linux-kernel - [PATCH] gpio: mmio: do not calculate bgpio

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Message-ID:
 <TYCP286MB089577B47D70F0AB25ABA6F5BCD52@TYCP286MB0895.JPNP286.PROD.OUTLOOK.COM>
Date: Tue, 25 Jun 2024 09:19:49 +0800
From: Shiji Yang <yangshiji66@...look.com>
To: linux-gpio@...r.kernel.org
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Asmaa Mnebhi <asmaa@...dia.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	linux-kernel@...r.kernel.org,
	Shiji Yang <yangshiji66@...look.com>,
	Mark Mentovai <mark@...tovai.com>,
	Jonas Gorski <jonas.gorski@...il.com>,
	Lóránd Horváth <lorand.horvath82@...il.com>
Subject: [PATCH] gpio: mmio: do not calculate bgpio_bits via "ngpios"

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@...tovai.com>
Signed-off-by: Shiji Yang <yangshiji66@...look.com>
Suggested-By: Mark Mentovai <mark@...tovai.com>
Reviewed-by: Jonas Gorski <jonas.gorski@...il.com>
Tested-by: Lóránd Horváth <lorand.horvath82@...il.com>
---
 drivers/gpio/gpio-mmio.c | 2 --
 1 file changed, 2 deletions(-)

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)
-- 
2.45.1