firmware/psci: Print a warning if PSCI doesn't accept PC mode

The function psci_pd_try_set_osi_mode() will print an error if enabling
OSI mode fails. To ease debugging PSCI issues print corresponding
message if switching to PC mode fails too.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20220926110249.666813-1-dmitry.baryshkov@linaro.org'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/cpuidle/cpuidle-psci-domain.c

@@ -124,10 +124,8 @@ static bool psci_pd_try_set_osi_mode(void)
 		return false;
 
 	ret = psci_set_osi_mode(true);
-	if (ret) {
-		pr_warn("failed to enable OSI mode: %d\n", ret);
+	if (ret)
 		return false;
-	}
 
 	return true;
 }

drivers/firmware/psci/psci.c

@@ -163,6 +163,8 @@ int psci_set_osi_mode(bool enable)
 			PSCI_1_0_SUSPEND_MODE_PC;
 
 	err = invoke_psci_fn(PSCI_1_0_FN_SET_SUSPEND_MODE, suspend_mode, 0, 0);
+	if (err < 0)
+		pr_warn("failed to set %s mode: %d\n", enable ? "OSI" : "PC", err);
 	return psci_to_linux_errno(err);
 }