PL310 errata workarounds

[Marek Vasut]

On Wednesday, March 19, 2014 at 10:46:32 PM, Russell King - ARM Linux wrote:
> On Wed, Mar 19, 2014 at 04:35:58PM -0500, Rob Herring wrote:
> > On Wed, Mar 19, 2014 at 4:22 PM, Marek Vasut <marex at denx.de> wrote:
> > > On Friday, March 14, 2014 at 08:14:06 PM, Rob Herring wrote:
> > >> On Fri, Mar 14, 2014 at 12:57 PM, Russell King - ARM Linux
> > >> 
> > >> <linux at arm.linux.org.uk> wrote:
> > >> > On Fri, Mar 14, 2014 at 11:02:17AM -0500, Rob Herring wrote:
> > >> >> The obvious fix is to convert l2x0_flush_line to a function ptr
> > >> >> which just further complicates the code.
> > >> > 
> > >> > I currently regard this code as unmaintainable, so right now I'm in
> > >> > the process of completely rewriting it, going back to the specs and
> > >> > checking what is required.  Sharing code between the L210, L220 and
> > >> > L310 looks good from the point of view of keeping the line count
> > >> > down, but actually they're quite different and have various
> > >> > different requirements.
> > >> > 
> > >> > Out of those, L220 is the odd one out: all operations are background
> > >> > operations there, which means they have to be waited for. 
> > >> > Currently, if you have one of these, and you build a multiplatform
> > >> > kernel which includes PL310 support, you don't wait for any of
> > >> > these and you probably see a lot of data corruption as a result.
> > >> 
> > >> Oops. I guess there are not many users as the L220 was primarily used
> > >> with the 1176 (and 11MP?) IIRC. I guess one of the primary 1176 based
> > >> platforms currently used is RPi, but it appears the BCM2835 doesn't
> > >> have an L2 (other than some custom L2 for the GPU).
> > > 
> > > Won't Freescale i.MX35 help here ? It's 1136JF-S core and has some L2
> > > cache.
> > 
> > No. 1136 uses L210. 1176 uses L220. There was the i.MX37 which had an
> > 1176, but it was pretty short lived and never saw upstream support.
> 
> Don't worry too much about the L220 - the Realview boards have one, and
> I have one Realview EB board:

OK, gotcha.

Best regards,
Marek Vasut