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gpio: support native single-ended hardware drivers

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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>
This commit is contained in:
Linus Walleij 2016-03-22 10:51:16 +01:00
parent 6e66a6599a
commit c663e5f567
2 changed files with 61 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

25
include/linux/gpio/driver.h
View file

@ -19,6 +19,18 @@ 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
@ -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);