Commit 919f4557 authored by Wyes Karny's avatar Wyes Karny Committed by Rafael J. Wysocki
Browse files

cpufreq: amd-pstate: cpufreq: amd-pstate: reset MSR_AMD_PERF_CTL register at init 



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: All applicable <stable@vger.kernel.org>
Acked-by: default avatarHuang Rui <ray.huang@amd.com>
Reviewed-by: default avatarGautham R. Shenoy <gautham.shenoy@amd.com>
Tested-by: default avatarWyes Karny <wyes.karny@amd.com>
Signed-off-by: default avatarWyes Karny <wyes.karny@amd.com>
Signed-off-by: default avatarPerry Yuan <Perry.Yuan@amd.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent cdcc5ef2

drivers/cpufreq/amd-pstate.c

+10 −0
Original line number Diff line number Diff line
@@ -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;