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 v4.14] 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 f1809a54fcee..c7f5f0be2d74 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -2329,8 +2329,10 @@ static int _gpiod_direction_output_raw(struct gpio_desc *desc, int value) if (!ret) goto set_output_value; /* Emulate open drain by not actively driving the line high */ - if (val) - return gpiod_direction_input(desc); + if (val) { + ret = gpiod_direction_input(desc); + goto set_output_flag; + } } else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags)) { ret = gpio_set_drive_single_ended(gc, gpio_chip_hwgpio(desc), @@ -2338,8 +2340,10 @@ static int _gpiod_direction_output_raw(struct gpio_desc *desc, int value) if (!ret) goto set_output_value; /* Emulate open source by not actively driving the line low */ - if (!val) - return gpiod_direction_input(desc); + if (!val) { + ret = gpiod_direction_input(desc); + goto set_output_flag; + } } else { gpio_set_drive_single_ended(gc, gpio_chip_hwgpio(desc), PIN_CONFIG_DRIVE_PUSH_PULL); @@ -2359,6 +2363,17 @@ static int _gpiod_direction_output_raw(struct gpio_desc *desc, int value) trace_gpio_value(desc_to_gpio(desc), 0, val); trace_gpio_direction(desc_to_gpio(desc), 0, ret); return ret; + +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; }

/** @@ -2540,8 +2555,6 @@ static void _gpio_set_open_drain_value(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) @@ -2571,8 +2584,6 @@ static void _gpio_set_open_source_value(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)