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    Subject[PATCH v2 4/8] mtd: maps: gpio-addr-flash: Use order insted of size
    Date
    By using the order of the window instead of the size, we can replace a
    lot of expensive division and modulus on the code with simple bit
    operations.

    Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
    ---
    drivers/mtd/maps/gpio-addr-flash.c | 39 ++++++++++++++++--------------
    1 file changed, 21 insertions(+), 18 deletions(-)

    diff --git a/drivers/mtd/maps/gpio-addr-flash.c b/drivers/mtd/maps/gpio-addr-flash.c
    index 54a0d7d2365a..22e100f07112 100644
    --- a/drivers/mtd/maps/gpio-addr-flash.c
    +++ b/drivers/mtd/maps/gpio-addr-flash.c
    @@ -25,6 +25,8 @@
    #include <linux/slab.h>
    #include <linux/types.h>

    +#define win_mask(x) ((BIT(x)) - 1)
    +
    #define DRIVER_NAME "gpio-addr-flash"

    /**
    @@ -34,7 +36,7 @@
    * @gpio_count: number of GPIOs used to address
    * @gpio_addrs: array of GPIOs to twiddle
    * @gpio_values: cached GPIO values
    - * @win_size: dedicated memory size (if no GPIOs)
    + * @win_order: dedicated memory size (if no GPIOs)
    */
    struct async_state {
    struct mtd_info *mtd;
    @@ -42,7 +44,7 @@ struct async_state {
    size_t gpio_count;
    unsigned *gpio_addrs;
    int *gpio_values;
    - unsigned long win_size;
    + unsigned int win_order;
    };
    #define gf_map_info_to_state(mi) ((struct async_state *)(mi)->map_priv_1)

    @@ -60,7 +62,8 @@ static void gf_set_gpios(struct async_state *state, unsigned long ofs)
    {
    size_t i = 0;
    int value;
    - ofs /= state->win_size;
    +
    + ofs >>= state->win_order;
    do {
    value = ofs & (1 << i);
    if (state->gpio_values[i] != value) {
    @@ -83,7 +86,7 @@ static map_word gf_read(struct map_info *map, unsigned long ofs)

    gf_set_gpios(state, ofs);

    - word = readw(map->virt + (ofs % state->win_size));
    + word = readw(map->virt + (ofs & win_mask(state->win_order)));
    test.x[0] = word;
    return test;
    }
    @@ -105,14 +108,14 @@ static void gf_copy_from(struct map_info *map, void *to, unsigned long from, ssi
    int this_len;

    while (len) {
    - if ((from % state->win_size) + len > state->win_size)
    - this_len = state->win_size - (from % state->win_size);
    - else
    - this_len = len;
    + this_len = from & win_mask(state->win_order);
    + this_len = BIT(state->win_order) - this_len;
    + this_len = min_t(int, len, this_len);

    gf_set_gpios(state, from);
    - memcpy_fromio(to, map->virt + (from % state->win_size),
    - this_len);
    + memcpy_fromio(to,
    + map->virt + (from & win_mask(state->win_order)),
    + this_len);
    len -= this_len;
    from += this_len;
    to += this_len;
    @@ -132,7 +135,7 @@ static void gf_write(struct map_info *map, map_word d1, unsigned long ofs)
    gf_set_gpios(state, ofs);

    d = d1.x[0];
    - writew(d, map->virt + (ofs % state->win_size));
    + writew(d, map->virt + (ofs & win_mask(state->win_order)));
    }

    /**
    @@ -152,13 +155,13 @@ static void gf_copy_to(struct map_info *map, unsigned long to,
    int this_len;

    while (len) {
    - if ((to % state->win_size) + len > state->win_size)
    - this_len = state->win_size - (to % state->win_size);
    - else
    - this_len = len;
    + this_len = to & win_mask(state->win_order);
    + this_len = BIT(state->win_order) - this_len;
    + this_len = min_t(int, len, this_len);

    gf_set_gpios(state, to);
    - memcpy_toio(map->virt + (to % state->win_size), from, len);
    + memcpy_toio(map->virt + (to & win_mask(state->win_order)),
    + from, len);

    len -= this_len;
    to += this_len;
    @@ -224,7 +227,7 @@ static int gpio_flash_probe(struct platform_device *pdev)
    state->gpio_count = gpios->end;
    state->gpio_addrs = (void *)(unsigned long)gpios->start;
    state->gpio_values = (void *)(state + 1);
    - state->win_size = resource_size(memory);
    + state->win_order = get_bitmask_order(resource_size(memory)) - 1;
    memset(state->gpio_values, 0xff, arr_size);

    state->map.name = DRIVER_NAME;
    @@ -233,7 +236,7 @@ static int gpio_flash_probe(struct platform_device *pdev)
    state->map.write = gf_write;
    state->map.copy_to = gf_copy_to;
    state->map.bankwidth = pdata->width;
    - state->map.size = state->win_size * (1 << state->gpio_count);
    + state->map.size = BIT(state->win_order + state->gpio_count);
    state->map.virt = devm_ioremap_resource(&pdev->dev, memory);
    if (IS_ERR(state->map.virt)) {
    dev_err(&pdev->dev, "failed to map memory\n");
    --
    2.18.0
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