Commit 251e48a1 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Sam Ravnborg
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video: fbdev: ssd1307fb: Optimize screen updates 



Currently, each screen update triggers an I2C transfer of all screen
data, up to 1 KiB of data for a 128x64 display, which takes at least 20
ms in Fast mode.

Reduce the amount of transferred data by only updating the rectangle
that changed.  Remove the calls to ssd1307fb_set_col_range() and
ssd1307fb_set_page_range() during initialization, as
ssd1307fb_update_rect() now takes care of that.

Note that for now the optimized operation is only used for fillrect,
copyarea, and imageblit, which are used by fbcon.

Signed-off-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: default avatarSam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210727134730.3765898-5-geert@linux-m68k.org
parent 8a15af3b

drivers/video/fbdev/ssd1307fb.c

+29 −21
Original line number Diff line number Diff line
@@ -186,16 +186,18 @@ static int ssd1307fb_set_page_range(struct ssd1307fb_par *par, u8 page_start, 
	return ssd1307fb_write_cmd(par->client, page_end);

}



static int ssd1307fb_update_display(struct ssd1307fb_par *par)

static int ssd1307fb_update_rect(struct ssd1307fb_par *par, unsigned int x,

				 unsigned int y, unsigned int width,

				 unsigned int height)

{

	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);

	unsigned int pages = DIV_ROUND_UP(y % 8 + height, 8);

	u32 array_idx = 0;

	int ret, i, j, k;



	array = ssd1307fb_alloc_array(par->width * pages, SSD1307FB_DATA);

	array = ssd1307fb_alloc_array(width * pages, SSD1307FB_DATA);

	if (!array)

		return -ENOMEM;
@@ -228,13 +230,21 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par) 
	 *  (5) A4 B4 C4 D4 E4 F4 G4 H4

	 */



	for (i = 0; i < pages; i++) {

	ret = ssd1307fb_set_col_range(par, par->col_offset + x, width);

	if (ret < 0)

		goto out_free;



	ret = ssd1307fb_set_page_range(par, par->page_offset + y / 8, pages);

	if (ret < 0)

		goto out_free;



	for (i = y / 8; i < y / 8 + pages; i++) {

		int m = 8;



		/* Last page may be partial */

		if (i + 1 == pages && par->height % 8)

		if (8 * (i + 1) > par->height)

			m = par->height % 8;

		for (j = 0; j < par->width; j++) {

		for (j = x; j < x + width; j++) {

			u8 data = 0;



			for (k = 0; k < m; k++) {
@@ -247,11 +257,17 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par) 
		}

	}



	ret = ssd1307fb_write_array(par->client, array, par->width * pages);

	ret = ssd1307fb_write_array(par->client, array, width * pages);



out_free:

	kfree(array);

	return ret;

}



static int ssd1307fb_update_display(struct ssd1307fb_par *par)

{

	return ssd1307fb_update_rect(par, 0, 0, par->width, par->height);

}



static ssize_t ssd1307fb_write(struct fb_info *info, const char __user *buf,

		size_t count, loff_t *ppos)
@@ -301,21 +317,24 @@ static void ssd1307fb_fillrect(struct fb_info *info, const struct fb_fillrect *r 
{

	struct ssd1307fb_par *par = info->par;

	sys_fillrect(info, rect);

	ssd1307fb_update_display(par);

	ssd1307fb_update_rect(par, rect->dx, rect->dy, rect->width,

			      rect->height);

}



static void ssd1307fb_copyarea(struct fb_info *info, const struct fb_copyarea *area)

{

	struct ssd1307fb_par *par = info->par;

	sys_copyarea(info, area);

	ssd1307fb_update_display(par);

	ssd1307fb_update_rect(par, area->dx, area->dy, area->width,

			      area->height);

}



static void ssd1307fb_imageblit(struct fb_info *info, const struct fb_image *image)

{

	struct ssd1307fb_par *par = info->par;

	sys_imageblit(info, image);

	ssd1307fb_update_display(par);

	ssd1307fb_update_rect(par, image->dx, image->dy, image->width,

			      image->height);

}



static const struct fb_ops ssd1307fb_ops = {
@@ -495,17 +514,6 @@ static int ssd1307fb_init(struct ssd1307fb_par *par) 
	if (ret < 0)

		return ret;



	/* Set column range */

	ret = ssd1307fb_set_col_range(par, par->col_offset, par->width);

	if (ret < 0)

		return ret;



	/* Set page range */

	ret = ssd1307fb_set_page_range(par, par->page_offset,

				       DIV_ROUND_UP(par->height, 8));

	if (ret < 0)

		return ret;



	/* Clear the screen */

	ret = ssd1307fb_update_display(par);

	if (ret < 0)