[PATCH v4.14] gpiolib: don't clear FLAG_IS_OUT when emulating open-drain/open-source

[Bartosz Golaszewski <brgl@bgdev.pl>]

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)
-- 
2.23.0