Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 20 Jul 2021 11:16:27 +0200 | Subject | Re: [PATCH resend 4/5] video: fbdev: ssd1307fb: Optimize screen updates |
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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
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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