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    Subject[PATCH v6 2/4] gpiolib: Identify arrays matching GPIO hardware
    Date
    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>
    ---
    Documentation/driver-api/gpio/consumer.rst | 4 +-
    drivers/gpio/gpiolib.c | 72 +++++++++++++++++++++++++++++-
    drivers/gpio/gpiolib.h | 9 ++++
    include/linux/gpio/consumer.h | 9 ++++
    4 files changed, 92 insertions(+), 2 deletions(-)

    diff --git a/Documentation/driver-api/gpio/consumer.rst b/Documentation/driver-api/gpio/consumer.rst
    index ed68042ddccf..7e0298b9a7b9 100644
    --- a/Documentation/driver-api/gpio/consumer.rst
    +++ b/Documentation/driver-api/gpio/consumer.rst
    @@ -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[];
    }
    diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
    index f0e9ffa8cab6..c1ed1c759345 100644
    --- a/drivers/gpio/gpiolib.c
    +++ b/drivers/gpio/gpiolib.c
    @@ -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);
    diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
    index 11e83d2eef89..b60905d558b1 100644
    --- a/drivers/gpio/gpiolib.h
    +++ b/drivers/gpio/gpiolib.h
    @@ -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,
    diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
    index 1b21dc7b0fad..8dede3e886af 100644
    --- a/include/linux/gpio/consumer.h
    +++ b/include/linux/gpio/consumer.h
    @@ -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[];
    };
    --
    2.16.4
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