cpufreq: CPPC: Avoid using CPUFREQ_ETERNAL as transition delay

[ 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>

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index b7294531816bedf4a91fe871250e4603014678c6..b72fd4ff2cdace8effc9370ba4fcd4a889da7584 100644 (file)
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -395,6 +395,16 @@ 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
@@ -417,14 +427,14 @@ 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
 

diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 025391be1b19914734fed8a5ecf5649bd88f8957..8e3a1d4e0a3a23b52e90f512ebf4a715471a977c 100644 (file)
--- 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)