* Radeonfb hsync fudge factor?
@ 2003-12-23 23:43 John Zielinski
2003-12-24 1:42 ` Benjamin Herrenschmidt
2003-12-24 9:18 ` Sergey Vlasov
0 siblings, 2 replies; 6+ messages in thread
From: John Zielinski @ 2003-12-23 23:43 UTC (permalink / raw)
To: linux-fbdev-devel; +Cc: Benjamin Herrenschmidt
What's the hsync fudge factor used for?
I noticed that the left edged of my screen moved a bit when I was
switching between 32/16/8 bpp modes and tracked it down to this.
John
p.s. I have this urge to giggle every time I type in the words "fudge
factor" for some reason. :)
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Radeonfb hsync fudge factor?
2003-12-23 23:43 Radeonfb hsync fudge factor? John Zielinski
@ 2003-12-24 1:42 ` Benjamin Herrenschmidt
2003-12-24 9:18 ` Sergey Vlasov
1 sibling, 0 replies; 6+ messages in thread
From: Benjamin Herrenschmidt @ 2003-12-24 1:42 UTC (permalink / raw)
To: John Zielinski; +Cc: Linux Fbdev development list
On Wed, 2003-12-24 at 10:43, John Zielinski wrote:
> What's the hsync fudge factor used for?
>
> I noticed that the left edged of my screen moved a bit when I was
> switching between 32/16/8 bpp modes and tracked it down to this.
>
> John
>
> p.s. I have this urge to giggle every time I type in the words "fudge
> factor" for some reason. :)
I'm not too sure about why it's there, it comes from ATI code in
the first place.
Ben.
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Radeonfb hsync fudge factor?
2003-12-23 23:43 Radeonfb hsync fudge factor? John Zielinski
2003-12-24 1:42 ` Benjamin Herrenschmidt
@ 2003-12-24 9:18 ` Sergey Vlasov
2003-12-24 12:12 ` Geert Uytterhoeven
1 sibling, 1 reply; 6+ messages in thread
From: Sergey Vlasov @ 2003-12-24 9:18 UTC (permalink / raw)
To: linux-fbdev-devel
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On Tue, Dec 23, 2003 at 06:43:17PM -0500, John Zielinski wrote:
> What's the hsync fudge factor used for?
>
> I noticed that the left edged of my screen moved a bit when I was
> switching between 32/16/8 bpp modes and tracked it down to this.
The same thing here - both with Radeon VE QY and 8500LE (don't remember
the exact chip version). Adding the opposite value to the fbset
parameters puts the image back into the place - so it looks like the hsync
fudge is unneeded at least with these chipsets.
Probably this fudge factor was needed for some early chips?
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Radeonfb hsync fudge factor?
2003-12-24 9:18 ` Sergey Vlasov
@ 2003-12-24 12:12 ` Geert Uytterhoeven
2003-12-24 20:52 ` John Zielinski
0 siblings, 1 reply; 6+ messages in thread
From: Geert Uytterhoeven @ 2003-12-24 12:12 UTC (permalink / raw)
To: Sergey Vlasov; +Cc: Linux Frame Buffer Device Development
On Wed, 24 Dec 2003, Sergey Vlasov wrote:
> On Tue, Dec 23, 2003 at 06:43:17PM -0500, John Zielinski wrote:
> > What's the hsync fudge factor used for?
> >
> > I noticed that the left edged of my screen moved a bit when I was
> > switching between 32/16/8 bpp modes and tracked it down to this.
>
> The same thing here - both with Radeon VE QY and 8500LE (don't remember
> the exact chip version). Adding the opposite value to the fbset
> parameters puts the image back into the place - so it looks like the hsync
> fudge is unneeded at least with these chipsets.
>
> Probably this fudge factor was needed for some early chips?
Yep, Mach64 needs one (but atyfb doesn't take care of it yet). So if you switch
between depths, the display may shift horizontally. I guess this is due to
different lengths of the dataflow paths for different color depths.
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
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Radeonfb hsync fudge factor?
2003-12-24 12:12 ` Geert Uytterhoeven
@ 2003-12-24 20:52 ` John Zielinski
2003-12-24 21:00 ` Sergey Vlasov
0 siblings, 1 reply; 6+ messages in thread
From: John Zielinski @ 2003-12-24 20:52 UTC (permalink / raw)
To: Geert Uytterhoeven; +Cc: Sergey Vlasov, Linux Frame Buffer Device Development
Geert Uytterhoeven wrote:
>On Wed, 24 Dec 2003, Sergey Vlasov wrote:
>
>
>>Probably this fudge factor was needed for some early chips?
>>
>>
>
>Yep, Mach64 needs one (but atyfb doesn't take care of it yet). So if you switch
>between depths, the display may shift horizontally. I guess this is due to
>different lengths of the dataflow paths for different color depths.
>
>
How many cards handled by radeonfb need it? That way we can add a
fudge or nofudge driver option. Or put it in the card database if the
numbers are roughly equal.
I need to see if that's what's causing the sync problems with my friends
HDTV....
John
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Radeonfb hsync fudge factor?
2003-12-24 20:52 ` John Zielinski
@ 2003-12-24 21:00 ` Sergey Vlasov
0 siblings, 0 replies; 6+ messages in thread
From: Sergey Vlasov @ 2003-12-24 21:00 UTC (permalink / raw)
To: John Zielinski; +Cc: Geert Uytterhoeven, Linux Frame Buffer Device Development
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On Wed, Dec 24, 2003 at 03:52:57PM -0500, John Zielinski wrote:
> Geert Uytterhoeven wrote:
>
> >On Wed, 24 Dec 2003, Sergey Vlasov wrote:
> >
> >
> >>Probably this fudge factor was needed for some early chips?
> >>
> >>
> >
> >Yep, Mach64 needs one (but atyfb doesn't take care of it yet). So if you
> >switch
> >between depths, the display may shift horizontally. I guess this is due to
> >different lengths of the dataflow paths for different color depths.
> >
> >
>
> How many cards handled by radeonfb need it? That way we can add a
> fudge or nofudge driver option. Or put it in the card database if the
> numbers are roughly equal.
I suspect that either none of these cards need it (if this is really a
leftover from Mach64 days), or maybe some of the oldest (R100) cards
need it. Radeon VE QY (RV100) and 8500 QL (R200) certainly don't need
this fudge factor.
Does someone have an old R100-based card to test this?
> I need to see if that's what's causing the sync problems with my friends
> HDTV....
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2003-12-24 21:00 UTC | newest]
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2003-12-23 23:43 Radeonfb hsync fudge factor? John Zielinski
2003-12-24 1:42 ` Benjamin Herrenschmidt
2003-12-24 9:18 ` Sergey Vlasov
2003-12-24 12:12 ` Geert Uytterhoeven
2003-12-24 20:52 ` John Zielinski
2003-12-24 21:00 ` Sergey Vlasov
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