Re: [PATCH/RFC v2] video: fbdev: atari: Fix TT High video mode

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Andreas,

On Sun, Nov 1, 2020 at 1:47 PM Andreas Schwab <schwab@linux-m68k.org> wrote:
> On Nov 01 2020, Sam Ravnborg wrote:
> > On Sun, Nov 01, 2020 at 11:29:41AM +0100, Geert Uytterhoeven wrote:
> >> The horizontal resolution (640) for the TT High video mode (1280x960) is
> >> definitely bogus.  While fixing that, correct the timings to match the
> >> TTM195 service manual.
> >>
> >> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

> >> --- a/drivers/video/fbdev/atafb.c
> >> +++ b/drivers/video/fbdev/atafb.c
> >> @@ -495,8 +495,8 @@ static struct fb_videomode atafb_modedb[] __initdata = {
> >>              "tt-mid", 60, 640, 480, 31041, 120, 100, 8, 16, 140, 30,
> >>              0, FB_VMODE_NONINTERLACED | FB_VMODE_YWRAP
> >>      }, {
> >> -            /* 1280x960, 29 kHz, 60 Hz (TT high) */
> >> -            "tt-high", 57, 640, 960, 31041, 120, 100, 8, 16, 140, 30,
> >> +            /* 1280x960, 72 kHz, 72 Hz (TT high) */
> >> +            "tt-high", 57, 1280, 960, 7761, 260, 60, 36, 4, 192, 4,
> >>              0, FB_VMODE_NONINTERLACED | FB_VMODE_YWRAP
> >
> > Well-spotted. The change of 640 => 1280 is surely right.
> > I have a harder time understanding why the change of pixclock from 31041
> > to 7761 is correct. All other modes have a pixclock close to or equal
> > to 32000 - so it looks strange this one is off.
>
> According to the Profibuch the pixclock should be about 95000.

Please have a look at the paragraph on p. 1052, and realize that it
fails to take into account horizontal black/sync (the actual scan line
length is 1792 not 1280 pixels) (thanks, Michael!).

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