[PATCH RFT 2/2] arm: dts: disable CCI on exynos420 based arndale-octa

[k.kozlowski@samsung.com (Krzysztof Kozlowski)]

On pon, 2014-12-01 at 11:09 +0000, Russell King - ARM Linux wrote:
> On Mon, Dec 01, 2014 at 10:03:28AM +0100, Krzysztof Kozlowski wrote:
> > On pi?, 2014-11-28 at 21:09 +0530, Abhilash Kesavan wrote:
> > > Hello Krzysztof,
> > > 
> > > On Fri, Nov 28, 2014 at 8:49 PM, Krzysztof Kozlowski
> > > <k.kozlowski@samsung.com> wrote:
> > > > On pi?, 2014-11-28 at 20:20 +0530, Abhilash Kesavan wrote:
> > > >> The arndale-octa board was giving "imprecise external aborts" during
> > > >> boot-up with MCPM enabled. CCI enablement of the boot cluster was found
> > > >> to be the cause of these aborts (possibly because the secure f/w was not
> > > >> allowing it). Hence, disable CCI for the arndale-octa board.
> > > >>
> > > >> Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
> > > >> ---
> > > >>  arch/arm/boot/dts/exynos5420-arndale-octa.dts |    4 ++++
> > > >>  arch/arm/boot/dts/exynos5420.dtsi             |    2 +-
> > > >>  2 files changed, 5 insertions(+), 1 deletion(-)
> > > >
> > > > I tested these 2 patches on Arndale Octa but there are no improvements.
> > > > I still got imprecise aborts (some not fatal and sometimes killing init
> > > > with full backtrace).
> > > 
> > > Thanks for testing. Are you testing this with exynos_defconfig with no
> > > other changes ? Can you please confirm from the bootlog that MCPM and
> > > CCI are not being initialized.
> > > 
> > That was exynos_defconfig with disabled DRM and enabled some debug,
> > next-20141128.
> > 
> > When I tried only exynos_defconfig (with disabled DRM) it worked fine...
> > So the imprecise aborts were caused by one of following debug options:
> > 
> > DEBUG_SECTION_MISMATCH
> > DYNAMIC_DEBUG
> > DEBUG_ATOMIC_SLEEP
> > DEBUG_PREEMPT
> > PROVE_LOCKING
> > LOCKUP_DETECTOR
> > DEBUG_LOCK_ALLOC
> > PROVE_RCU
> > DEBUG_RT_MUTEXES
> > DEBUG_MUTEXES
> > DEBUG_SPINLOCK
> > DEBUG_LIST
> > DEBUG_PAGEALLOC
> > SPARSE_RCU_POINTER
> > DEBUG_FS
> > PM_DEBUG
> > PM_ADVANCED_DEBUG
> > GPIO_SYSFS
> > 
> > > Can you remove these 2 patches and on linux-next check if you are
> > > getting aborts even with 5420_MCPM disabled.
> > 
> > I tried this already and imprecise aborts shown, however with my
> > debugging options above.
> > 
> > Overall the patches seems to work properly (although the debugging issue
> > needs to be resolved still), so:
> > 
> > On Arndale Octa (Exynos 5420):
> > Tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> 
> Reading this message, it seems that this should *not* be given a tested-by,
> because it seems from what you've reported above, they don't work correctly.
> 
> If you have to turn debugging options off in order to get the kernel to
> apparently run correctly after applying some patches, it means those
> patches themselves are probably buggy, rather than the debug itself
> being buggy.
> 
> I'd suggest that you have some further work to do (a manual bisect of the
> config options you've disabled) to discover which is the cause of the
> problem.
> 
> It could be that the code introduces something like a use-after-free bug.

Maybe I was to eager to add Tested-by but (without debugging options)
one imprecise-abort disappears with the patchset. Other issues seem not
to be fixed.

Best regards,
Krzysztof