[Savage40] Long-Standing Bug

[Alex Deucher]

--- Tim Roberts <timr at probo.com> wrote:

> Alex Deucher wrote:
> 
> >--- Tim Roberts <timr at probo.com> wrote:
> >
> >  
> >
> >>The problem happens when you try to display a gradient background
> >>with a window manager.  When you do so, you see obvious striping in
> the
> >>colors -- striping that you should not see at depth 24.  It looks
> as bad or 
> >>worse than depth 16.
> >>
> >I looked into this a little this weekend, but I didn't have much
> luck. 
> >It looks like the savages only have a 6 bit DAC, but I don't really
> see
> >anything else that looks too out of place.  I did notice that lots
> of
> >other drivers set a mem RAC for colormap setup, I don't know if the
> >savages needs one too or not.  I've never really messed with the
> >xf86colormap* stuff, so any pointers would be welcome.  Tim, do you
> >have a old copy of savage_driver.c prior to the break?  I'd be
> curious
> >to check it out.
> >  
> >
> 
> The Savages support a 6-bit CLUT mode for compatibility with the VGA,
> 
> but it should be set to 8-bit CLUT mode for the modes we use.  The
> 6-bit 
> mode uses the LOW-order 6-bits of the palette values; if that were
> set, 
> the colors would be way too dim.

I tried 8, but I got a palette that was WAY off (looks like depth 8). 
Is there a bit somewhere to toggle 6/8 bit CLUT mode?

> 
> The attached zip contains my archive of 1.1.23t and 1.1.25t.  I
> believe 
> the problem was introduced between those two.  There are two relevant
> 

Thanks, I'll take a look at them.

> changes: first, I set the number of palette bits to 8 instead of 6,
> but 
> that only affects depth 8. Next, I set CMAP_PALETTED_TRUECOLOR when 
> calling xf86HandleColormaps.  That turns on the xgamma extension and 
> allows the colormap to be programmed.

the current driver still sets the palette bits to 6 in all cases except
depth 8.  setting it to 8 does produces a very broken output (looks
like depth 8).  Is there a crtc bit somewhere to toggle the CLUT mode? 
I know on radeon hardware there is and the palette bits are set to 6 or
8 depending on what mode the CLUT is in.  Most other drivers seem to
set the palette bits to 6, but they may only have 6 bit CLUTs.

Alex



		
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