Re: USB mass storage and ARM cache coherency

[Catalin Marinas <catalin.marinas@arm.com>]

On Tue, 2010-02-02 at 15:10 +0000, Andreas Mohr wrote:
> [added another __bzero coherency crash victim, see
> http://lkml.org/lkml/2008/6/9/14 ]
> 
> On Tue, Feb 02, 2010 at 03:52:19PM +0100, Oliver Neukum wrote:
> > Am Dienstag, 2. Februar 2010 15:42:49 schrieb Clemens Ladisch:
> > > > Or... usb-audio? I should have verified that it is using bulk endpoints
> > > > (and thus the patch applies to my case).
> > > > usb-audio probably uses isochronous transfers, thus that would be
> > > > an obvious reason why the patch didn't work for me.
> > >
> > > snd-usb-audio indeed uses isochronous transfers, but those buffers are
> > > never mapped into user space.  The intermediate vmalloc()ed buffer is,
> > > however, and there was a bugfix for this recently.  Do you have these
> > > patches in your tree?
> >
> > Now that I think about it, several video drivers do map it to user space.
> 
> OK, then the urb loop needs to also handle isochronous pipes,
> and IMHO we should have a generic helper for this instead of open-coding
> it, since it probably needs to be done in a couple affected HCDs
> (and, most importantly, only on affected architectures - which the helper
> could handle transparently).

I'm planning to send a proposal to linux-arch for a flush_dcache_range()
function.

-- 
Catalin