gpiolib: allow simultaneous setting of multiple GPIO outputs
Introduce new functions gpiod_set_array & gpiod_set_raw_array to the consumer
interface which allow setting multiple outputs with just one function call.
Also add an optional set_multiple function to the driver interface. Without an
implementation of that function in the chip driver outputs are set
sequentially.
Implementing the set_multiple function in a chip driver allows for:
- Improved performance for certain use cases. The original motivation for this
was the task of configuring an FPGA. In that specific case, where 9 GPIO
lines have to be set many times, configuration time goes down from 48 s to
20 s when using the new function.
- Simultaneous glitch-free setting of multiple pins on any kind of parallel
bus attached to GPIOs provided they all reside on the same chip and bank.
Limitations:
Performance is only improved for normal high-low outputs. Open drain and
open source outputs are always set separately from each other. Those kinds
of outputs could probably be accelerated in a similar way if we could
forgo the error checking when setting GPIO directions.
Change log:
v6: - rebase on current linux-gpio devel branch
v5: - check can_sleep property per chip
- remove superfluous checks
- supplement documentation
v4: - add gpiod_set_array function for setting logical values
- change interface of the set_multiple driver function to use
unsigned long as type for the bit fields
- use generic bitops (which also use unsigned long for bit fields)
- do not use ARCH_NR_GPIOS any more
v3: - add documentation
- change commit message
v2: - use descriptor interface
- allow arbitrary groups of GPIOs spanning multiple chips
Signed-off-by: Rojhalat Ibrahim <imr@rtschenk.de>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index ff200a7..c497c62 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -32,6 +32,7 @@
* @get: returns value for signal "offset"; for output signals this
* returns either the value actually sensed, or zero
* @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
* @to_irq: optional hook supporting non-static gpio_to_irq() mappings;
@@ -89,6 +90,9 @@
unsigned offset);
void (*set)(struct gpio_chip *chip,
unsigned offset, int value);
+ void (*set_multiple)(struct gpio_chip *chip,
+ unsigned long *mask,
+ unsigned long *bits);
int (*set_debounce)(struct gpio_chip *chip,
unsigned offset,
unsigned debounce);