On Sun, 2009-11-01 at 17:59 -0500, Andy Walls wrote:
> On Sun, 2009-11-01 at 13:10 -0500, Brandon Jenkins wrote:
> > Hi Andy,
> >
> > The panic happens upon reboot and it is only 1 line of text oddly shifted.
> >
> > Kernel panic - not syncing: DMA: Memory would be corrupted
> >
> > If I switch back to the current v4l-dvb drivers no issue. To switch
> > back I have to boot from a USB drive.
>
> Brandon,
>
> Eww. OK. Nevermind performing any more data collection. I'm going to
> use a new strategy (when I find the time).
I forgot to mention that the panic you are running into is in the
Software IO Memory Managment Unit Translate Look-aside Buffer (SW IOMMU
TLB) in
linux/lib/swiotlb.c
Your machine must not have a hardware IO MMU (and mine must).
The software IOMMU is trying to allocate a bounce buffer for DMA and it
can't get one of the needed size (i.e. 607.5 kB) and the fallback static
buffer isn't big enough either (it is only 32 kB). That's why the panic
happens.
This certainly means that, in the general linux user case, very large
DMA buffers are bad.
So now I know....
Regards,
Andy
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