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gpiolib: Identify arrays matching GPIO hardware

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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: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Janusz Krzysztofik 2018-09-05 23:50:06 +02:00 committed by Linus Walleij
parent b9762bebc6
commit bf9346f5d4
4 changed files with 92 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

4
Documentation/driver-api/gpio/consumer.rst
View file

@ -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[];
}

72
drivers/gpio/gpiolib.c
View file

@ -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);

9
drivers/gpio/gpiolib.h
View file

@ -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,

9
include/linux/gpio/consumer.h
View file

@ -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[];
};