[PATCH 2/4] cpufreq: amd-pstate: Propagate cppc_set_auto_sel() errors on mode change

[Mario Limonciello]

amd_pstate_change_mode_without_dvr_change() iterates over the online CPUs
and calls cppc_set_auto_sel() to enable or disable hardware autonomous
selection, but discards its return value and unconditionally returns 0.

If the firmware rejects the request, the failure is hidden: the cpufreq
core records the mode transition as successful while the hardware stays in
its previous autonomous-selection state.  The software mode and the actual
hardware behaviour then disagree, breaking the expected frequency scaling.

Check the return value of cppc_set_auto_sel() and propagate the first
error to the caller so the sysfs write reports the failure.

Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Closes: https://sashiko.dev/#/bug/linux-d114a94a-655b-43a6-91b1-9484889726c9
Fixes: 3ca7bc818d8c ("cpufreq: amd-pstate: Add guided mode control support via sysfs")
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
 drivers/cpufreq/amd-pstate.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index f633a8e349255..7a2174b5911e4 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1818,6 +1818,7 @@ static int amd_pstate_unregister_driver(int dummy)
 static int amd_pstate_change_mode_without_dvr_change(int mode)
 {
 	int cpu = 0;
+	int ret;
 
 	cppc_state = mode;
 
@@ -1825,7 +1826,9 @@ static int amd_pstate_change_mode_without_dvr_change(int mode)
 		return 0;
 
 	for_each_online_cpu(cpu) {
-		cppc_set_auto_sel(cpu, (cppc_state == AMD_PSTATE_PASSIVE) ? 0 : 1);
+		ret = cppc_set_auto_sel(cpu, (cppc_state == AMD_PSTATE_PASSIVE) ? 0 : 1);
+		if (ret)
+			return ret;
 	}
 
 	return 0;
-- 
2.43.0