From: Wyes Karny wyes.karny@amd.com
MSR_AMD_PERF_CTL is guaranteed to be 0 on a cold boot. However, on a kexec boot, for instance, it may have a non-zero value (if the cpu was in a non-P0 Pstate). In such cases, the cores with non-P0 Pstates at boot will never be pushed to P0, let alone boost frequencies.
Kexec is a common workflow for reboot on Linux and this creates a regression in performance. Fix it by explicitly setting the MSR_AMD_PERF_CTL to 0 during amd_pstate driver init.
Cc: stable@vger.kernel.org Reviewed-by: Gautham R. Shenoy gautham.shenoy@amd.com Tested-by: Wyes Karny wyes.karny@amd.com Signed-off-by: Wyes Karny wyes.karny@amd.com Signed-off-by: Perry Yuan Perry.Yuan@amd.com --- drivers/cpufreq/amd-pstate.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index ace7d50cf2ac..d844c6f97caf 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -424,12 +424,22 @@ static void amd_pstate_boost_init(struct amd_cpudata *cpudata) amd_pstate_driver.boost_enabled = true; }
+static void amd_perf_ctl_reset(unsigned int cpu) +{ + wrmsrl_on_cpu(cpu, MSR_AMD_PERF_CTL, 0); +} + static int amd_pstate_cpu_init(struct cpufreq_policy *policy) { int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret; struct device *dev; struct amd_cpudata *cpudata;
+ /* + * Resetting PERF_CTL_MSR will put the CPU in P0 frequency, + * which is ideal for initialization process. + */ + amd_perf_ctl_reset(policy->cpu); dev = get_cpu_device(policy->cpu); if (!dev) return -ENODEV;