5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com
[ Upstream commit f965d111e68f4a993cc44d487d416e3d954eea11 ]
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+ stable@vger.kernel.org # 5.19 Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Mario Limonciello (AMD) superm1@kernel.org Reviewed-by: Jie Zhan zhanjie9@hisilicon.com Acked-by: Viresh Kumar viresh.kumar@linaro.org Reviewed-by: Qais Yousef qyousef@layalina.io [ added CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS definition to include/linux/cpufreq.h ] Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/cpufreq/cppc_cpufreq.c | 14 ++++++++++++-- include/linux/cpufreq.h | 3 +++ 2 files changed, 15 insertions(+), 2 deletions(-)
--- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -395,6 +395,16 @@ static int cppc_verify_policy(struct cpu 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 @@ -417,14 +427,14 @@ static unsigned int cppc_cpufreq_get_tra 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
--- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -32,6 +32,9 @@ */
#define CPUFREQ_ETERNAL (-1) + +#define CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS NSEC_PER_MSEC + #define CPUFREQ_NAME_LEN 16 /* Print length for names. Extra 1 space for accommodating '\n' in prints */ #define CPUFREQ_NAME_PLEN (CPUFREQ_NAME_LEN + 1)