Re: Boot hang on Origen with (!SMP && CPU_IDLE)

[Arnd Bergmann <arnd@arndb.de>]

On Friday 03 January 2014, Tushar Behera wrote:
> Hi,
> 
> We are getting boot-time system hang on Exynos4210-based Origen board
> if the kernel (right now testing v3.13-rc6) is built using
> exynos_defconfig, disabling SMP support and enabling CPU_IDLE support.
> The boot log can be found here[1].
> 
> Git bisect points to following commit.
> 
> commit 87107d89052bcec1fe91b309631de4ed294a5171
> Author: Arnd Bergmann <arnd@arndb.de>
> Date:   Wed Jun 19 01:36:52 2013 +0900
> 
>     ARM: EXYNOS: Remove legacy L2X0 initialization
> 
>     Since Exynos is now supporting only DT-based boot, the old L2X0
>     initialization code is not needed anymore, so exynos4_l2x0_cache_init()
>     can be greatly simplified.
> 
>     Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>     Signed-off-by: Tomasz Figa <t.figa@samsung.com>
>     Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>     Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
> 
> Reverting the changes, the kernel boots up.
> 
> Any idea what else we might be missing?
> 
> [1] http://pastebin.com/0mP6ML4y

Hmm, the boot log contains no message about the l2 cache controller getting
initialized, which means that l2x0_of_init probably failed before calling
l2x0_init. It also seems that the dts files distributed with the kernel
are lacking nodes for the l2x0 device, which is indeed a perfectly good
explanation although it doesn't explain at all why it ever worked on
any system with my patch.

Can you check if there is a correct cache controller node in your device
tree, and whether it works when you add one? If so, we should probably
add a couple of stable backport patches to the dts files. It would also
be a good time to get rid of the L2_AUX_VAL and L2_AUX_MASK defines and
just read the respective settings from DT.

	Arnd