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: Janusz Krzysztofik <jmkrzyszt@gmail.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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@ -109,9 +109,11 @@ For a function using multiple GPIOs all of those can be obtained with one call::
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enum gpiod_flags flags)
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This function returns a struct gpio_descs which contains an array of
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descriptors::
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descriptors. It also contains a pointer to a gpiolib private structure which,
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if passed back to get/set array functions, may speed up I/O proocessing::
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struct gpio_descs {
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struct gpio_array *info;
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unsigned int ndescs;
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struct gpio_desc *desc[];
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}
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@ -4174,7 +4174,9 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
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{
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struct gpio_desc *desc;
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struct gpio_descs *descs;
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int count;
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struct gpio_array *array_info = NULL;
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struct gpio_chip *chip;
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int count, bitmap_size;
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count = gpiod_count(dev, con_id);
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if (count < 0)
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@ -4190,9 +4192,77 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
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gpiod_put_array(descs);
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return ERR_CAST(desc);
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}
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descs->desc[descs->ndescs] = desc;
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chip = gpiod_to_chip(desc);
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/*
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* Select a chip of first array member
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* whose index matches its pin hardware number
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* as a candidate for fast bitmap processing.
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*/
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if (!array_info && gpio_chip_hwgpio(desc) == descs->ndescs) {
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struct gpio_descs *array;
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bitmap_size = BITS_TO_LONGS(chip->ngpio > count ?
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chip->ngpio : count);
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array = kzalloc(struct_size(descs, desc, count) +
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struct_size(array_info, invert_mask,
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3 * bitmap_size), GFP_KERNEL);
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if (!array) {
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gpiod_put_array(descs);
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return ERR_PTR(-ENOMEM);
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}
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memcpy(array, descs,
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struct_size(descs, desc, descs->ndescs + 1));
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kfree(descs);
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descs = array;
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array_info = (void *)(descs->desc + count);
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array_info->get_mask = array_info->invert_mask +
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bitmap_size;
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array_info->set_mask = array_info->get_mask +
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bitmap_size;
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array_info->desc = descs->desc;
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array_info->size = count;
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array_info->chip = chip;
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bitmap_set(array_info->get_mask, descs->ndescs,
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count - descs->ndescs);
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bitmap_set(array_info->set_mask, descs->ndescs,
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count - descs->ndescs);
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descs->info = array_info;
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}
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/*
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* Unmark members which don't qualify for fast bitmap
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* processing (different chip, not in hardware order)
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*/
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if (array_info && (chip != array_info->chip ||
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gpio_chip_hwgpio(desc) != descs->ndescs)) {
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__clear_bit(descs->ndescs, array_info->get_mask);
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__clear_bit(descs->ndescs, array_info->set_mask);
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} else if (array_info) {
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/* Exclude open drain or open source from fast output */
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if (gpiochip_line_is_open_drain(chip, descs->ndescs) ||
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gpiochip_line_is_open_source(chip, descs->ndescs))
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__clear_bit(descs->ndescs,
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array_info->set_mask);
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/* Identify 'fast' pins which require invertion */
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if (gpiod_is_active_low(desc))
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__set_bit(descs->ndescs,
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array_info->invert_mask);
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}
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descs->ndescs++;
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}
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if (array_info)
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dev_dbg(dev,
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"GPIO array info: chip=%s, size=%d, get_mask=%lx, set_mask=%lx, invert_mask=%lx\n",
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array_info->chip->label, array_info->size,
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*array_info->get_mask, *array_info->set_mask,
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*array_info->invert_mask);
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return descs;
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}
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EXPORT_SYMBOL_GPL(gpiod_get_array);
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@ -183,6 +183,15 @@ static inline bool acpi_can_fallback_to_crs(struct acpi_device *adev,
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}
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#endif
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struct gpio_array {
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struct gpio_desc **desc;
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unsigned int size;
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struct gpio_chip *chip;
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unsigned long *get_mask;
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unsigned long *set_mask;
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unsigned long invert_mask[];
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};
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struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip, u16 hwnum);
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int gpiod_get_array_value_complex(bool raw, bool can_sleep,
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unsigned int array_size,
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@ -17,11 +17,20 @@ struct device;
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*/
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struct gpio_desc;
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/**
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* Opaque descriptor for a structure of GPIO array attributes. This structure
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* is attached to struct gpiod_descs obtained from gpiod_get_array() and can be
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* passed back to get/set array functions in order to activate fast processing
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* path if applicable.
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*/
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struct gpio_array;
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/**
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* Struct containing an array of descriptors that can be obtained using
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* gpiod_get_array().
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*/
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struct gpio_descs {
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struct gpio_array *info;
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unsigned int ndescs;
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struct gpio_desc *desc[];
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};
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