[U-Boot] Cache alignment warnings on Tegra (ARM)

Thierry Reding
2012-09-19T05:46:50Z

On Tue, Sep 18, 2012 at 11:20:30PM +0200, Marek Vasut wrote:
> Dear Thierry Reding,
>
> > On Tue, Sep 18, 2012 at 09:36:18PM +0200, Marek Vasut wrote:
> > > Dear Thierry Reding,
> > >
> > > [...]
> > >
> > > > > Sure, but after you apply the bounce buffer, you can safely
> > > > > invalidate the whole cacheline, so align it up and be done with it.
> > > >
> > > > That's what I proposed to do last time around but it was NAK'ed.
> > >
> > > By who?
> >
> > I think it was Simon Glass and Mike Frysinger. They NAK'ed it for very
> > valid reason, so I'm not complaining.
> >
> > > > At the
> > > > time I didn't ensure that the buffer was actually big enough, which is
> > > > why people didn't like it (data on the stack after the DMA buffer might
> > > > be invalidated as well).
> > >
> > > Correct, thus the bounce buffer.
> >
> > I don't think we even need the bounce buffer. All that needs to be done
> > is guarantee that the buffers passed to the MMC driver are properly
> > aligned and sized.
>
> If you resize the MMC structures and call sizeof() on them to get the size of
> the transfer, the MMC won't work correctly anymore.

That's exactly what my first attempt was back then. It was a very naive
attempt at getting the MMC core to pass the correct size and as you said
it didn't work.

Thierry
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