Re: [PATCH] twl4030 reboot workaround

[Mikko Rapeli <ext-mikko.rapeli@nokia.com>]

On Wed, Jul 28, 2010 at 12:18:11PM +0200, De-Schrijver Peter
(Nokia-MS/Helsinki) wrote:
> On Wed, Jul 28, 2010 at 11:41:32AM +0200, Rapeli Mikko (EXT-Ixonos/Oulu)
> wrote:
> > From: Mikko Rapeli <ext-mikko.rapeli@nokia.com>
> > 
> > Original patch: http://marc.info/?l=linux-omap&m=126522625032441&w=2
> > 
> > "Removes TWL4030 sleep script prior to rebooting, only on OMAP3. This is
> > necessary since DPLL3 reset causes SYS_OFFMODE pin to go low, resulting
> > in the sleep script being executed on TWL4030. This usually results in
> > VDD1 & VDD2 voltage collapse while ROM code is executing, followed by an
> > MPU Watch Dog reset or worse, an irrecoverable hang."
> > 
> > Original patch resulted in a crash due to sleeping i2c calls late in the
> > reboot sequence. Here's how to trigger the crash:
> > 
> > 	# cat /dev/urandom > /foo &
> > 	sync();
> >         reboot(LINUX_REBOOT_CMD_RESTART2);
> > 
> > Kernel trace from 2.6.32:
> > 
> > Unable to handle kernel NULL pointer dereference at virtual address 00000000
> > pgd = c0004000
> > [00000000] *pgd=00000000
> > Internal error: Oops: 805 [#2] PREEMPT
> > ...
> > [<c00b3210>] (exit_mmap+0x1d4/0x1f8) from [<c006069c>] (mmput+0x34/0x110)
> > [<c006069c>] (mmput+0x34/0x110) from [<c0064a90>] (exit_mm+0x140/0x180)
> > [<c0064a90>] (exit_mm+0x140/0x180) from [<c00668ec>] (do_exit+0x5d8/0x6ac)
> > [<c00668ec>] (do_exit+0x5d8/0x6ac) from [<c0035858>] (die+0x2d4/0x2e0)
> > [<c0035858>] (die+0x2d4/0x2e0) from [<c0035904>] (baddataabort+0x0/0x50)
> > [<c0035904>] (baddataabort+0x0/0x50) from [<c0274ff4>] (i2c_transfer+0xec/0x104)
> > [<c0274ff4>] (i2c_transfer+0xec/0x104) from [<00000001>] (0x1)
> > 
> > Fix is to move reboot preparations into a reboot notifier.
> > 
> 
> And what if we get an OMAP3 watchdog reset ? In this case there is no
> software to remove the script...

Well, I don't know. We have seen boot and reboot failures and this
remove script patch set has helped to reduce those failures.

-Mikko