[PATCH 5/8] mtd: maps: gpio-addr-flash: Replace array with an integer

[Ricardo Ribalda Delgado]

By replacing the array with an integer we can avoid completely
the bit comparison loop if the value has not changed (by far
the most common case).

Signed-off-by: Ricardo Ribalda Delgado <ricardo.riba...@gmail.com>
---
 drivers/mtd/maps/gpio-addr-flash.c | 31 +++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/drivers/mtd/maps/gpio-addr-flash.c 
b/drivers/mtd/maps/gpio-addr-flash.c
index 22e100f07112..8f5e3dce9be3 100644
--- a/drivers/mtd/maps/gpio-addr-flash.c
+++ b/drivers/mtd/maps/gpio-addr-flash.c
@@ -43,7 +43,7 @@ struct async_state {
        struct map_info map;
        size_t gpio_count;
        unsigned *gpio_addrs;
-       int *gpio_values;
+       unsigned int gpio_values;
        unsigned int win_order;
 };
 #define gf_map_info_to_state(mi) ((struct async_state *)(mi)->map_priv_1)
@@ -55,22 +55,25 @@ struct async_state {
  *
  * Rather than call the GPIO framework every time, cache the last-programmed
  * value.  This speeds up sequential accesses (which are by far the most common
- * type).  We rely on the GPIO framework to treat non-zero value as high so
- * that we don't have to normalize the bits.
+ * type).
  */
 static void gf_set_gpios(struct async_state *state, unsigned long ofs)
 {
-       size_t i = 0;
-       int value;
+       int i;
 
        ofs >>= state->win_order;
-       do {
-               value = ofs & (1 << i);
-               if (state->gpio_values[i] != value) {
-                       gpio_set_value(state->gpio_addrs[i], value);
-                       state->gpio_values[i] = value;
-               }
-       } while (++i < state->gpio_count);
+
+       if (ofs == state->gpio_values)
+               return;
+
+       for (i = 0; i < state->gpio_count; i++) {
+               if ((ofs & BIT(i)) == (state->gpio_values & BIT(i)))
+                       continue;
+
+               gpio_set_value(state->gpio_addrs[i], !!(ofs & BIT(i)));
+       }
+
+       state->gpio_values = ofs;
 }
 
 /**
@@ -215,7 +218,7 @@ static int gpio_flash_probe(struct platform_device *pdev)
        if (!memory || !gpios || !gpios->end)
                return -EINVAL;
 
-       arr_size = sizeof(int) * gpios->end;
+       arr_size = sizeof(state->gpio_addrs[0]) * gpios->end;
        state = devm_kzalloc(&pdev->dev, sizeof(*state) + arr_size, GFP_KERNEL);
        if (!state)
                return -ENOMEM;
@@ -226,9 +229,7 @@ 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_order      = get_bitmask_order(resource_size(memory)) - 1;
-       memset(state->gpio_values, 0xff, arr_size);
 
        state->map.name       = DRIVER_NAME;
        state->map.read       = gf_read;
-- 
2.18.0