gpiolib: Implement fast processing path in get/set array
Certain GPIO descriptor arrays returned by gpio_get_array() may contain information on direct mapping of array members to pins of a single GPIO chip in hardware order. In such cases, bitmaps of values can be passed directly from/to the chip's .get/set_multiple() callbacks without wasting time on iterations. Add respective code to gpiod_get/set_array_bitmap_complex() functions. Pins not applicable for fast path are processed as before, skipping over the 'fast' ones. Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>4.20.x+fslc
Janusz Krzysztofik
Linus Walleij
parent
77588c14ac
commit
b17566a6b0
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@ -193,3 +193,18 @@ And the table can be added to the board code as follows::
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The line will be hogged as soon as the gpiochip is created or - in case the
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chip was created earlier - when the hog table is registered.
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Arrays of pins
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--------------
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In addition to requesting pins belonging to a function one by one, a device may
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also request an array of pins assigned to the function. The way those pins are
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mapped to the device determines if the array qualifies for fast bitmap
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processing. If yes, a bitmap is passed over get/set array functions directly
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between a caller and a respective .get/set_multiple() callback of a GPIO chip.
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In order to qualify for fast bitmap processing, the pin mapping must meet the
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following requirements:
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- it must belong to the same chip as other 'fast' pins of the function,
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- its index within the function must match its hardware number within the chip.
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Open drain and open source pins are excluded from fast bitmap output processing.
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@ -388,6 +388,14 @@ array_info should be set to NULL.
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Note that for optimal performance GPIOs belonging to the same chip should be
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contiguous within the array of descriptors.
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Still better performance may be achieved if array indexes of the descriptors
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match hardware pin numbers of a single chip. If an array passed to a get/set
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array function matches the one obtained from gpiod_get_array() and array_info
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associated with the array is also passed, the function may take a fast bitmap
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processing path, passing the value_bitmap argument directly to the respective
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.get/set_multiple() callback of the chip. That allows for utilization of GPIO
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banks as data I/O ports without much loss of performance.
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The return value of gpiod_get_array_value() and its variants is 0 on success
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or negative on error. Note the difference to gpiod_get_value(), which returns
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0 or 1 on success to convey the GPIO value. With the array functions, the GPIO
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@ -2789,7 +2789,36 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
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struct gpio_array *array_info,
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unsigned long *value_bitmap)
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{
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int i = 0;
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int err, i = 0;
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/*
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* Validate array_info against desc_array and its size.
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* It should immediately follow desc_array if both
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* have been obtained from the same gpiod_get_array() call.
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*/
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if (array_info && array_info->desc == desc_array &&
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array_size <= array_info->size &&
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(void *)array_info == desc_array + array_info->size) {
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if (!can_sleep)
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WARN_ON(array_info->chip->can_sleep);
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err = gpio_chip_get_multiple(array_info->chip,
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array_info->get_mask,
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value_bitmap);
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if (err)
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return err;
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if (!raw && !bitmap_empty(array_info->invert_mask, array_size))
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bitmap_xor(value_bitmap, value_bitmap,
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array_info->invert_mask, array_size);
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if (bitmap_full(array_info->get_mask, array_size))
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return 0;
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i = find_first_zero_bit(array_info->get_mask, array_size);
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} else {
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array_info = NULL;
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}
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while (i < array_size) {
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struct gpio_chip *chip = desc_array[i]->gdev->chip;
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@ -2820,7 +2849,12 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
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int hwgpio = gpio_chip_hwgpio(desc);
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__set_bit(hwgpio, mask);
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i++;
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if (array_info)
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find_next_zero_bit(array_info->get_mask,
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array_size, i);
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else
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i++;
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} while ((i < array_size) &&
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(desc_array[i]->gdev->chip == chip));
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@ -2831,7 +2865,7 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
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return ret;
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}
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for (j = first; j < i; j++) {
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for (j = first; j < i; ) {
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const struct gpio_desc *desc = desc_array[j];
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int hwgpio = gpio_chip_hwgpio(desc);
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int value = test_bit(hwgpio, bits);
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@ -2840,6 +2874,11 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
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value = !value;
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__assign_bit(j, value_bitmap, value);
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trace_gpio_value(desc_to_gpio(desc), 1, value);
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if (array_info)
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find_next_zero_bit(array_info->get_mask, i, j);
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else
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j++;
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}
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if (mask != fastpath)
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@ -3043,6 +3082,32 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
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{
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int i = 0;
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/*
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* Validate array_info against desc_array and its size.
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* It should immediately follow desc_array if both
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* have been obtained from the same gpiod_get_array() call.
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*/
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if (array_info && array_info->desc == desc_array &&
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array_size <= array_info->size &&
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(void *)array_info == desc_array + array_info->size) {
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if (!can_sleep)
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WARN_ON(array_info->chip->can_sleep);
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if (!raw && !bitmap_empty(array_info->invert_mask, array_size))
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bitmap_xor(value_bitmap, value_bitmap,
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array_info->invert_mask, array_size);
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gpio_chip_set_multiple(array_info->chip, array_info->set_mask,
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value_bitmap);
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if (bitmap_full(array_info->set_mask, array_size))
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return 0;
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i = find_first_zero_bit(array_info->set_mask, array_size);
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} else {
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array_info = NULL;
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}
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while (i < array_size) {
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struct gpio_chip *chip = desc_array[i]->gdev->chip;
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unsigned long fastpath[2 * BITS_TO_LONGS(FASTPATH_NGPIO)];
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@ -3070,7 +3135,14 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
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int hwgpio = gpio_chip_hwgpio(desc);
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int value = test_bit(i, value_bitmap);
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if (!raw && test_bit(FLAG_ACTIVE_LOW, &desc->flags))
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/*
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* Pins applicable for fast input but not for
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* fast output processing may have been already
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* inverted inside the fast path, skip them.
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*/
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if (!raw && !(array_info &&
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test_bit(i, array_info->invert_mask)) &&
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test_bit(FLAG_ACTIVE_LOW, &desc->flags))
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value = !value;
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trace_gpio_value(desc_to_gpio(desc), 0, value);
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/*
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@ -3089,7 +3161,12 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
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__clear_bit(hwgpio, bits);
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count++;
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}
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i++;
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if (array_info)
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find_next_zero_bit(array_info->set_mask,
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array_size, i);
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else
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i++;
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} while ((i < array_size) &&
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(desc_array[i]->gdev->chip == chip));
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/* push collected bits to outputs */
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