[PATCH v2 5/5] video: fbdev: ssd1307fb: Cache address ranges

[Geert Uytterhoeven]

Cache the column and page ranges, to avoid doing unneeded I2C transfers
when the values haven't changed.

Signed-off-by: Geert Uytterhoeven <ge...@linux-m68k.org>
Acked-by: Sam Ravnborg <s...@ravnborg.org>
---
v2:
  - Add Acked-by,
  - Rebase.
---
 drivers/video/fbdev/ssd1307fb.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 9aed5ee0094f2d95..1e2f71c2f8a8bc78 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -82,6 +82,11 @@ struct ssd1307fb_par {
        struct regulator *vbat_reg;
        u32 vcomh;
        u32 width;
+       /* Cached address ranges */
+       u8 col_start;
+       u8 col_end;
+       u8 page_start;
+       u8 page_end;
 };
 
 struct ssd1307fb_array {
@@ -158,6 +163,9 @@ static int ssd1307fb_set_col_range(struct ssd1307fb_par 
*par, u8 col_start,
        u8 col_end = col_start + cols - 1;
        int ret;
 
+       if (col_start == par->col_start && col_end == par->col_end)
+               return 0;
+
        ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_COL_RANGE);
        if (ret < 0)
                return ret;
@@ -166,7 +174,13 @@ static int ssd1307fb_set_col_range(struct ssd1307fb_par 
*par, u8 col_start,
        if (ret < 0)
                return ret;
 
-       return ssd1307fb_write_cmd(par->client, col_end);
+       ret = ssd1307fb_write_cmd(par->client, col_end);
+       if (ret < 0)
+               return ret;
+
+       par->col_start = col_start;
+       par->col_end = col_end;
+       return 0;
 }
 
 static int ssd1307fb_set_page_range(struct ssd1307fb_par *par, u8 page_start,
@@ -175,6 +189,9 @@ static int ssd1307fb_set_page_range(struct ssd1307fb_par 
*par, u8 page_start,
        u8 page_end = page_start + pages - 1;
        int ret;
 
+       if (page_start == par->page_start && page_end == par->page_end)
+               return 0;
+
        ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_PAGE_RANGE);
        if (ret < 0)
                return ret;
@@ -183,7 +200,13 @@ static int ssd1307fb_set_page_range(struct ssd1307fb_par 
*par, u8 page_start,
        if (ret < 0)
                return ret;
 
-       return ssd1307fb_write_cmd(par->client, page_end);
+       ret = ssd1307fb_write_cmd(par->client, page_end);
+       if (ret < 0)
+               return ret;
+
+       par->page_start = page_start;
+       par->page_end = page_end;
+       return 0;
 }
 
 static int ssd1307fb_update_rect(struct ssd1307fb_par *par, unsigned int x,
-- 
2.25.1