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Subject[PATCH v5 07/22] cpufreq: amd: add fast switch function for amd-pstate
Date
Introduce the fast switch function for amd-pstate 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>
---
drivers/cpufreq/amd-pstate.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 20ffbc30118f..cab266b8bf35 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -177,6 +177,39 @@ 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;
@@ -293,6 +326,8 @@ 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;
+
ret = freq_qos_add_request(&policy->constraints, &cpudata->req[0],
FREQ_QOS_MIN, policy->cpuinfo.min_freq);
if (ret < 0) {
@@ -341,6 +376,7 @@ 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",
--
2.25.1
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