From: Wyes Karny <wyes.karny@xxxxxxx>
MSR_AMD_PERF_CTL register should be reseted while initializing the
amd_pstate driver. On a running system, if we switch the cpufreq driver
from acpi_cpufreq to amd_pstate, we see the following issue: There is no
frequency change on cores which were previously running at a non-zero
pstate. Hence, reset the pstate to zero on all the cores during the
initialization of the amd_pstate driver to avoid performance drop.
While the AMD_PERF_CTL MSR is guaranteed to be set to 0 on a cold boot,
the same is not true for a kexec boot, which is a very common mode of
switching kernels/reboot in MDCs and Ubuntu.
Signed-off-by: Wyes Karny <wyes.karny@xxxxxxx>
Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/cpufreq/amd-pstate.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 1ffb97b6dbe2..0057ad5dfa97 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -420,12 +420,18 @@ 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;
+ amd_perf_ctl_reset(policy->cpu);
dev = get_cpu_device(policy->cpu);
if (!dev)
return -ENODEV;
--
2.25.1
