On Fri, Nov 30, 2001 at 09:17:07AM -0700, Derrik Pates wrote:
> On Fri, 30 Nov 2001, Gareth Hughes wrote:
>
> > If I remember correctly, the hardware requires pitches to be multiples
> > of 64 (that's pixels, not bytes). It's been a while, but we don't do
> > that sort of thing for nothing...
>
> Well, how would an 800x600 display work on it then? The iBook's display is
> 800x600, and as it works now (the 64 X pScrn->bitsPerPixel value) the X
> server always gets the wrong line pitch (832) because 800 is not a round
> multiple of 64. With the existing code, the X server has to be forced into
> doing the "right" thing. With my change, it does the right thing
> completely by itself.
>
> I don't have the Rage128 docs, I can only tell you what I'm seeing here -
> and that's what I'm seeing. If the docs claim that the line pitch must be
> a multiple of 64 pixels, maybe the docs are incorrect. (Would it be the
> first time?)
I'm not familiar with your problem, or your proposed fix.
Two things, however:
1) These pitches may have nothing to do with the current mode. Mode
initialization probably touches different registers.
2) If the pitch register looks like this, say:
Bits Field
0 - 12 Pitch, in multiples of 64 pixels
... ...
(and I seem to remember that all the ATI cards look like this), then
there is no way to program a pitch that *isn't* a multiple of 64
pixels. Hence:
/* Offset in multiples of some large number. Radeon has
* 4k alignment, from memory -- something large in any case.
*/
hw_offset = real_offset / 4096;
/* Pitch in multiples of 64 pixels.
*/
hw_pitch = real_pitch / 64;
reg.src_pitch_offset = ((hw_pitch << 0) |
(hw_offset << 12));
Of course, it's been almost a year since I worked on that part of the
driver, so I may be completely wrong.
Note that even though a surface is allocated with a pitch that is a
multiple of 64 pixels (832 in this case), the RAMDAC may only scan out
the first 800 pixels or whatever the current mode is set to.
-- Gareth
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