Re: [PATCH] gpio: mmio: do not calculate bgpio_bits via "ngpios"
From: Linus Walleij
Date: Wed Jun 26 2024 - 08:07:00 EST
Hi Shiji,
thanks for your patch!
On Tue, Jun 25, 2024 at 3:22 AM Shiji Yang <yangshiji66@xxxxxxxxxxx> wrote:
> bgpio_bits must be aligned with the data bus width. For example, on a
> 32 bit big endian system and we only have 16 GPIOs. If we only assume
> bgpio_bits=16 we can never control the GPIO because the base address
> is the lowest address.
>
> low address high address
> -------------------------------------------------
> | byte3 | byte2 | byte1 | byte0 |
> -------------------------------------------------
> | NaN | NaN | gpio8-15 | gpio0-7 |
> -------------------------------------------------
>
> Fixes: 55b2395e4e92 ("gpio: mmio: handle "ngpios" properly in bgpio_init()")
> Fixes: https://github.com/openwrt/openwrt/issues/15739
> Reported-by: Mark Mentovai <mark@xxxxxxxxxxxx>
> Signed-off-by: Shiji Yang <yangshiji66@xxxxxxxxxxx>
> Suggested-By: Mark Mentovai <mark@xxxxxxxxxxxx>
> Reviewed-by: Jonas Gorski <jonas.gorski@xxxxxxxxx>
> Tested-by: Lóránd Horváth <lorand.horvath82@xxxxxxxxx>
Commit 55b2395e4e92 also contains this:
@@ -614,10 +616,15 @@ int bgpio_init(struct gpio_chip *gc, struct device *dev,
gc->parent = dev;
gc->label = dev_name(dev);
gc->base = -1;
- gc->ngpio = gc->bgpio_bits;
gc->request = bgpio_request;
After this patch gc->ngpio will be unset for any GPIO chip that
provides a ngpios property, so restore the above line too.
But maybe a better fix is:
+ #include <linux/types.h>
(...)
+ else
+ gc->bgpio_bits = round_up(gc->ngpio, sizeof(phys_addr_t) * 8);
?
Yours,
Linus Walleij