[U-Boot] [PATCH v4 3/6] mcx: Disable DCACHE since USB EHCI is enabled

[Marek Vasut]

Dear Tom Rini,

> On 06/28/2012 03:36 PM, Marek Vasut wrote:
> > Dear Tom Rini,
> > 
> >> On Fri, Jun 29, 2012 at 12:01:58AM +0200, Marek Vasut wrote:
> >>> Dear Tom Rini,
> >>> 
> >>>> On 06/28/2012 07:37 AM, Marek Vasut wrote:
> >>>>> Dear Ilya Yanok,
> >>>>> 
> >>>>>> Dear Marek,
> >>>>>> 
> >>>>>> 28.06.2012 02:48, Marek Vasut wrote:
> >>>>>>>> Sorry for missing this discussion. I think compile-time disabling
> >>>>>>>> of the cache is too brutal.
> >>>>>>>> ehci-hcd cache handling is broken anyway: doing unaligned
> >>>>>>>> flushes/invalidates is a bug, and we know for sure that upper
> >>>>>>>> layers don't care about alignment (and I bet ehci-hcd does this
> >>>>>>>> even for its internal buffers). So what's the point in all this
> >>>>>>>> cache handling in ehci-hcd? It's not going to work anyway and
> >>>>>>>> just produces problems. So I suggest to just disable all this
> >>>>>>>> stuff until generic code will be fixed. Alternatively we can do
> >>>>>>>> bounce-buffering inside driver.
> >>>>>>> 
> >>>>>>> We should rather introduce generic bounce buffer. But the upper
> >>>>>>> layers are getting fixed recently so we should be getting there.
> >>>>>> 
> >>>>>> Really? Don't forget my old patch [1] then ;)
> >>>>>> Still I think we should rip off all the cache stuff from ehci-hcd
> >>>>>> until all patches for upper layers are included. Again, this stuff
> >>>>>> doesn't do proper things now anyway and USB won't work with dcache
> >>>>>> enabled.
> >>>>> 
> >>>>> Have you tested? I enabled dcache on m28 and tried asix ethernet
> >>>>> (needed a patch) and loading from ext2 and vfat (worked).
> >>>> 
> >>>> So then we have more places that accidentially aligned to 32bytes
> >>>> since this does not work on TI parts which require 64byte alignment.
> >>> 
> >>> Oh, this is very good it's broken. People actually started whining. Now
> >>> we have to wait until they start identifying the problematic places and
> >>> fixing them.
> >> 
> >> Uh-hunh.  So I guess for v2012.07 we'll build-time disable dcache for
> >> beagle and omap3_evm
> > 
> > Didn't you fix the issues?
> > 
> >> and leave it on for mcx and see who has time and
> >> hardware to fix things for v2012.10.
> > 
> > Or we fix it for mcx too until .07 is out ?
> 
> To clarify for everyone, the first part of this series fixes some
> alignment issues for things that were not starting address aligned.
> There still exist end-address alignment issues within ehci-hcd.  The
> time I have for this problem right now boils down to disable dcache for
> these boards so that USB is still functional.

To clarify it even further -- it always worked just by sheer coincidence ...

Best regards,
Marek Vasut