Re: atyfb h/vsync polarity

["Ville Syrjälä" <syrjala@sci.fi>]

On Thu, Jun 23, 2005 at 11:25:10AM +0200, Alexander Kern wrote:
> Am Mittwoch, 22. Juni 2005 16:08 schrieb Raphael Assenat:
> > Hi,
> > I am a Linux Sparc64 user, and recently I decided to switch from 2.4
> > kernel series to 2.6 series. Everything worked well, but I had trouble
> > getting the framebuffer console to work.
> >
> > In openboot, my monitor worked perfectly. But as soon as Linux
> > configured the framebuffer, my monitor would loose sync. I compared the
> > output given by fbset on the working configuration (2.4 kernel) and the
> > non-working configuration (2.6.12 kernel). Every setting was identical,
> > except that the output on 2.4 had 'hsync high'. I tried 'fbset -hsync
> > high', but the screen still did not sync, and fbset still did not report
> > 'hsync high', as if the setting was ignored.
> >
> > After digging a little bit, I found this in
> > drivers/video/aty/atyfb_base.c:
> >
> > if(vdisplay < 400) {
> > 		h_sync_pol = 1;
> > 		v_sync_pol = 0;
> > } else if(vdisplay < 480) {
> > 		h_sync_pol = 0;
> > 		v_sync_pol = 1;
> > } else if(vdisplay < 768) {
> > 		h_sync_pol = 0;
> > 		v_sync_pol = 0;
> > } else {
> > 		h_sync_pol = 1;
> > 		v_sync_pol = 1;
> > }
> >
> > So no mater what sync polarity we ask for, the driver overrides them. I
> > commented the code above in my build, and the framebuffer console finally
> > works.
> >
> > It seems strange to me that the driver ignores the sync polarity we
> > request, but I'm sure the above code exists for a good reason so I would
> > not suggest to simply remove it as a fix. Can anyone explain why this code
> > is
> > necessary?
> this behaviour is from XFree code and more VGA like.

I don't think this sort of code really belongs in atyfb. If someone wants 
to follow this rule he can simply use modelines with the appropriate sync 
polarities.

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/


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