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Subject[PATCH 5.11 721/775] gpio: pcf857x: Fix missing first interrupt
Date
From: Maxim Kiselev <bigunclemax@gmail.com>

commit a8002a35935aaefcd6a42ad3289f62bab947f2ca upstream.

If no n_latch value will be provided at driver probe then all pins will
be used as an input:

gpio->out = ~n_latch;

In that case initial state for all pins is "one":

gpio->status = gpio->out;

So if pcf857x IRQ happens with change pin value from "zero" to "one"
then we miss it, because of "one" from IRQ and "one" from initial state
leaves corresponding pin unchanged:
change = (gpio->status ^ status) & gpio->irq_enabled;

The right solution will be to read actual state at driver probe.

Cc: stable@vger.kernel.org
Fixes: 6e20a0a429bd ("gpio: pcf857x: enable gpio_to_irq() support")
Signed-off-by: Maxim Kiselev <bigunclemax@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpio/gpio-pcf857x.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpio/gpio-pcf857x.c
+++ b/drivers/gpio/gpio-pcf857x.c
@@ -332,7 +332,7 @@ static int pcf857x_probe(struct i2c_clie
* reset state. Otherwise it flags pins to be driven low.
*/
gpio->out = ~n_latch;
- gpio->status = gpio->out;
+ gpio->status = gpio->read(gpio->client);

/* Enable irqchip if we have an interrupt */
if (client->irq) {

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