diff mbox series

gpio: mmio: do not calculate bgpio_bits via "ngpios"

Message ID TYCP286MB089577B47D70F0AB25ABA6F5BCD52@TYCP286MB0895.JPNP286.PROD.OUTLOOK.COM
State New
Headers show
Series gpio: mmio: do not calculate bgpio_bits via "ngpios" | expand

Commit Message

Shiji Yang June 25, 2024, 1:19 a.m. UTC 
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@mentovai.com>
Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Suggested-By: Mark Mentovai <mark@mentovai.com>
Reviewed-by: Jonas Gorski <jonas.gorski@gmail.com>
Tested-by: Lóránd Horváth <lorand.horvath82@gmail.com>
---
 drivers/gpio/gpio-mmio.c | 2 --
 1 file changed, 2 deletions(-)

Comments

Linus Walleij July 3, 2024, 12:38 p.m. UTC | #1 
On Tue, Jun 25, 2024 at 3:22 AM Shiji Yang <yangshiji66@outlook.com> 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@mentovai.com>
> Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
> Suggested-By: Mark Mentovai <mark@mentovai.com>
> Reviewed-by: Jonas Gorski <jonas.gorski@gmail.com>
> Tested-by: Lóránd Horváth <lorand.horvath82@gmail.com>

I'm convinced this is the right thing to do. (By Jonas Gorski.)
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Bart, can you apply it for fixes?
(Or for -next if you wanna be really careful.)

Yours,
Linus Walleij
Bartosz Golaszewski July 3, 2024, 1:28 p.m. UTC | #2 
From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>


On Tue, 25 Jun 2024 09:19:49 +0800, Shiji Yang 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  |
> -------------------------------------------------
> 
> [...]

Applied, thanks!

[1/1] gpio: mmio: do not calculate bgpio_bits via "ngpios"
      commit: f07798d7bb9c46d17d80103fb772fd2c75d47919

Best regards,
diff mbox series

Patch

diff --git a/drivers/gpio/gpio-mmio.c b/drivers/gpio/gpio-mmio.c
index 71e1af7c2184..d89e78f0ead3 100644
--- a/drivers/gpio/gpio-mmio.c
+++ b/drivers/gpio/gpio-mmio.c
@@ -619,8 +619,6 @@  int bgpio_init(struct gpio_chip *gc, struct device *dev,
 	ret = gpiochip_get_ngpios(gc, dev);
 	if (ret)
 		gc->ngpio = gc->bgpio_bits;
-	else
-		gc->bgpio_bits = roundup_pow_of_two(round_up(gc->ngpio, 8));
 
 	ret = bgpio_setup_io(gc, dat, set, clr, flags);
 	if (ret)