On Wed, 2017-01-25 at 12:54 +0000, Robin Murphy wrote:
> On 25/01/17 12:51, Arnd Bergmann wrote:
> > On Wed, Jan 25, 2017 at 1:37 PM, Michael Zoran <mzoran@xxxxxxxxxxxx
> > > wrote:
> > > On Wed, 2017-01-25 at 12:03 +0000, Robin Murphy wrote:
> > > > hen bypassing SWIOTLB on small-memory systems, we need to avoid
> > > > calling
> > > > into swiotlb_dma_mapping_error() in exactly the same way as we
> > > > avoid
> > > > swiotlb_dma_supported(), because the former also relies on
> > > > SWIOTLB
> > > > state
> > > > being initialised.
> > >
> > > I didn't submit the initial ARM64 port of the RPI 3, so I don't
> > > know
> > > much about this. But from a third personal point of view, this
> > > seems
> > > to side step the main issue here.
> >
> > I think Robin's approach is fixing exactly the right part of the
> > code.
> >
> > > From an ARM64 subsystem point of view, what exactly is the
> > > correct/recommended method for ensuring the mm subsystem is
> > > initialized
> > > correctly?
> >
> > It is initialized correctly, the bug was calling the wrong helper
> > when swiotlb
> > is not used because we determined that we don't need it.
> >
> > One concern from inspection:
> >
> > > +static int __swiotlb_dma_mapping_error(struct device *hwdev,
> > > dma_addr_t addr)
> > > +{
> > > + if (swiotlb)
> > > + return swiotlb_dma_mapping_error(hwdev, addr);
> > > + return 1;
> > > +}
> >
> > Shouldn't that be
> >
> > return addr == DMA_ERROR_CODE;
> >
> > in the last line? Otherwise any addr is interpreted as an error,
> > which
> > seems wrong. Maybe I'm missing something obvious here.
>
> Aw crap, copy/paste/brain error - thanks.
>
> I'll have a nice strong cup of tea, actually engage thinking mode,
> and
> respin...
>
> Robin.
>
> >
> > Arnd
> >
I have an RPI 3 that I run in ARM64 mode all the time for personal use.
If/when you have a patch ready, I'm more then willing to try it out
locally.
Just tell me the path of the git tree and branch that it's based on.
Thanks.
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html