Re: [PATCH resend 4/5] video: fbdev: ssd1307fb: Optimize screen updates
On Tue, Jul 20, 2021 at 11:16:27AM +0200, Geert Uytterhoeven wrote:
> Hi Sam,
>
> On Tue, Jul 20, 2021 at 9:56 AM Geert Uytterhoeven
> wrote:
> > On Mon, Jul 19, 2021 at 9:21 PM Sam Ravnborg 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
> >
> > > > --- 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);
Yep, then I would not be fooled so easy.
Sam
Re: [PATCH resend 4/5] video: fbdev: ssd1307fb: Optimize screen updates
Hi Sam,
On Tue, Jul 20, 2021 at 9:56 AM Geert Uytterhoeven wrote:
> On Mon, Jul 19, 2021 at 9:21 PM Sam Ravnborg 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
>
> > > --- 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 -- ge...@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
Re: [PATCH resend 4/5] video: fbdev: ssd1307fb: Optimize screen updates
Hi Sam,
On Mon, Jul 19, 2021 at 9:21 PM Sam Ravnborg 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
> > --- 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 -- There's lots of Linux beyond ia32 -- ge...@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
Re: [PATCH resend 4/5] video: fbdev: ssd1307fb: Optimize screen updates
Hi Geert,
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
> ---
> drivers/video/fbdev/ssd1307fb.c | 43 -
> 1 file changed, 26 insertions(+), 17 deletions(-)
>
> 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);
Add () like this - at least it helps me:
> + 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;
As before, this looks wrong to me.
Sam
> - 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,
> -
[PATCH resend 4/5] 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 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
---
drivers/video/fbdev/ssd1307fb.c | 43 -
1 file changed, 26 insertions(+), 17 deletions(-)
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)
--
2.25.1
