linux-kernel - [PATCH 2/4] cpufreq/amd-pstate: Do not attempt to clear MSR_AMD_CPPC

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Message-ID: <20241023102108.5980-3-Dhananjay.Ugwekar@amd.com>
Date: Wed, 23 Oct 2024 10:21:08 +0000
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: <gautham.shenoy@....com>, <mario.limonciello@....com>,
	<perry.yuan@....com>, <rafael@...nel.org>, <viresh.kumar@...aro.org>
CC: <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Dhananjay
 Ugwekar" <Dhananjay.Ugwekar@....com>
Subject: [PATCH 2/4] cpufreq/amd-pstate: Do not attempt to clear MSR_AMD_CPPC_ENABLE

MSR_AMD_CPPC_ENABLE is a write once register, i.e. attempting to clear
it is futile, it will not take effect. Hence, return if disable (0)
argument is passed to the msr_cppc_enable()

Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
---
 drivers/cpufreq/amd-pstate.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 0b4a4d69c14d..576251e61ce0 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -311,6 +311,12 @@ static inline int msr_cppc_enable(bool enable)
 	int ret, cpu;
 	unsigned long logical_proc_id_mask = 0;
 
+       /*
+        * MSR_AMD_CPPC_ENABLE is write-once, once set it cannot be cleared.
+        */
+	if (!enable)
+		return 0;
+
 	if (enable == cppc_enabled)
 		return 0;
 
-- 
2.34.1