diff mbox series

[resend,4/5] video: fbdev: ssd1307fb: Optimize screen updates

Message ID 20210714145804.2530727-5-geert@linux-m68k.org (mailing list archive)
State Superseded, archived
Headers show
Series video: fbdev: ssd1307fb: Optimizations and improvements | expand

Commit Message

Geert Uytterhoeven July 14, 2021, 2:58 p.m. UTC 
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 call to ssd1307fb_set_address_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: Geert Uytterhoeven <geert@linux-m68k.org>
---
 drivers/video/fbdev/ssd1307fb.c | 43 ++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 17 deletions(-)

Comments

Geert Uytterhoeven July 20, 2021, 7:56 a.m. UTC | #1 
Hi Sam,

On Mon, Jul 19, 2021 at 9:21 PM Sam Ravnborg <sam@ravnborg.org> wrote:
> On Wed, Jul 14, 2021 at 04:58:03PM +0200, Geert Uytterhoeven wrote:
> > 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 call to ssd1307fb_set_address_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: Geert Uytterhoeven <geert@linux-m68k.org>

> > --- a/drivers/video/fbdev/ssd1307fb.c
> > +++ b/drivers/video/fbdev/ssd1307fb.c
> > @@ -184,16 +184,18 @@ static int ssd1307fb_set_address_range(struct ssd1307fb_par *par, u8 col_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(height + y % 8, 8);
>
> Add () like this - at least it helps me:
> > +     unsigned int pages = DIV_ROUND_UP((height + y) % 8, 8);

Thanks, that's actually a genuine bug.

> > @@ -226,13 +228,18 @@ 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_address_range(par, par->col_offset + x, width,
> > +                                       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;
> As before, this looks wrong to me.

Let's sort that out in the other thread...

Gr{oetje,eeting}s,

                        Geert
Geert Uytterhoeven July 20, 2021, 9:16 a.m. UTC | #2 
Hi Sam,

On Tue, Jul 20, 2021 at 9:56 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Mon, Jul 19, 2021 at 9:21 PM Sam Ravnborg <sam@ravnborg.org> wrote:
> > On Wed, Jul 14, 2021 at 04:58:03PM +0200, Geert Uytterhoeven wrote:
> > > 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 call to ssd1307fb_set_address_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: Geert Uytterhoeven <geert@linux-m68k.org>
>
> > > --- a/drivers/video/fbdev/ssd1307fb.c
> > > +++ b/drivers/video/fbdev/ssd1307fb.c
> > > @@ -184,16 +184,18 @@ static int ssd1307fb_set_address_range(struct ssd1307fb_par *par, u8 col_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(height + y % 8, 8);
> >
> > Add () like this - at least it helps me:
> > > +     unsigned int pages = DIV_ROUND_UP((height + y) % 8, 8);
>
> Thanks, that's actually a genuine bug.

No it's not "(height + y) % 8" is wrong.

Better if I reorder the operands like below?

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

Gr{oetje,eeting}s,

                        Geert
diff mbox series

Patch

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index cfa27ea0feab4f01..8e3d4be74723b9bf 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -184,16 +184,18 @@  static int ssd1307fb_set_address_range(struct ssd1307fb_par *par, u8 col_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(height + y % 8, 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;
 
@@ -226,13 +228,18 @@  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_address_range(par, par->col_offset + x, width,
+					  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++) {
@@ -245,11 +252,17 @@  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)
@@ -299,21 +312,24 @@  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 = {
@@ -493,13 +509,6 @@  static int ssd1307fb_init(struct ssd1307fb_par *par)
 	if (ret < 0)
 		return ret;
 
-	/* Set column and page range */
-	ret = ssd1307fb_set_address_range(par, par->col_offset, par->width,
-					  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)