linux-kernel - [PATCH] cpufreq/amd-pstate: Fix amd_pstate mode switch on shared memory systems

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Message-ID: <20241004122303.94283-1-Dhananjay.Ugwekar@amd.com>
Date: Fri, 4 Oct 2024 12:23:04 +0000
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: <gautham.shenoy@....com>, <mario.limonciello@....com>,
	<perry.yuan@....com>, <ray.huang@....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] cpufreq/amd-pstate: Fix amd_pstate mode switch on shared memory systems

While switching the driver mode between active and passive, Collaborative
Processor Performance Control (CPPC) is disabled in
amd_pstate_unregister_driver(). But, it is not enabled back while registering
the new driver (passive or active). This leads to the new driver mode not
working correctly, so enable it back in amd_pstate_register_driver().

Fixes: 3ca7bc818d8c ("cpufreq: amd-pstate: Add guided mode control support via sysfs")
Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
---
 drivers/cpufreq/amd-pstate.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index cdc08d2ddd52..4acf5fbeb116 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1191,11 +1191,21 @@ static int amd_pstate_register_driver(int mode)
 		return -EINVAL;
 
 	cppc_state = mode;
+
+	ret = amd_pstate_enable(true);
+	if (ret) {
+		pr_err("failed to enable cppc during amd-pstate driver registration, return %d\n",
+		       ret);
+		amd_pstate_driver_cleanup();
+		return ret;
+	}
+
 	ret = cpufreq_register_driver(current_pstate_driver);
 	if (ret) {
 		amd_pstate_driver_cleanup();
 		return ret;
 	}
+
 	return 0;
 }
 
-- 
2.34.1