Re: [PATCH v5 3/3] gpio: mmio: track the direction of chips without direction registers
flat view
From: Bough Chen <hidden>
Date: 2026-09-09 06:40:08
Also in:
imx, linux-gpio, lkml
On Thu, Sep 03, 2026 at 09:59:40AM +0200, Mehmet Fide wrote:
From: Mehmet Fide <redacted> A generic chip with GPIO_GENERIC_PINCTRL_BACKEND and no direction registers sets the direction through pinctrl but has no get_direction callback, so every gpiod_get_direction() call trips the WARN in gpiolib and the direction gpiolib reports is whatever it assumed. On a Vybrid Colibri module that is 21 backtraces per boot. Keep the direction of such a chip in the existing shadow: the direction setters update sdir under the chip lock, and get_direction() is the shadow-reading path already used for unreadable direction registers. That keeps the callback usable in atomic context, which it has to be: gpiochip_lock_as_irq() calls it for !can_sleep chips from gpiochip_irq_domain_activate(), under the irq descriptor lock. The pad's actual state is read once, in process context, when a line is requested: gpiolib calls request() right before get_direction() for a new line, so the shadow is seeded there from PIN_CONFIG_OUTPUT_ENABLE through the chip's get_config(), which is gpiochip_generic_get_config() for the pinctrl backend, and the line reports what the pin controller says. Lines pinctrl cannot answer for keep the input default, which is what gpiolib assumed before.
dir_unreadable is now set from a second source (PINCTRL_BACKEND with no direction register, in addition to GPIO_GENERIC_UNREADABLE_REG_DIR); worth a line in the commit message. Reviewed-by: Haibo Chen <haibo.chen@nxp.com> Regards Haibo Chen
quoted hunk ↗ jump to hunk
Suggested-by: Bartosz Golaszewski <brgl@kernel.org> Signed-off-by: Mehmet Fide <redacted> --- drivers/gpio/gpio-mmio.c | 60 +++++++++++++++++++++++++++++++++++++--- 1 file changed, 56 insertions(+), 4 deletions(-)diff --git a/drivers/gpio/gpio-mmio.c b/drivers/gpio/gpio-mmio.c index 7e4b3e8d609f..0709ffaab4de 100644 --- a/drivers/gpio/gpio-mmio.c +++ b/drivers/gpio/gpio-mmio.c@@ -49,6 +49,7 @@ o ` ~~~~\___/~~~~ ` controller in FPGA is ,.` #include <linux/log2.h> #include <linux/module.h> #include <linux/pinctrl/consumer.h> +#include <linux/pinctrl/pinconf-generic.h> #include <linux/platform_device.h> #include <linux/property.h> #include <linux/spinlock.h>@@ -372,7 +373,17 @@ static int gpio_mmio_dir_in_err(struct gpio_chip *gc, unsigned int gpio) static int gpio_mmio_simple_dir_in(struct gpio_chip *gc, unsigned int gpio) { - return gpio_mmio_dir_return(gc, gpio, false); + struct gpio_generic_chip *chip = to_gpio_generic_chip(gc); + int ret; + + ret = gpio_mmio_dir_return(gc, gpio, false); + if (ret) + return ret; + + guard(raw_spinlock_irqsave)(&chip->lock); + chip->sdir &= ~gpio_mmio_line2mask(gc, gpio); + + return 0; } static int gpio_mmio_dir_out_err(struct gpio_chip *gc, unsigned int gpio,@@ -384,9 +395,19 @@ static int gpio_mmio_dir_out_err(struct gpio_chip *gc, unsigned int gpio, static int gpio_mmio_simple_dir_out(struct gpio_chip *gc, unsigned int gpio, int val) { + struct gpio_generic_chip *chip = to_gpio_generic_chip(gc); + int ret; + gc->set(gc, gpio, val); - return gpio_mmio_dir_return(gc, gpio, true); + ret = gpio_mmio_dir_return(gc, gpio, true); + if (ret) + return ret; + + guard(raw_spinlock_irqsave)(&chip->lock); + chip->sdir |= gpio_mmio_line2mask(gc, gpio); + + return 0; } static int gpio_mmio_dir_in(struct gpio_chip *gc, unsigned int gpio)@@ -601,20 +622,51 @@ static int gpio_mmio_setup_direction(struct gpio_generic_chip *chip, gc->direction_input = gpio_mmio_dir_in_err; else gc->direction_input = gpio_mmio_simple_dir_in; + + if (cfg->flags & GPIO_GENERIC_PINCTRL_BACKEND) { + chip->dir_unreadable = true; + gc->get_direction = gpio_mmio_get_dir; + gc->get_config = gpiochip_generic_get_config; + } } return 0; } +static void gpio_mmio_seed_dir_from_pinctrl(struct gpio_chip *gc, + unsigned int gpio) +{ + struct gpio_generic_chip *chip = to_gpio_generic_chip(gc); + unsigned long config; + + if (!gc->get_config || chip->reg_dir_out || chip->reg_dir_in) + return; + + config = pinconf_to_config_packed(PIN_CONFIG_OUTPUT_ENABLE, 0); + if (gc->get_config(gc, gpio, &config)) + return; + + guard(raw_spinlock_irqsave)(&chip->lock); + if (config) + chip->sdir |= gpio_mmio_line2mask(gc, gpio); + else + chip->sdir &= ~gpio_mmio_line2mask(gc, gpio); +} + static int gpio_mmio_request(struct gpio_chip *gc, unsigned int gpio_pin) { struct gpio_generic_chip *chip = to_gpio_generic_chip(gc); + int ret; if (gpio_pin >= gc->ngpio) return -EINVAL; - if (chip->pinctrl) - return gpiochip_generic_request(gc, gpio_pin); + if (chip->pinctrl) { + ret = gpiochip_generic_request(gc, gpio_pin); + if (ret) + return ret; + gpio_mmio_seed_dir_from_pinctrl(gc, gpio_pin); + } return 0; }-- 2.54.0