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>

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 2698ed5ec6d7a37e52cdb19acf62a92bbfdc13c6..8c9c199b560ef8b6913448c6059355b2bfacf6cf 100644 (file)
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -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",