pinctrl: mediatek: use spin lock in mtk_rmw

Commit 42a46434 ("pinctrl: add lock in mtk_rmw function.") uses
mutex lock in mtk_rmw.  However the function is possible called from
atomic context.

For example call trace:
  mutex_lock+0x28/0x64
  mtk_rmw+0x38/0x80
  [snip]
  max98357a_daiops_trigger+0x8c/0x9c
  soc_pcm_trigger+0x5c/0x10c

The max98357a_daiops_trigger() could run in either atomic or non-atomic
context.  As a result, dmesg shows some similar messages: "BUG: sleeping
function called from invalid context at kernel/locking/mutex.c:254".

Uses spin lock in mtk_rmw instead.

Fixes: 42a46434 ("pinctrl: add lock in mtk_rmw function.")
Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20210419093449.3125704-1-tzungbi@google.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/mediatek/pinctrl-moore.c

@@ -619,7 +619,7 @@ int mtk_moore_pinctrl_probe(struct platform_device *pdev,
 
 	hw->nbase = hw->soc->nbase_names;
 
-	mutex_init(&hw->lock);
+	spin_lock_init(&hw->lock);
 
 	/* Copy from internal struct mtk_pin_desc to register to the core */
 	pins = devm_kmalloc_array(&pdev->dev, hw->soc->npins, sizeof(*pins),

drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.c

@@ -57,15 +57,16 @@ static u32 mtk_r32(struct mtk_pinctrl *pctl, u8 i, u32 reg)
 void mtk_rmw(struct mtk_pinctrl *pctl, u8 i, u32 reg, u32 mask, u32 set)
 {
 	u32 val;
+	unsigned long flags;
 
-	mutex_lock(&pctl->lock);
+	spin_lock_irqsave(&pctl->lock, flags);
 
 	val = mtk_r32(pctl, i, reg);
 	val &= ~mask;
 	val |= set;
 	mtk_w32(pctl, i, reg, val);
 
-	mutex_unlock(&pctl->lock);
+	spin_unlock_irqrestore(&pctl->lock, flags);
 }
 
 static int mtk_hw_pin_field_lookup(struct mtk_pinctrl *hw,

drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.h

@@ -253,7 +253,7 @@ struct mtk_pinctrl {
 	struct mtk_pinctrl_group	*groups;
 	const char          **grp_names;
 	/* lock pin's register resource to avoid multiple threads issue*/
-	struct mutex lock;
+	spinlock_t lock;
 };
 
 void mtk_rmw(struct mtk_pinctrl *pctl, u8 i, u32 reg, u32 mask, u32 set);

drivers/pinctrl/mediatek/pinctrl-paris.c

@@ -970,7 +970,7 @@ int mtk_paris_pinctrl_probe(struct platform_device *pdev,
 
 	hw->nbase = hw->soc->nbase_names;
 
-	mutex_init(&hw->lock);
+	spin_lock_init(&hw->lock);
 
 	err = mtk_pctrl_build_state(pdev);
 	if (err) {