From 591cdccebdd4d02eb46d400dea911136400cc567 Mon Sep 17 00:00:00 2001
From: Lorenzo Bianconi <lorenzo@kernel.org>
Date: Thu, 30 Dec 2021 21:47:05 +0100
Subject: [PATCH] mt76: mt7921: fix a leftover race in runtime-pm
Git-commit: 591cdccebdd4d02eb46d400dea911136400cc567
Patch-mainline: v5.18-rc1
References: git-fixes

Fix a possible race in mt7921_pm_power_save_work() if rx/tx napi
schedules ps_work and we are currently accessing device register
on a different cpu.

Fixes: 1d8efc741df8 ("mt76: mt7921: introduce Runtime PM support")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/net/wireless/mediatek/mt76/mt7921/mac.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
@@ -1550,6 +1550,14 @@ void mt7921_pm_power_save_work(struct wo
 	    test_bit(MT76_HW_SCHED_SCANNING, &mphy->state))
 		goto out;
 
+	if (mutex_is_locked(&dev->mt76.mutex))
+		/* if mt76 mutex is held we should not put the device
+		 * to sleep since we are currently accessing device
+		 * register map. We need to wait for the next power_save
+		 * trigger.
+		 */
+		goto out;
+
 	if (time_is_after_jiffies(dev->pm.last_activity + delta)) {
 		delta = dev->pm.last_activity + delta - jiffies;
 		goto out;