cpufreq_get_transition_delay_us(cpu); } #endif -- cgit v1.2.3 From c28a280bd465690981099cd6e43dfcfa5c28b133 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Fri, 26 Sep 2025 12:29:50 +0200 Subject: ACPI: CPPC: Do not use CPUFREQ_ETERNAL as an error value Instead of using CPUFREQ_ETERNAL for signaling an error condition in cppc_get_transition_latency(), change the return value type of that function to int and make it return a proper negative error code on failures. No intentional functional impact. Reviewed-by: Mario Limonciello (AMD) Reviewed-by: Jie Zhan Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar Reviewed-by: Qais Yousef --- drivers/acpi/cppc_acpi.c | 16 +++++++--------- drivers/cpufreq/amd-pstate.c | 8 ++++---- drivers/cpufreq/cppc_cpufreq.c | 4 ++-- include/acpi/cppc_acpi.h | 6 +++--- 4 files changed, 16 insertions(+), 18 deletions(-) (limited to 'drivers/cpufreq/cppc_cpufreq.c') diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 6b649031808f..ab4651205e8a 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -1876,7 +1876,7 @@ EXPORT_SYMBOL_GPL(cppc_set_perf); * If desired_reg is in the SystemMemory or SystemIo ACPI address space, * then assume there is no latency. */ -unsigned int cppc_get_transition_latency(int cpu_num) +int cppc_get_transition_latency(int cpu_num) { /* * Expected transition latency is based on the PCCT timing values @@ -1889,31 +1889,29 @@ unsigned int cppc_get_transition_latency(int cpu_num) * completion of a command before issuing the next command, * in microseconds. */ - unsigned int latency_ns = 0; struct cpc_desc *cpc_desc; struct cpc_register_resource *desired_reg; int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu_num); struct cppc_pcc_data *pcc_ss_data; + int latency_ns = 0; cpc_desc = per_cpu(cpc_desc_ptr, cpu_num); if (!cpc_desc) - return CPUFREQ_ETERNAL; + return -ENODATA; desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF]; if (CPC_IN_SYSTEM_MEMORY(desired_reg) || CPC_IN_SYSTEM_IO(desired_reg)) return 0; - else if (!CPC_IN_PCC(desired_reg)) - return CPUFREQ_ETERNAL; - if (pcc_ss_id < 0) - return CPUFREQ_ETERNAL; + if (!CPC_IN_PCC(desired_reg) || pcc_ss_id < 0) + return -ENODATA; pcc_ss_data = pcc_data[pcc_ss_id]; if (pcc_ss_data->pcc_mpar) latency_ns = 60 * (1000 * 1000 * 1000 / pcc_ss_data->pcc_mpar); - latency_ns = max(latency_ns, pcc_ss_data->pcc_nominal * 1000); - latency_ns = max(latency_ns, pcc_ss_data->pcc_mrtt * 1000); + latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_nominal * 1000); + latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_mrtt * 1000); return latency_ns; } diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index b4c79fde1979..298e92d8cc03 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -872,10 +872,10 @@ static void amd_pstate_update_limits(struct cpufreq_policy *policy) */ static u32 amd_pstate_get_transition_delay_us(unsigned int cpu) { - u32 transition_delay_ns; + int transition_delay_ns; transition_delay_ns = cppc_get_transition_latency(cpu); - if (transition_delay_ns == CPUFREQ_ETERNAL) { + if (transition_delay_ns < 0) { if (cpu_feature_enabled(X86_FEATURE_AMD_FAST_CPPC)) return AMD_PSTATE_FAST_CPPC_TRANSITION_DELAY; else @@ -891,10 +891,10 @@ static u32 amd_pstate_get_transition_delay_us(unsigned int cpu) */ static u32 amd_pstate_get_transition_latency(unsigned int cpu) { - u32 transition_latency; + int transition_latency; transition_latency = cppc_get_transition_latency(cpu); - if (transition_latency == CPUFREQ_ETERNAL) + if (transition_latency < 0) return AMD_PSTATE_TRANSITION_LATENCY; return transition_latency; diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index b71946937c52..e23d9abea135 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -310,9 +310,9 @@ static int cppc_verify_policy(struct cpufreq_policy_data *policy) static unsigned int __cppc_cpufreq_get_transition_delay_us(unsigned int cpu) { - unsigned int transition_latency_ns = cppc_get_transition_latency(cpu); + int transition_latency_ns = cppc_get_transition_latency(cpu); - if (transition_latency_ns == CPUFREQ_ETERNAL) + if (transition_latency_ns < 0) return CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS / NSEC_PER_USEC; return transition_latency_ns / NSEC_PER_USEC; diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h index 20f3d62e7a16..13fa81504844 100644 --- a/include/acpi/cppc_acpi.h +++ b/include/acpi/cppc_acpi.h @@ -160,7 +160,7 @@ extern unsigned int cppc_khz_to_perf(struct cppc_perf_caps *caps, unsigned int f extern bool acpi_cpc_valid(void); extern bool cppc_allow_fast_switch(void); extern int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data); -extern unsigned int cppc_get_transition_latency(int cpu); +extern int cppc_get_transition_latency(int cpu); extern bool cpc_ffh_supported(void); extern bool cpc_supported_by_cpu(void); extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val); @@ -216,9 +216,9 @@ static inline bool cppc_allow_fast_switch(void) { return false; } -static inline unsigned int cppc_get_transition_latency(int cpu) +static inline int cppc_get_transition_latency(int cpu) { - return CPUFREQ_ETERNAL; + return -ENODATA; } static inline bool cpc_ffh_supported(void) { -- cgit v1.2.3