Some displays have dimensions that are not multiple of eight, for example
height of 36, but the driver divided the dimensions by 8. Defining display
to the next multiple of 8 is not good as then the display registers get
configured to dimensions that do not match. This contradicts intructions
by some display manufacturers.
Use DIV_ROUND_UP to multiple of 8 when needed so correct values can be
used.
The ssd1307fb_update_display bit reordering receives a simplification in
the process.
Signed-off-by: Marko Kohtala <marko.koht...@okoko.fi>
---
drivers/video/fbdev/ssd1307fb.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 86f2b79f3ed5..4f4a1b99d17d 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -151,10 +151,11 @@ static void ssd1307fb_update_display(struct ssd1307fb_par
*par)
{
struct ssd1307fb_array *array;
u8 *vmem = par->info->screen_buffer;
+ unsigned int line_length = par->info->fix.line_length;
+ unsigned int pages = DIV_ROUND_UP(par->height, 8);
int i, j, k;
- array = ssd1307fb_alloc_array(par->width * par->height / 8,
- SSD1307FB_DATA);
+ array = ssd1307fb_alloc_array(par->width * pages, SSD1307FB_DATA);
if (!array)
return;
@@ -187,22 +188,24 @@ static void ssd1307fb_update_display(struct ssd1307fb_par
*par)
* (5) A4 B4 C4 D4 E4 F4 G4 H4
*/
- for (i = 0; i < (par->height / 8); i++) {
+ for (i = 0; i < pages; i++) {
for (j = 0; j < par->width; j++) {
+ int m = 8;
u32 array_idx = i * par->width + j;
array->data[array_idx] = 0;
- for (k = 0; k < 8; k++) {
- u32 page_length = par->width * i;
- u32 index = page_length + (par->width * k + j)
/ 8;
- u8 byte = *(vmem + index);
- u8 bit = byte & (1 << (j % 8));
- bit = bit >> (j % 8);
+ /* Last page may be partial */
+ if (i + 1 == pages && par->height % 8)
+ m = par->height % 8;
+ 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;
}
}
}
- ssd1307fb_write_array(par->client, array, par->width * par->height / 8);
+ ssd1307fb_write_array(par->client, array, par->width * pages);
kfree(array);
}
@@ -438,7 +441,8 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
return ret;
ret = ssd1307fb_write_cmd(par->client,
- par->page_offset + (par->height / 8) - 1);
+ par->page_offset +
+ DIV_ROUND_UP(par->height, 8) - 1);
if (ret < 0)
return ret;
@@ -618,7 +622,7 @@ static int ssd1307fb_probe(struct i2c_client *client,
par->dclk_div = par->device_info->default_dclk_div;
par->dclk_frq = par->device_info->default_dclk_frq;
- vmem_size = par->width * par->height / 8;
+ vmem_size = DIV_ROUND_UP(par->width, 8) * par->height;
vmem = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
get_order(vmem_size));
@@ -641,7 +645,7 @@ static int ssd1307fb_probe(struct i2c_client *client,
info->fbops = &ssd1307fb_ops;
info->fix = ssd1307fb_fix;
- info->fix.line_length = par->width / 8;
+ info->fix.line_length = DIV_ROUND_UP(par->width, 8);
info->fbdefio = ssd1307fb_defio;
info->var = ssd1307fb_var;
--
2.17.1
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