[PATCH v4] ARM: Add check for Cortex-A15 errata 798181 ECO

[Russell King - ARM Linux]

On Tue, Sep 03, 2013 at 10:13:47AM +0100, Will Deacon wrote:
> On Mon, Sep 02, 2013 at 10:31:25PM +0100, Russell King - ARM Linux wrote:
> > On Mon, Sep 02, 2013 at 02:58:42PM +0100, Russell King - ARM Linux wrote:
> > > On Sun, Aug 25, 2013 at 09:25:47AM -0500, Rob Herring wrote:
> > > > From: Rob Herring <rob.herring at calxeda.com>
> > > > 
> > > > The work-around for A15 errata 798181 is not needed if appropriate ECO
> > > > fixes have been applied to r3p2 and earlier core revisions. This can be
> > > > checked by reading REVIDR register bits 4 and 9. If only bit 4 is set,
> > > > then the IPI broadcast can be skipped.
> > > > 
> > > > Signed-off-by: Rob Herring <rob.herring at calxeda.com>
> > > 
> > > So, this patch in the patch system claims to be against v3.11-rc2:
> > > 
> > > $ git checkout v3.11-rc2
> > > ...
> > > $ pdb gitapply 7804/2
> > > Patching 7804/2...
> > > git apply --whitespace=fix -p1 --index --check > /tmp/pdb.15757 2>&1 exited with non-zero status: 256
> > > error: patch failed: arch/arm/include/asm/tlbflush.h:443
> > > error: arch/arm/include/asm/tlbflush.h: patch does not apply
> > > error: patch failed: arch/arm/kernel/smp_tlb.c:70
> > > error: arch/arm/kernel/smp_tlb.c: patch does not apply
> > > error: patch failed: arch/arm/mm/context.c:245
> > > error: arch/arm/mm/context.c: patch does not apply
> > > 
> > > > v3:
> > > > - Rebase to v3.11-rc5 due to commit 1f49856 (ARM: 7789/1: Do not run
> > > >  dummy_flush_tlb_a15_erratum() on non-Cortex-A15)
> > > > - Move the revision checking out of line and use function ptrs.
> > > 
> > > Hmm, so -rc5 not -rc2 that you put into the patch system...  Also, the
> > > patch you put into the patch system didn't have Will's ack on it.
> > 
> > And... merging everything together tonight gives me a conflict with Will's
> > barriers patches, which I've resolved like this - this will need to be
> > checked:
> 
> Thanks Russell; looks ok from my side.

It turns out that it's not quite okay - sfr reported failures this morning
which are reflected in the nightly build, so I think I'm going to drop
Rob's patch.  It looks like the case where the workaround is disabled
hasn't been tested, which means almost everything fails with:

arch/arm/kernel/built-in.o: In function `setup_processor':
io.c:(.init.text+0x72c): undefined reference to `erratum_a15_798181_init'