linux-kernel - [PATCH v7 07/14] cpufreq: amd-pstate: Add fast switch function for AMD P-State

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Date:   Fri, 24 Dec 2021 09:05:01 +0800
From:   Huang Rui <ray.huang@....com>
To:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        "Borislav Petkov" <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Steven Rostedt <rostedt@...dmis.org>,
        <linux-pm@...r.kernel.org>
CC:     Deepak Sharma <deepak.sharma@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        Steven Noonan <steven@...vesoftware.com>,
        Nathan Fontenot <nathan.fontenot@....com>,
        Jinzhou Su <Jinzhou.Su@....com>,
        Xiaojian Du <Xiaojian.Du@....com>,
        <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        Huang Rui <ray.huang@....com>
Subject: [PATCH v7 07/14] 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@....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 2698ed5ec6d7..8c9c199b560e 100644
--- 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",
-- 
2.25.1