linux-kernel - [PATCH v2 6/9] cpufreq: amd_pstate: add AMD pstate EPP support for shared memory type processor

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Date:   Sun, 9 Oct 2022 15:10:30 +0800
From:   Perry Yuan <Perry.Yuan@....com>
To:     <rafael.j.wysocki@...el.com>, <ray.huang@....com>,
        <viresh.kumar@...aro.org>
CC:     <Deepak.Sharma@....com>, <Mario.Limonciello@....com>,
        <Nathan.Fontenot@....com>, <Alexander.Deucher@....com>,
        <Shimmer.Huang@....com>, <Xiaojian.Du@....com>, <Li.Meng@....com>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Perry Yuan <Perry.Yuan@....com>
Subject: [PATCH v2 6/9] cpufreq: amd_pstate: add AMD pstate EPP support for shared memory type processor

Add Energy Performance Preference support for AMD SOCs which do not
contain a designated MSR for CPPC support. A shared memory interface
is used for CPPC on these SOCs and the ACPI PCC channel is used to
enable EPP and reset the desired performance.

Signed-off-by: Perry Yuan <Perry.Yuan@....com>
---
 drivers/cpufreq/amd-pstate.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 14a275c22aff..4c24fe391a55 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -135,12 +135,25 @@ static inline int pstate_enable(bool enable)
 
 static int cppc_enable(bool enable)
 {
+	struct cppc_perf_ctrls perf_ctrls;
 	int cpu, ret = 0;
 
 	for_each_present_cpu(cpu) {
 		ret = cppc_set_enable(cpu, enable);
 		if (ret)
 			return ret;
+		if (epp_enabled) {
+			/* Enable autonomous mode for EPP */
+			ret = cppc_set_auto_epp(cpu, enable);
+			if (ret)
+				return ret;
+
+			/* Set desired perf as zero to allow EPP firmware control */
+			perf_ctrls.desired_perf = 0;
+			ret = cppc_set_perf(cpu, &perf_ctrls);
+			if (ret)
+				return ret;
+		}
 	}
 
 	return ret;
-- 
2.34.1