[RFC] Fix omap3 booting with thumb2 compiled kernel

Tony Lindgren [off-list ref] writes:

* Kevin Hilman [off-list ref] [150527 15:20]:

quoted

[ fix email for Dave Martin, +Tyler ]

Tony Lindgren [off-list ref] writes:

quoted

The power management related assembly needs to interact with
ARM mode bootrom code, so we need to keep most of the related
assembly in ARM mode.

Currently we are entering into and ARM mode assembly function
from thumb2 mode, so we need to make sure we switch to ARM
mode. And we need to do that again after the cache flush.

---

Kevin told me about this earlier today.. 

And for full boot log/panics, see the kernelci.org thumb2 kernel boots
that fail: http://kernelci.org/boot/?THUMB2_KERNEL&fail

quoted

Anybody got better ideas for a fix here?

FWIW, a quick test of this patch makes my omap3-beagle-xm pass a simple
boot test, but it fails with off idle.

Thanks to Stephen Boyd's suggestion of checking the missing ENDPROC,
here's a better fix :) Now off idle works too.

Regards,

Tony

8 <----------------------
From: Tony Lindgren <tony@atomide.com>
Date: Wed, 27 May 2015 15:33:57 -0700
Subject: [PATCH] ARM: OMAP3: Fix booting with thumb2 kernel

We get a NULL pointer dereference on omap3 for thumb2 compiled kernels:

Internal error: Oops: 80000005 [#1] SMP THUMB2
...
[<c046497b>] (_raw_spin_unlock_irqrestore) from [<c0024375>]
(omap3_enter_idle_bm+0xc5/0x178)
[<c0024375>] (omap3_enter_idle_bm) from [<c0374e63>]
(cpuidle_enter_state+0x77/0x27c)
[<c0374e63>] (cpuidle_enter_state) from [<c00627f1>]
(cpu_startup_entry+0x155/0x23c)
[<c00627f1>] (cpu_startup_entry) from [<c06b9a47>]
(start_kernel+0x32f/0x338)
[<c06b9a47>] (start_kernel) from [<8000807f>] (0x8000807f)

The power management related assembly on moaps needs to interact with
ARM mode bootrom code, so we need to keep most of the related assembly
in ARM mode.

Turns out this error is because of missing ENDPROC for assembly code
as suggested by Stephen Boyd [off-list ref]. Let's add the
missing ENDPROC in two places to sleep34xx.S, and also remove the
earlier mystery code that was probably also caused by missing ENDPROC
for earlier kernels.

Reported-by: Kevin Hilman <khilman@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Yup, boot test is now passing for me on omap3-beagle, omap3-beagle-xm,
omap3-n900, omap3-overo-tobi, omap3-overo-storm-tobi.

Tested-by: Kevin Hilman <redacted>

Thanks for the quick fix.

Next step is to look at the exynos4412-odroidu3 failure which probably
has a similar cause.

Kevin