Hi, On 05/27/2014 10:09 AM, Maxime Ripard wrote: > On Mon, May 26, 2014 at 09:47:58AM +0200, Hans de Goede wrote: >> With level triggered interrupt mask / unmask will get called for each >> interrupt, doing the somewhat expensive mux setting on each unmask thus is >> not a good idea. Instead move it to the set_type callback, which is typically >> done only once for each irq. > > *This* is the bad idea. Nothing prevents you from calling > gpio_get_value whenever you just got your interrupt, that will change > the muxing, and never change it back, effectively breaking the > interrupts. Hmm, interesting point, but your assuming 2 things which are both not true: 1) That calling gpiod_get_value changes the muxing, which is not true, all gpiod_get_value variants end up in drivers/gpio/gpiolib.c _gpiod_get_raw_value() which does no such thing 2) That unmask will always get called after the gpio_get_value to restore the mux setting for us, which is not guaranteed at all. Before this patch set pinctrl-sunxi.c was using handle_simple_irq which does not mask / unmask at all. And even with an irq-handler which masks / unmasks, what if the irq wakes up a thread and that thread then does the gpio_get_value ? Note this is *exactly* what e.g. the mmc gpio card-detect code does, it uses a thread to read the gpio for debouncing. Luckily 2. is not a problem, since 1. means that the mux won't get changed at all so we don't need to change it back. Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
