linux-kernel - [RFC PATCH 6.1.y 1/1] cpufreq: amd-pstate: Enable CPU boost in passive and guided modes

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Message-Id: <20241025010527.491605-2-dev@nalramli.com>
Date: Thu, 24 Oct 2024 21:05:27 -0400
From: "Nabil S. Alramli" <dev@...ramli.com>
To: stable@...r.kernel.org
Cc: nalramli@...tly.com,
	jdamato@...tly.com,
	khubert@...tly.com,
	Perry.Yuan@....com,
	li.meng@....com,
	ray.huang@....com,
	rafael@...nel.org,
	viresh.kumar@...aro.org,
	linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Nabil S. Alramli" <dev@...ramli.com>
Subject: [RFC PATCH 6.1.y 1/1] cpufreq: amd-pstate: Enable CPU boost in passive and guided modes

The CPU frequency cannot be boosted when using the amd_pstate driver in
passive or guided mode. This is fixed here.

The CPU frequency is dependent on a setting called highest_perf which is
the multiplier used to compute it. The highest_perf value comes from
cppc_init_perf when the driver is built-in and from pstate_init_perf when
it is a loaded module. Both of these calls have the following condition:

	highest_perf = amd_get_highest_perf();
	if (highest_perf > __cppc_highest_perf_)
		highest_perf = __cppc_highest_perf;

Where again __cppc_highest_perf is either the return from
cppc_get_perf_caps in the built-in case or AMD_CPPC_HIGHEST_PERF in the
module case. Both of these functions actually return the nominal value,
Whereas the call to amd_get_highest_perf returns the correct boost value,
so the condition tests true and highest_perf always ends up being the
nominal value, therefore never having the ability to boost CPU frequency.

Since amd_get_highest_perf already returns the boost value we should just
eliminate this check.

Signed-off-by: Nabil S. Alramli <dev@...ramli.com>
Fixes: bedadcfb011f ("cpufreq: amd-pstate: Fix initial highest_perf value")
See-also: 1ec40a175a48 ("cpufreq: amd-pstate: Enable amd-pstate preferred core support")
Cc: Perry.Yuan@....com
Cc: li.meng@....com
Cc: stable@...r.kernel.org # 6.1 - v6.6.50
---
 drivers/cpufreq/amd-pstate.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 90dcf26f0973..c66086ae624a 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -102,9 +102,7 @@ static int pstate_init_perf(struct amd_cpudata *cpudata)
 	 *
 	 * CPPC entry doesn't indicate the highest performance in some ASICs.
 	 */
-	highest_perf = amd_get_highest_perf();
-	if (highest_perf > AMD_CPPC_HIGHEST_PERF(cap1))
-		highest_perf = AMD_CPPC_HIGHEST_PERF(cap1);
+	highest_perf = max(amd_get_highest_perf(), AMD_CPPC_HIGHEST_PERF(cap1));

 	WRITE_ONCE(cpudata->highest_perf, highest_perf);

@@ -124,9 +122,7 @@ static int cppc_init_perf(struct amd_cpudata *cpudata)
 	if (ret)
 		return ret;

-	highest_perf = amd_get_highest_perf();
-	if (highest_perf > cppc_perf.highest_perf)
-		highest_perf = cppc_perf.highest_perf;
+	highest_perf = max(amd_get_highest_perf(), cppc_perf.highest_perf);

 	WRITE_ONCE(cpudata->highest_perf, highest_perf);

-- 
2.35.1