[U-Boot] [PATCH 1/2 V2] arm926: Flush the data cache before disabling it.

[Sughosh Ganu]

On Mon Jan 16, 2012 at 10:57:05AM -0700, Tom Rini wrote:
> On Fri, Jan 13, 2012 at 10:38 AM, Sughosh Ganu <urwithsughosh at gmail.com> wrote:
> > hi Heiko,
> >
> > On Fri Jan 13, 2012 at 04:29:29PM +0100, Heiko Schocher wrote:
> >> Hello Sugosh,
> >>
> >> Sughosh Ganu wrote:
> >> > hi Christian,
> >> >
> >> > On Fri Jan 13, 2012 at 09:06:26AM +0100, Christian Riesch wrote:
> >> >> Hi Sughosh,
> >> >> I had a look at the patch and I tried to understand what's going on
> >> >> here (I must confess that I didn't know anything about this cache
> >> >> stuff).
> >> >
> >> >   Ok, thanks for taking time off to understand this issue.
> >> >
> >> >> On Tue, Jan 10, 2012 at 7:12 PM, Sughosh Ganu <urwithsughosh at gmail.com> wrote:
> >> >>> The current implementation invalidates the cache instead of flushing
> >> >>> it. This causes problems on platforms where the spl/u-boot is already
> >> >>> loaded to the RAM, with caches enabled by a first stage bootloader.
> >>
> >> Hmm.. how did u-boot work on such boards? How can u-boot work with D-Cache
> >> enabled, if u-boot is not initializing it? (And I think, on davinci SoC
> >> we have a none working uboot ethernet driver if d-cache is enabled too).
> >> There must be a page_table in DRAM for using D-Cache in U-Boot, if u-boot
> >> don't initialize it, it maybe overrides it ... or miss I something?
> >
> >  Well, there is some data in the cache, which if not flushed creates
> >  problems on my board. I get the board to boot just by commenting out
> >  cpu_init_crit call. My hypothesis that the D-cache is enabled is
> >  simply because cache invalidation followed by cache disabling breaks
> >  the board, while flushing it prior to disabling gets it to boot
> >  fine. This(invalidation) would not have been a problem if the cache
> >  was in the disabled state.
> 
> Putting my TI hat on, I've confirmed with the RBL folks that they
> aren't turning on ICACHE/DCACHE.

  Well, i'm not sure then why does the cache invalidation cause a
  problem on my platform. Btw, will this patch be
  accepted. Irrespective of the cache state on my board, it is not a
  wrong fix, and moreover results in the booting of my board.

  I haven't yet tried out reading the cache bit state in the spl. Will
  try out this experiment in a day or two, and share the results.

-sughosh