Commit 1d215f03 authored by Huang Rui's avatar Huang Rui Committed by Rafael J. Wysocki
Browse files

cpufreq: amd-pstate: Add fast switch function for AMD P-State 



Introduce the fast switch function for AMD P-State on the AMD processors
which support the full MSR register control. It's able to decrease the
latency on interrupt context.

Signed-off-by: default avatarHuang Rui <ray.huang@amd.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent ec437d71

drivers/cpufreq/amd-pstate.c

+36 −0
Original line number Diff line number Diff line
@@ -183,6 +183,39 @@ static int amd_pstate_target(struct cpufreq_policy *policy, 
	return 0;

}



static void amd_pstate_adjust_perf(unsigned int cpu,

				   unsigned long _min_perf,

				   unsigned long target_perf,

				   unsigned long capacity)

{

	unsigned long max_perf, min_perf, des_perf,

		      cap_perf, lowest_nonlinear_perf;

	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);

	struct amd_cpudata *cpudata = policy->driver_data;



	cap_perf = READ_ONCE(cpudata->highest_perf);

	lowest_nonlinear_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);



	des_perf = cap_perf;

	if (target_perf < capacity)

		des_perf = DIV_ROUND_UP(cap_perf * target_perf, capacity);



	min_perf = READ_ONCE(cpudata->highest_perf);

	if (_min_perf < capacity)

		min_perf = DIV_ROUND_UP(cap_perf * _min_perf, capacity);



	if (min_perf < lowest_nonlinear_perf)

		min_perf = lowest_nonlinear_perf;



	max_perf = cap_perf;

	if (max_perf < min_perf)

		max_perf = min_perf;



	des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf);



	amd_pstate_update(cpudata, min_perf, des_perf, max_perf, true);

}



static int amd_get_min_freq(struct amd_cpudata *cpudata)

{

	struct cppc_perf_caps cppc_perf;
@@ -299,6 +332,8 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy) 
	/* It will be updated by governor */

	policy->cur = policy->cpuinfo.min_freq;



	policy->fast_switch_possible = true;



	/* Initial processor data capability frequencies */

	cpudata->max_freq = max_freq;

	cpudata->min_freq = min_freq;
@@ -329,6 +364,7 @@ static struct cpufreq_driver amd_pstate_driver = { 
	.flags		= CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,

	.verify		= amd_pstate_verify,

	.target		= amd_pstate_target,

	.adjust_perf    = amd_pstate_adjust_perf,

	.init		= amd_pstate_cpu_init,

	.exit		= amd_pstate_cpu_exit,

	.name		= "amd-pstate",