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

[santosh.shilimkar@ti.com (Santosh Shilimkar)]

> -----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:
>
> > Commit ff2516fb 'wd_timer: disable on boot via hwmod postsetup
> mechanism'
> > introduced watchdog timer state state management using
> postsetup_state.
> > This was done to allow some board files to support watchdog
> coverage
> > throughout kernel initialization and it work as intended when
> RUNTIME_PM
> > is enabled.
> >
> > With !CONFIG_RUNTIME_PM and no board is specifically requests
> watchdog
> > to remain enabled the omap_wdt_probe crashesh. This is because
> hwmod
> > in absense of runtime PM unable to turn watchdog clocks because
> it's
> > 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
> > [    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)
> > [    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
> > [    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
> > [    1.432189] r3 : fc314000  r2 : 00005555  r1 : fc314034  r0 :
> df87dde0
> >
> > This patch make the default watchdog state to be enabled in case
> of
> > !CONFIG_RUNTIME_PM. This fixes the crash
> >
> > Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
> > Cc: Paul Walmsley <paul@pwsan.com>
> > ---
> > Paul, I am not too sure if it breaks your _shutdown idea of
> watchdog
> > 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