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SubjectRe: [RFC] Align tegra-ehci DMA transfers to 32B
On Fri, Dec 17, 2010 at 02:32:27PM -0800, Greg KH wrote:
> On Fri, Dec 17, 2010 at 01:58:47PM -0800, Robert Morell wrote:
> > This small set of patches fixes an issue where DMA from the tegra EHCI
> > controller could be corrupted. It was most commonly seen with USB network
> > adapters, though in theory it could happen with any USB traffic.
> >
> > (Note: An attempt was made to fix this with commit 367c3aab, which set
> > NET_IP_ALIGN to 0 and NET_SKB_PAD to 32. Unfortunately, not all network
> > drivers honor them (presumably since these are intended as optimizations rather
> > than hard rules). This does mean that properly-written network drivers should
> > fall through this code with very little overhead, however.)
> We don't have many USB network drivers, why not just fix them up to
> handle this properly, then you will not need to change any core USB
> code, right?

The USB core code is used by devices other than USB adapters. We've
only seen this problem so far with usbnet devices, but I can't test
every USB device ever to make sure that they always align their DMA to
32 bytes.


> thanks,
> greg k-h

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