From: Bartosz Golaszewski bgolaszewski@baylibre.com

When emulating open-drain/open-source by not actively driving the output lines - we're simply changing their mode to input. This is wrong as it will then make it impossible to change the value of such line - it's now considered to actually be in input mode. If we want to still use the direction_input() callback for simplicity then we need to set FLAG_IS_OUT manually in gpiod_direction_output() and not clear it in gpio_set_open_drain_value_commit() and gpio_set_open_source_value_commit().

Fixes: c663e5f56737 ("gpio: support native single-ended hardware drivers") Cc: stable@vger.kernel.org Reported-by: Kent Gibson warthog618@gmail.com Signed-off-by: Bartosz Golaszewski bgolaszewski@baylibre.com [Bartosz: backported to v5.3, v4.19] Signed-off-by: Bartosz Golaszewski bgolaszewski@baylibre.com --- drivers/gpio/gpiolib.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index e4203c1eb869..74a77001b1bd 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -2775,8 +2775,10 @@ int gpiod_direction_output(struct gpio_desc *desc, int value) if (!ret) goto set_output_value; /* Emulate open drain by not actively driving the line high */ - if (value) - return gpiod_direction_input(desc); + if (value) { + ret = gpiod_direction_input(desc); + goto set_output_flag; + } } else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags)) { ret = gpio_set_config(gc, gpio_chip_hwgpio(desc), @@ -2784,8 +2786,10 @@ int gpiod_direction_output(struct gpio_desc *desc, int value) if (!ret) goto set_output_value; /* Emulate open source by not actively driving the line low */ - if (!value) - return gpiod_direction_input(desc); + if (!value) { + ret = gpiod_direction_input(desc); + goto set_output_flag; + } } else { gpio_set_config(gc, gpio_chip_hwgpio(desc), PIN_CONFIG_DRIVE_PUSH_PULL); @@ -2793,6 +2797,17 @@ int gpiod_direction_output(struct gpio_desc *desc, int value)

set_output_value: return gpiod_direction_output_raw_commit(desc, value); + +set_output_flag: + /* + * When emulating open-source or open-drain functionalities by not + * actively driving the line (setting mode to input) we still need to + * set the IS_OUT flag or otherwise we won't be able to set the line + * value anymore. + */ + if (ret == 0) + set_bit(FLAG_IS_OUT, &desc->flags); + return ret; } EXPORT_SYMBOL_GPL(gpiod_direction_output);

@@ -3153,8 +3168,6 @@ static void gpio_set_open_drain_value_commit(struct gpio_desc *desc, bool value)

if (value) { err = chip->direction_input(chip, offset); - if (!err) - clear_bit(FLAG_IS_OUT, &desc->flags); } else { err = chip->direction_output(chip, offset, 0); if (!err) @@ -3184,8 +3197,6 @@ static void gpio_set_open_source_value_commit(struct gpio_desc *desc, bool value set_bit(FLAG_IS_OUT, &desc->flags); } else { err = chip->direction_input(chip, offset); - if (!err) - clear_bit(FLAG_IS_OUT, &desc->flags); } trace_gpio_direction(desc_to_gpio(desc), !value, err); if (err < 0)