[Bug 221505] REGRESSION][amd_pstate] "EPP cannot be set under performance policy" (EBUSY) when switching to performance profile via PPD on 7.1

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=221505

Marco Scardovi (scardracs@disroot.org) changed:

           What    |Removed                     |Added
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                 CC|                            |scardracs@disroot.org

--- Comment #28 from Marco Scardovi (scardracs@disroot.org) ---
@Mario I took a look into it and made a quick patch. I hope that it can help
mitigate the problem.

From 379f0641e4bd7b287f398e1798530b1b09c5ad0f Mon Sep 17 00:00:00 2001
From: Marco Scardovi <scardracs@disroot.org>
Date: Sat, 30 May 2026 16:30:50 +0200
Subject: [PATCH 1/2] cpufreq/amd-pstate: Allow EPP=0 under performance policy

Under the cpufreq "performance" policy, the amd-pstate driver currently
rejects all EPP writes with -EBUSY. However, writing the EPP value of
AMD_CPPC_EPP_PERFORMANCE (0) is semantically consistent with the
performance policy as EPP=0 corresponds to the most performance-oriented
setting. Allowing EPP=0 writes under the performance policy prevents
userspace power management utilities like power-profiles-daemon from
receiving -EBUSY and failing when switching profiles.

Only reject non-zero EPP values when the policy is set to performance.

Fixes: 2064543f5ba0 ("cpufreq/amd-pstate: Rework CPPC enabling")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=221505
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Marco Scardovi <scardracs@disroot.org>
---
 drivers/cpufreq/amd-pstate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 8d55e2be825b..30b4953a93b3 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1423,7 +1423,8 @@ ssize_t store_energy_performance_preference(struct
cpufreq_policy *policy,
                        epp = cpudata->epp_default_dc;
        }

-       if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) {
+       if (epp != AMD_CPPC_EPP_PERFORMANCE &&
+           cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) {
                pr_debug("EPP cannot be set under performance policy\n");
                return -EBUSY;
        }
-- 
2.54.0

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