[PATCH] omap: wd_timer: Fix crash frm wdt_probe when !CONFIG_RUNTIME_PM

-----Original Message-----
From: Paul Walmsley [mailto:paul at pwsan.com]
Sent: Thursday, January 06, 2011 11:56 PM
To: Santosh Shilimkar
Cc: linux-omap at vger.kernel.org; linux-arm-kernel at lists.infradead.org
Subject: Re: [PATCH] omap: wd_timer: Fix crash frm wdt_probe when
!CONFIG_RUNTIME_PM

Hi Santosh,

On Wed, 5 Jan 2011, Santosh Shilimkar wrote:

quoted

Commit ff2516fb 'wd_timer: disable on boot via hwmod postsetup

mechanism'

quoted

introduced watchdog timer state state management using

postsetup_state.

quoted

This was done to allow some board files to support watchdog

coverage

quoted

throughout kernel initialization and it work as intended when

RUNTIME_PM

quoted

is enabled.

With !CONFIG_RUNTIME_PM and no board is specifically requests

watchdog

quoted

to remain enabled the omap_wdt_probe crashesh. This is because

hwmod

quoted

in absense of runtime PM unable to turn watchdog clocks because

it's

quoted

state is set to be disabled. For rest of the device, the state is
set as enabled in absense of RUNTIME_PM

[    1.372558] Unhandled fault: imprecise external abort (0x1406)

at 0xad733eeb

quoted

[    1.379913] Internal error: : 1406 [#1] SMP
[    1.384277] last sysfs file:
[    1.387359] Modules linked in:
[    1.390563] CPU: 0    Tainted: G        W    (2.6.37-rc7-00265-

g4298a4c-dirty #23)

quoted

[    1.398468] PC is at omap_wdt_disable+0x2c/0x3c
[    1.403198] LR is at omap_wdt_probe+0x124/0x1e0
[    1.407928] pc : [<c02f5bf4>]    lr : [<c03be10c>]    psr:

60000013

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[    1.407958] sp : df833f00  ip : 00000000  fp : 00000000
[    1.419921] r10: c0ac57ac  r9 : df959e00  r8 : 00000000
[    1.425384] r7 : df959e08  r6 : df8000c0  r5 : df95bebc  r4 :

df87dde0

quoted

[    1.432189] r3 : fc314000  r2 : 00005555  r1 : fc314034  r0 :

df87dde0

quoted

This patch make the default watchdog state to be enabled in case

of

quoted

!CONFIG_RUNTIME_PM. This fixes the crash

Signed-off-by: Santosh Shilimkar <redacted>
Cc: Paul Walmsley <paul@pwsan.com>
---
Paul, I am not too sure if it breaks your _shutdown idea of

watchdog

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timer.

Maybe.  What happens in a case where the bootloader enables the
watchdog,
but the booting kernel is compiled with !CONFIG_OMAP_WATCHDOG and
!CONFIG_PM_RUNTIME?  Won't the watchdog reset the MPU unexpectedly
in that
case?  Or am I missing something...

I had a same doubght. But the test I did with and without
"CONFIG_OMAP_WATCHDOG" just at kernel level. The TI bootloader
have MPU watchdog being always disabled.

Will do a test on this scenario by explicitly disabling the
MPU WDT in bootloader.

Regards,
Santosh