@@ -1509,8 +1509,8 @@ EXPORT_SYMBOL_GPL(gpiod_direction_input);
static int _gpiod_direction_output_raw(struct gpio_desc *desc, int value)
{
- struct gpio_chip *chip;
- int status = -EINVAL;
+ struct gpio_chip *gc = desc->gdev->chip;
+ int ret;
/* GPIOs used for IRQs shall not be set as output */
if (test_bit(FLAG_USED_AS_IRQ, &desc->flags)) {
@@ -1520,28 +1520,50 @@ static int _gpiod_direction_output_raw(struct gpio_desc *desc, int value)
return -EIO;
}
- /* Open drain pin should not be driven to 1 */
- if (value && test_bit(FLAG_OPEN_DRAIN, &desc->flags))
- return gpiod_direction_input(desc);
-
- /* Open source pin should not be driven to 0 */
- if (!value && test_bit(FLAG_OPEN_SOURCE, &desc->flags))
- return gpiod_direction_input(desc);
+ if (test_bit(FLAG_OPEN_DRAIN, &desc->flags)) {
+ /* First see if we can enable open drain in hardware */
+ if (gc->set_single_ended) {
+ ret = gc->set_single_ended(gc, gpio_chip_hwgpio(desc),
+ LINE_MODE_OPEN_DRAIN);
+ if (!ret)
+ goto set_output_value;
+ }
+ /* Emulate open drain by not actively driving the line high */
+ if (value)
+ return gpiod_direction_input(desc);
+ }
+ else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags)) {
+ if (gc->set_single_ended) {
+ ret = gc->set_single_ended(gc, gpio_chip_hwgpio(desc),
+ LINE_MODE_OPEN_SOURCE);
+ if (!ret)
+ goto set_output_value;
+ }
+ /* Emulate open source by not actively driving the line low */
+ if (!value)
+ return gpiod_direction_input(desc);
+ } else {
+ /* Make sure to disable open drain/source hardware, if any */
+ if (gc->set_single_ended)
+ gc->set_single_ended(gc,
+ gpio_chip_hwgpio(desc),
+ LINE_MODE_PUSH_PULL);
+ }
- chip = desc->gdev->chip;
- if (!chip->set || !chip->direction_output) {
+set_output_value:
+ if (!gc->set || !gc->direction_output) {
gpiod_warn(desc,
"%s: missing set() or direction_output() operations\n",
__func__);
return -EIO;
}
- status = chip->direction_output(chip, gpio_chip_hwgpio(desc), value);
- if (status == 0)
+ ret = gc->direction_output(gc, gpio_chip_hwgpio(desc), value);
+ if (!ret)
set_bit(FLAG_IS_OUT, &desc->flags);
trace_gpio_value(desc_to_gpio(desc), 0, value);
- trace_gpio_direction(desc_to_gpio(desc), 0, status);
- return status;
+ trace_gpio_direction(desc_to_gpio(desc), 0, ret);
+ return ret;
}
/**
@@ -20,6 +20,18 @@ struct gpio_device;
#ifdef CONFIG_GPIOLIB
/**
+ * enum single_ended_mode - mode for single ended operation
+ * @LINE_MODE_PUSH_PULL: normal mode for a GPIO line, drive actively high/low
+ * @LINE_MODE_OPEN_DRAIN: set line to be open drain
+ * @LINE_MODE_OPEN_SOURCE: set line to be open source
+ */
+enum single_ended_mode {
+ LINE_MODE_PUSH_PULL,
+ LINE_MODE_OPEN_DRAIN,
+ LINE_MODE_OPEN_SOURCE,
+};
+
+/**
* struct gpio_chip - abstract a GPIO controller
* @label: a functional name for the GPIO device, such as a part
* number or the name of the SoC IP-block implementing it.
@@ -38,7 +50,15 @@ struct gpio_device;
* @set: assigns output value for signal "offset"
* @set_multiple: assigns output values for multiple signals defined by "mask"
* @set_debounce: optional hook for setting debounce time for specified gpio in
- * interrupt triggered gpio chips
+ * interrupt triggered gpio chips
+ * @set_single_ended: optional hook for setting a line as open drain, open
+ * source, or non-single ended (restore from open drain/source to normal
+ * push-pull mode) this should be implemented if the hardware supports
+ * open drain or open source settings. The GPIOlib will otherwise try
+ * to emulate open drain/source by not actively driving lines high/low
+ * if a consumer request this. The driver may return -ENOTSUPP if e.g.
+ * it supports just open drain but not open source and is called
+ * with LINE_MODE_OPEN_SOURCE as mode argument.
* @to_irq: optional hook supporting non-static gpio_to_irq() mappings;
* implementation may not sleep
* @dbg_show: optional routine to show contents in debugfs; default code
@@ -130,6 +150,9 @@ struct gpio_chip {
int (*set_debounce)(struct gpio_chip *chip,
unsigned offset,
unsigned debounce);
+ int (*set_single_ended)(struct gpio_chip *chip,
+ unsigned offset,
+ enum single_ended_mode mode);
int (*to_irq)(struct gpio_chip *chip,
unsigned offset);
Some GPIO controllers has a special hardware bit we can flip to support open drain / source. This means that on these hardwares we do not need to emulate OD/OS by setting the line to input instead of actively driving it high/low. Add an optional vtable callback to the driver set_single_ended() so that driver can implement this in hardware if they have it. We may need a pinctrl_gpio_set_config() call at some point to propagate this down to a backing pin control device on systems with split GPIO/pin control. Reported-by: Michael Hennerich <michael.hennerich@analog.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> --- Michael, please have a look at this and consider testing it with your hardware and adding a .set_single_ended() callback in your driver to see if it does what you want. I'm ready to merge this if at least one driver make use of it. --- drivers/gpio/gpiolib.c | 52 ++++++++++++++++++++++++++++++++------------- include/linux/gpio/driver.h | 25 +++++++++++++++++++++- 2 files changed, 61 insertions(+), 16 deletions(-)