From: Andy Shevchenko andriy.shevchenko@linux.intel.com
[ Upstream commit 064c73afe7385de99e5b2785b88c83dc5d84403b ]
Since the commit aa58a21ae378 ("gpio: pca953x: disable regmap locking") the locking of regmap is disabled and that immediately introduces a synchronization issue. It's easy to see when we try to monitor more than one interrupt from the same chip.
It seems that the problem exists from the day one and even commit 6e20fb18054c ("drivers/gpio/pca953x.c: add a mutex to fix race condition") missed this.
Below are the traces and shell reproducers before and after proposed change. Note duplicates in the IRQ events. /proc/interrupts also shows a deviation, i.e. sum of children interrupts higher than parent's one.
When locking is disabled for regmap and no protection in IRQ handler ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ... gpioset-194 regmap_hw_write_start: i2c-INT3491:02 reg=2 count=1 irq/31-i2c-INT3-139 regmap_hw_read_start: i2c-INT3491:02 reg=4c count=2 gpioset-194 regmap_hw_write_done: i2c-INT3491:02 reg=2 count=1 gpioset-194 regmap_reg_read_cache: i2c-INT3491:02 reg=6 val=f5 gpioset-194 regmap_reg_write: i2c-INT3491:02 reg=6 val=f5 gpioset-194 regmap_hw_write_start: i2c-INT3491:02 reg=6 count=1 irq/31-i2c-INT3-139 regmap_hw_read_done: i2c-INT3491:02 reg=4c count=2 ...
% gpiomon gpiochip3 0 & % gpioset gpiochip3 1=0 % gpioset gpiochip3 1=1 event: RISING EDGE offset: 0 timestamp: [ 302.782583765] % gpiomon gpiochip3 2 & % gpioset gpiochip3 1=0 event: RISING EDGE offset: 2 timestamp: [ 312.033148829] event: FALLING EDGE offset: 0 timestamp: [ 312.022757525] % gpioset gpiochip3 1=1 event: RISING EDGE offset: 2 timestamp: [ 316.201148473] event: RISING EDGE offset: 0 timestamp: [ 316.191759599]
When locking is disabled for regmap and protection in IRQ handler ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ... gpioset-202 regmap_hw_write_start: i2c-INT3491:02 reg=2 count=1 gpioset-202 regmap_hw_write_done: i2c-INT3491:02 reg=2 count=1 gpioset-202 regmap_reg_read_cache: i2c-INT3491:02 reg=6 val=fd gpioset-202 regmap_reg_write: i2c-INT3491:02 reg=6 val=fd gpioset-202 regmap_hw_write_start: i2c-INT3491:02 reg=6 count=1 gpioset-202 regmap_hw_write_done: i2c-INT3491:02 reg=6 count=1 irq/31-i2c-INT3-139 regmap_hw_read_start: i2c-INT3491:02 reg=4c count=2 irq/31-i2c-INT3-139 regmap_hw_read_done: i2c-INT3491:02 reg=4c count=2 ...
% gpiomon gpiochip3 0 & % gpioset gpiochip3 1=0 event: FALLING EDGE offset: 0 timestamp: [ 531.330078107] % gpioset gpiochip3 1=1 event: RISING EDGE offset: 0 timestamp: [ 532.912239128] % gpiomon gpiochip3 2 & % gpioset gpiochip3 1=0 event: FALLING EDGE offset: 0 timestamp: [ 539.633669484] % gpioset gpiochip3 1=1 event: RISING EDGE offset: 0 timestamp: [ 542.256978461]
Fixes: 6e20fb18054c ("drivers/gpio/pca953x.c: add a mutex to fix race condition") Depends-on: 35d13d94893f ("gpio: pca953x: convert to use bitmap API") Depends-on: 49427232764d ("gpio: pca953x: Perform basic regmap conversion") Cc: Marek Vasut marek.vasut@gmail.com Cc: Roland Stigge stigge@antcom.de Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Signed-off-by: Bartosz Golaszewski bgolaszewski@baylibre.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpio/gpio-pca953x.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c index 01011a780688a..d8ba6c5195be7 100644 --- a/drivers/gpio/gpio-pca953x.c +++ b/drivers/gpio/gpio-pca953x.c @@ -724,14 +724,16 @@ static irqreturn_t pca953x_irq_handler(int irq, void *devid) struct gpio_chip *gc = &chip->gpio_chip; DECLARE_BITMAP(pending, MAX_LINE); int level; + bool ret;
- if (!pca953x_irq_pending(chip, pending)) - return IRQ_NONE; + mutex_lock(&chip->i2c_lock); + ret = pca953x_irq_pending(chip, pending); + mutex_unlock(&chip->i2c_lock);
for_each_set_bit(level, pending, gc->ngpio) handle_nested_irq(irq_find_mapping(gc->irq.domain, level));
- return IRQ_HANDLED; + return IRQ_RETVAL(ret); }
static int pca953x_irq_setup(struct pca953x_chip *chip, int irq_base)