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video: ssd1307fb: Speed up the communication with the controller 

The code until now was sending only 1pixel-wide page segment at once,
and started a new transfer every time. It has proven very inefficient,
because for one byte to display on the screen, we had to actually send 3
bytes over I2C: the address, the type of data that was going to the
controller, and then the actual data.

This patches changes that by sending a whole page at once, avoiding most
of this expensive overhead.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
This commit is contained in:
Maxime Ripard 2013-04-22 12:02:24 +02:00 committed by Tomi Valkeinen
parent 9f7714d463
commit 3394e645a8
1 changed files with 8 additions and 3 deletions
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11
drivers/video/ssd1307fb.c
View File

@ -168,23 +168,28 @@ static void ssd1307fb_update_display(struct ssd1307fb_par *par)
*/
for (i = 0; i < (par->height / 8); i++) {
struct ssd1307fb_array *array;
ssd1307fb_write_cmd(par->client,
SSD1307FB_START_PAGE_ADDRESS + i + par->page_offset);
ssd1307fb_write_cmd(par->client, 0x00);
ssd1307fb_write_cmd(par->client, 0x10);
array = ssd1307fb_alloc_array(par->width, SSD1307FB_DATA);
for (j = 0; j < par->width; j++) {
u8 buf = 0;
array->data[j] = 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);
buf |= bit << k;
array->data[j] |= bit << k;
}
ssd1307fb_write_data(par->client, buf);
}
ssd1307fb_write_array(par->client, array, par->width);
kfree(array);
}
}