[ivtv-devel] cx18: YUV frame alignment improvements

Brandon Jenkins bcjenkins at tvwhere.com
Tue Nov 3 18:06:58 CET 2009


On Sun, Nov 1, 2009 at 6:15 PM, Andy Walls <awalls at radix.net> wrote:
> 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
>
>
Hi Andy,

How would I know if I have/don't have a HW IO MMU and maybe isn't
enabled correctly? Separately, I also have three cards running too.

Brandon



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