matroxfb returning incorrect fix.smem_len?

matroxfb returning incorrect fix.smem_len?

[Ian Romanick]

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While doing some work on the pci-rework branch of X.org, I noticed
something strange.  matroxfb correctly detects that my card has 16MiB,
but fix.smem_len is only 8MiB.

I looked around the matroxfb code and some of the other driver's code,
and I believe that matroxfb is incorrectly setting fix.smem_len.
Matroxfb sets fix.smem_len to (total_memory_size -
memory_used_by_current_mode).  Other drivers, such as nvidiafb do not do
this.

If folks agree that matroxfb is in error, I'll submit a patch.

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Re: matroxfb returning incorrect fix.smem_len?

[Geert Uytterhoeven]

On Wed, 28 Feb 2007, Ian Romanick wrote:
> While doing some work on the pci-rework branch of X.org, I noticed
> something strange.  matroxfb correctly detects that my card has 16MiB,
> but fix.smem_len is only 8MiB.
> 
> I looked around the matroxfb code and some of the other driver's code,
> and I believe that matroxfb is incorrectly setting fix.smem_len.
> Matroxfb sets fix.smem_len to (total_memory_size -
> memory_used_by_current_mode).  Other drivers, such as nvidiafb do not do
> this.

Did matroxfb detect a dual-head capable card?

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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Re: matroxfb returning incorrect fix.smem_len?

[Ian Romanick]

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Geert Uytterhoeven wrote:
> On Wed, 28 Feb 2007, Ian Romanick wrote:
>> While doing some work on the pci-rework branch of X.org, I noticed
>> something strange.  matroxfb correctly detects that my card has 16MiB,
>> but fix.smem_len is only 8MiB.
>>
>> I looked around the matroxfb code and some of the other driver's code,
>> and I believe that matroxfb is incorrectly setting fix.smem_len.
>> Matroxfb sets fix.smem_len to (total_memory_size -
>> memory_used_by_current_mode).  Other drivers, such as nvidiafb do not do
>> this.
> 
> Did matroxfb detect a dual-head capable card?

I did some more digging on this yesterday.  It seems that ydstorg.bytes
is always zero, so what I originally thought was the problem is not the
problem.

Looking at the logs, it looks like it is detecting my card as dual-head,
but it's not.  The weird thing is that I added a printk in
matroxfb_update_fix to show what smem_len is begin set to.  Before I
start X, it prints 16MiB twice.  As soon as X starts, it prints 8MiB and
returns that value to the X server.

I'm not quite sure what to make of that.
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Re: matroxfb returning incorrect fix.smem_len?

[Ville Syrjälä]

On Thu, Mar 01, 2007 at 08:47:34AM -0800, Ian Romanick wrote:
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> Hash: SHA1
> 
> Geert Uytterhoeven wrote:
> > On Wed, 28 Feb 2007, Ian Romanick wrote:
> >> While doing some work on the pci-rework branch of X.org, I noticed
> >> something strange.  matroxfb correctly detects that my card has 16MiB,
> >> but fix.smem_len is only 8MiB.
> >>
> >> I looked around the matroxfb code and some of the other driver's code,
> >> and I believe that matroxfb is incorrectly setting fix.smem_len.
> >> Matroxfb sets fix.smem_len to (total_memory_size -
> >> memory_used_by_current_mode).  Other drivers, such as nvidiafb do not do
> >> this.
> > 
> > Did matroxfb detect a dual-head capable card?
> 
> I did some more digging on this yesterday.  It seems that ydstorg.bytes
> is always zero, so what I originally thought was the problem is not the
> problem.
> 
> Looking at the logs, it looks like it is detecting my card as dual-head,
> but it's not.  The weird thing is that I added a printk in
> matroxfb_update_fix to show what smem_len is begin set to.  Before I
> start X, it prints 16MiB twice.  As soon as X starts, it prints 8MiB and
> returns that value to the X server.
> 
> I'm not quite sure what to make of that.

IIRC someone using DirectFB noticed something similar. I didn't bother 
investigating it much though.

Also matroxfb will never report > 16MB. We have a patch in DirectFB to 
fix that but IIRC it was not accepted into matroxfb because the matroxfb 
accel code can't actually handle it.

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

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