Commit bf9346f5 authored by Janusz Krzysztofik's avatar Janusz Krzysztofik Committed by Linus Walleij
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gpiolib: Identify arrays matching GPIO hardware 



Certain GPIO array lookup results may map directly to GPIO pins of a
single GPIO chip in hardware order.  If that condition is recognized
and handled efficiently, significant performance gain of get/set array
functions may be possible.

While processing a request for an array of GPIO descriptors, identify
those which represent corresponding pins of a single GPIO chip.  Skip
over pins which require open source or open drain special processing.
Moreover, identify pins which require inversion.  Pass a pointer to
that information with the array to the caller so it can benefit from
enhanced performance as soon as get/set array functions can accept and
make efficient use of it.

Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: default avatarJanusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent b9762beb

Documentation/driver-api/gpio/consumer.rst

+3 −1
Original line number Diff line number Diff line
@@ -109,9 +109,11 @@ For a function using multiple GPIOs all of those can be obtained with one call:: 
					   enum gpiod_flags flags)



This function returns a struct gpio_descs which contains an array of

descriptors::

descriptors.  It also contains a pointer to a gpiolib private structure which,

if passed back to get/set array functions, may speed up I/O proocessing::



	struct gpio_descs {

		struct gpio_array *info;

		unsigned int ndescs;

		struct gpio_desc *desc[];

	}

drivers/gpio/gpiolib.c

+71 −1
Original line number Diff line number Diff line
@@ -4174,7 +4174,9 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, 
{

	struct gpio_desc *desc;

	struct gpio_descs *descs;

	int count;

	struct gpio_array *array_info = NULL;

	struct gpio_chip *chip;

	int count, bitmap_size;



	count = gpiod_count(dev, con_id);

	if (count < 0)
@@ -4190,9 +4192,77 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, 
			gpiod_put_array(descs);

			return ERR_CAST(desc);

		}



		descs->desc[descs->ndescs] = desc;



		chip = gpiod_to_chip(desc);

		/*

		 * Select a chip of first array member

		 * whose index matches its pin hardware number

		 * as a candidate for fast bitmap processing.

		 */

		if (!array_info && gpio_chip_hwgpio(desc) == descs->ndescs) {

			struct gpio_descs *array;



			bitmap_size = BITS_TO_LONGS(chip->ngpio > count ?

						    chip->ngpio : count);



			array = kzalloc(struct_size(descs, desc, count) +

					struct_size(array_info, invert_mask,

					3 * bitmap_size), GFP_KERNEL);

			if (!array) {

				gpiod_put_array(descs);

				return ERR_PTR(-ENOMEM);

			}



			memcpy(array, descs,

			       struct_size(descs, desc, descs->ndescs + 1));

			kfree(descs);



			descs = array;

			array_info = (void *)(descs->desc + count);

			array_info->get_mask = array_info->invert_mask +

						  bitmap_size;

			array_info->set_mask = array_info->get_mask +

						  bitmap_size;



			array_info->desc = descs->desc;

			array_info->size = count;

			array_info->chip = chip;

			bitmap_set(array_info->get_mask, descs->ndescs,

				   count - descs->ndescs);

			bitmap_set(array_info->set_mask, descs->ndescs,

				   count - descs->ndescs);

			descs->info = array_info;

		}

		/*

		 * Unmark members which don't qualify for fast bitmap

		 * processing (different chip, not in hardware order)

		 */

		if (array_info && (chip != array_info->chip ||

		    gpio_chip_hwgpio(desc) != descs->ndescs)) {

			__clear_bit(descs->ndescs, array_info->get_mask);

			__clear_bit(descs->ndescs, array_info->set_mask);

		} else if (array_info) {

			/* Exclude open drain or open source from fast output */

			if (gpiochip_line_is_open_drain(chip, descs->ndescs) ||

			    gpiochip_line_is_open_source(chip, descs->ndescs))

				__clear_bit(descs->ndescs,

					    array_info->set_mask);

			/* Identify 'fast' pins which require invertion */

			if (gpiod_is_active_low(desc))

				__set_bit(descs->ndescs,

					  array_info->invert_mask);

		}



		descs->ndescs++;

	}

	if (array_info)

		dev_dbg(dev,

			"GPIO array info: chip=%s, size=%d, get_mask=%lx, set_mask=%lx, invert_mask=%lx\n",

			array_info->chip->label, array_info->size,

			*array_info->get_mask, *array_info->set_mask,

			*array_info->invert_mask);

	return descs;

}

EXPORT_SYMBOL_GPL(gpiod_get_array);

drivers/gpio/gpiolib.h

+9 −0
Original line number Diff line number Diff line
@@ -183,6 +183,15 @@ static inline bool acpi_can_fallback_to_crs(struct acpi_device *adev, 
}

#endif



struct gpio_array {

	struct gpio_desc	**desc;

	unsigned int		size;

	struct gpio_chip	*chip;

	unsigned long		*get_mask;

	unsigned long		*set_mask;

	unsigned long		invert_mask[];

};



struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip, u16 hwnum);

int gpiod_get_array_value_complex(bool raw, bool can_sleep,

				  unsigned int array_size,

include/linux/gpio/consumer.h

+9 −0
Original line number Diff line number Diff line
@@ -17,11 +17,20 @@ struct device; 
 */

struct gpio_desc;



/**

 * Opaque descriptor for a structure of GPIO array attributes.  This structure

 * is attached to struct gpiod_descs obtained from gpiod_get_array() and can be

 * passed back to get/set array functions in order to activate fast processing

 * path if applicable.

 */

struct gpio_array;



/**

 * Struct containing an array of descriptors that can be obtained using

 * gpiod_get_array().

 */

struct gpio_descs {

	struct gpio_array *info;

	unsigned int ndescs;

	struct gpio_desc *desc[];

};

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