Patch "pinctrl-bcm2835.c: fix race condition when setting gpio dir" has been added to the 6.3-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    pinctrl-bcm2835.c: fix race condition when setting gpio dir

to the 6.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     pinctrl-bcm2835.c-fix-race-condition-when-setting-gp.patch
and it can be found in the queue-6.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9830cf948a9196ab87c663771e7453dda8724b57
Author: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Date:   Thu Apr 20 14:47:05 2023 +0200

    pinctrl-bcm2835.c: fix race condition when setting gpio dir
    
    [ Upstream commit b7badd752de05312fdb1aeb388480f706d0c087f ]
    
    In the past setting the pin direction called pinctrl_gpio_direction()
    which uses a mutex to serialize this. That was changed to set the
    direction directly in the pin controller driver, but that lost the
    serialization mechanism. Since the direction of multiple pins are in
    the same register you can have a race condition, something that was
    in fact observed with the cec-gpio driver.
    
    Add a new spinlock to serialize writing to the FSEL registers.
    
    Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
    Fixes: 1a4541b68e25 ("pinctrl-bcm2835: don't call pinctrl_gpio_direction()")
    Link: https://lore.kernel.org/r/4302b66b-ca20-0f19-d2aa-ee8661118863@xxxxxxxxx
    Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/pinctrl/bcm/pinctrl-bcm2835.c b/drivers/pinctrl/bcm/pinctrl-bcm2835.c
index 8e2551a08c372..7435173e10f43 100644
--- a/drivers/pinctrl/bcm/pinctrl-bcm2835.c
+++ b/drivers/pinctrl/bcm/pinctrl-bcm2835.c
@@ -90,6 +90,8 @@ struct bcm2835_pinctrl {
 	struct pinctrl_gpio_range gpio_range;
 
 	raw_spinlock_t irq_lock[BCM2835_NUM_BANKS];
+	/* Protect FSEL registers */
+	spinlock_t fsel_lock;
 };
 
 /* pins are just named GPIO0..GPIO53 */
@@ -284,14 +286,19 @@ static inline void bcm2835_pinctrl_fsel_set(
 		struct bcm2835_pinctrl *pc, unsigned pin,
 		enum bcm2835_fsel fsel)
 {
-	u32 val = bcm2835_gpio_rd(pc, FSEL_REG(pin));
-	enum bcm2835_fsel cur = (val >> FSEL_SHIFT(pin)) & BCM2835_FSEL_MASK;
+	u32 val;
+	enum bcm2835_fsel cur;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pc->fsel_lock, flags);
+	val = bcm2835_gpio_rd(pc, FSEL_REG(pin));
+	cur = (val >> FSEL_SHIFT(pin)) & BCM2835_FSEL_MASK;
 
 	dev_dbg(pc->dev, "read %08x (%u => %s)\n", val, pin,
-			bcm2835_functions[cur]);
+		bcm2835_functions[cur]);
 
 	if (cur == fsel)
-		return;
+		goto unlock;
 
 	if (cur != BCM2835_FSEL_GPIO_IN && fsel != BCM2835_FSEL_GPIO_IN) {
 		/* always transition through GPIO_IN */
@@ -309,6 +316,9 @@ static inline void bcm2835_pinctrl_fsel_set(
 	dev_dbg(pc->dev, "write %08x (%u <= %s)\n", val, pin,
 			bcm2835_functions[fsel]);
 	bcm2835_gpio_wr(pc, FSEL_REG(pin), val);
+
+unlock:
+	spin_unlock_irqrestore(&pc->fsel_lock, flags);
 }
 
 static int bcm2835_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
@@ -1248,6 +1258,7 @@ static int bcm2835_pinctrl_probe(struct platform_device *pdev)
 	pc->gpio_chip = *pdata->gpio_chip;
 	pc->gpio_chip.parent = dev;
 
+	spin_lock_init(&pc->fsel_lock);
 	for (i = 0; i < BCM2835_NUM_BANKS; i++) {
 		unsigned long events;
 		unsigned offset;