video: fbdev: ssd1307fb: Simplify ssd1307fb_update_display()

Simplify the nested loops to handle conversion from linear frame buffer
to ssd1307 page layout:
  1. Move last page handling one level up, as the value of "m" is the
     same inside a page,
  2. array->data[] is filled linearly, so there is no need to
     recalculate array_idx over and over again; a simple increment is
     sufficient.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210727134730.3765898-3-geert@linux-m68k.org

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index e6b6263..6d7bd02 100644 (file)
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -158,6 +158,7 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par)
        u8 *vmem = par->info->screen_buffer;
        unsigned int line_length = par->info->fix.line_length;
        unsigned int pages = DIV_ROUND_UP(par->height, 8);
+       u32 array_idx = 0;
        int ret, i, j, k;
 
        array = ssd1307fb_alloc_array(par->width * pages, SSD1307FB_DATA);
@@ -194,19 +195,21 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par)
         */
 
        for (i = 0; i < pages; i++) {
+               int m = 8;
+
+               /* Last page may be partial */
+               if (i + 1 == pages && par->height % 8)
+                       m = par->height % 8;
                for (j = 0; j < par->width; j++) {
-                       int m = 8;
-                       u32 array_idx = i * par->width + j;
-                       array->data[array_idx] = 0;
-                       /* Last page may be partial */
-                       if (i + 1 == pages && par->height % 8)
-                               m = par->height % 8;
+                       u8 data = 0;
+
                        for (k = 0; k < m; k++) {
                                u8 byte = vmem[(8 * i + k) * line_length +
                                               j / 8];
                                u8 bit = (byte >> (j % 8)) & 1;
-                               array->data[array_idx] |= bit << k;
+                               data |= bit << k;
                        }
+                       array->data[array_idx++] = data;
                }
        }