Mailinglist Archive: radeonhd (259 mails)

[Kunal Gangakhedkar <kunal.gangakhedkar@xxxxxxxxx>]

On Tuesday 03 Nov 2009 10:27:28 pm you wrote:
> On Tue, Nov 3, 2009 at 11:45 AM, Kunal Gangakhedkar
> <kunal.gangakhedkar@xxxxxxxxx> wrote:
> > On Tuesday 03 Nov 2009 8:38:55 pm Alex Deucher wrote:
> > > On Tue, Nov 3, 2009 at 10:00 AM, Kunal Gangakhedkar
> > > <kunal.gangakhedkar@xxxxxxxxx> wrote:
> > > > Hi,
> > > >
> > > > Sorry for not using word-wrap - so that the logs don't look messed up.
> > > >
> > > > I recently bought an HP Pavilion dv6 series laptop which comes with 
> > > > Mobility Radeon HD 4650 graphics chip with 1GB GDD3 VRAM.
> > > > It seems to be common with the dv6 series laptops from HP.
> > > >
> > > > The basic radeonhd X driver with the mainline radeon GPU driver gives me 
> > > > pretty nice X environment.
> > > > However, there are two issues that I'd like to know more about:
> > > >
> > > > 1.
> > > > the X.org logs show that the entire VRAM is not being used - instead 
> > > > only 256M out of the 1G are being used.
> > > >
> > > > The msg from Xorg.log is:
> > > > (II) RADEONHD(0): The detected amount of videoram exceeds the PCI BAR 
> > > > aperture.
> > > > (II) RADEONHD(0): Using only 262144kB of the total 1048576kB.
> > > > (--) RADEONHD(0): VideoRAM: 262144 kByte
> > > >
> > > > I'm attaching gzipped Xorg.0.log with this mail.
> > > > Even the lspci output (included below) says that the memory is 256M
> > > > whereas ATi catalyst driver in pre-installed Windows Vista Home Premium 
> > > > shows and uses full 1GB of VRAM.
> > >
> > > 256 MB is the max PCI aperture size.  that's the largest amount the
> > > CPU can access.  The GPU, however, can access the entire amount.
> > > Support for using the extended memory will come eventually with kms.
> >
> > But, shouldn't the X driver (xserver-xorg-video-radeonhd) report it 
> > correctly in Xorg.0.log?
> > Isn't that what drives the GPU (via the kernel-mode radeon drm driver)?
> > Just curious..
>
> It does report it:
> (II) RADEONHD(0): The detected amount of videoram exceeds the PCI BAR 
> aperture.
> (II) RADEONHD(0): Using only 262144kB of the total 1048576kB.
>
> However, the CPU can only map 256MB, so it caps vram at 256MB.  If the
> CPU needs to access vram, it's limited to 256MB.  For VRAM beyond the
> 256 MB aperture, the GPU is responsible for dealing with it since only
> it can access the full amount.  The hard part is dealing with buffers
> in extended memory that the CPU needs access to.  The GPU has to move
> the buffer to some place the CPU can access it.
>
> With kms, all asic setup and modesetting moves to the kernel.  The ddx
> at that point is only responsible for EXA/Xv acceleration and
> interfacing with X.
>
> Alex

Thanks a lot for the explanation - it was really helpful.. :)

Thanks,
Kunal
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