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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: Huang Rui <ray.huang@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Huang Rui 2021-12-24 09:05:01 +08:00 committed by Rafael J. Wysocki
parent ec437d71db
commit 1d215f0319
1 changed files with 36 additions and 0 deletions
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36
drivers/cpufreq/amd-pstate.c
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@ -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",