[PATCH 05/19] cpufreq: amd: add fast switch function for amd-pstate module

Huang Rui
2021-09-08T15:01:38Z

Introduce the fast switch function for amd-pstate module on the AMD
processors which support the full MSR register control. It's able to
decrease the lattency on interrupt context.

Signed-off-by: Huang Rui <ray.huang@amd.com>
---
drivers/cpufreq/amd-pstate.c | 64 ++++++++++++++++++++++++++++++++++++
1 file changed, 64 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 4c9c9bf1d72b..32b4f6d79783 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -212,6 +212,66 @@ static int amd_pstate_target(struct cpufreq_policy *policy,
return ret;
}

+static void amd_pstate_adjust_perf(unsigned int cpu,
+ unsigned long min_perf,
+ unsigned long target_perf,
+ unsigned long capacity)
+{
+ unsigned long amd_max_perf, amd_min_perf, amd_des_perf,
+ amd_cap_perf, lowest_nonlinear_perf;
+ struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+ struct amd_cpudata *cpudata = policy->driver_data;
+
+ amd_cap_perf = READ_ONCE(cpudata->highest_perf);
+ lowest_nonlinear_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);
+
+ if (target_perf < capacity)
+ amd_des_perf = DIV_ROUND_UP(amd_cap_perf * target_perf,
+ capacity);
+
+ amd_min_perf = READ_ONCE(cpudata->highest_perf);
+ if (min_perf < capacity)
+ amd_min_perf = DIV_ROUND_UP(amd_cap_perf * min_perf, capacity);
+
+ if (amd_min_perf < lowest_nonlinear_perf)
+ amd_min_perf = lowest_nonlinear_perf;
+
+ amd_max_perf = amd_cap_perf;
+ if (amd_max_perf < amd_min_perf)
+ amd_max_perf = amd_min_perf;
+
+ amd_des_perf = clamp_t(unsigned long, amd_des_perf,
+ amd_min_perf, amd_max_perf);
+
+ amd_pstate_update(cpudata, amd_min_perf, amd_des_perf,
+ amd_max_perf, true);
+}
+
+static unsigned int amd_pstate_fast_switch(struct cpufreq_policy *policy,
+ unsigned int target_freq)
+{
+ u64 ratio;
+ struct amd_cpudata *cpudata = policy->driver_data;
+ unsigned long amd_max_perf, amd_min_perf, amd_des_perf, nominal_perf;
+
+ if (!cpudata->max_freq)
+ return -ENODEV;
+
+ amd_max_perf = READ_ONCE(cpudata->highest_perf);
+ amd_min_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);
+
+ amd_des_perf = DIV_ROUND_UP(target_freq * amd_max_perf,
+ cpudata->max_freq);
+
+ amd_pstate_update(cpudata, amd_min_perf, amd_des_perf,
+ amd_max_perf, true);
+
+ nominal_perf = READ_ONCE(cpudata->nominal_perf);
+ ratio = div_u64(amd_des_perf << SCHED_CAPACITY_SHIFT, nominal_perf);
+
+ return cpudata->nominal_freq * ratio >> SCHED_CAPACITY_SHIFT;
+}
+
static int amd_get_min_freq(struct amd_cpudata *cpudata)
{
struct cppc_perf_caps cppc_perf;
@@ -356,6 +416,8 @@ 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) {
@@ -408,6 +470,8 @@ static struct cpufreq_driver amd_pstate_driver = {
.flags = CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
.verify = amd_pstate_verify,
.target = amd_pstate_target,
+ .fast_switch = amd_pstate_fast_switch,
+ .adjust_perf = amd_pstate_adjust_perf,
.init = amd_pstate_cpu_init,
.exit = amd_pstate_cpu_exit,
.name = "amd-pstate",
--
2.25.1