Re: [PATCH v2] twl4030 reboot workaround

[Mike Turquette <mturquette@ti.com>]

Gopinath, Thara wrote:
> 
>>> -----Original Message-----
>>> From: linux-omap-owner@vger.kernel.org [mailto:linux-omap-owner@vger.kernel.org] On Behalf Of Mike
>>> Rapoport
>>> Sent: Friday, July 30, 2010 12:41 AM
>>> To: Mikko Rapeli
>>> Cc: linux-omap@vger.kernel.org; Turquette, Mike; sameo@linux.intel.com
>>> Subject: Re: [PATCH v2] twl4030 reboot workaround
>>>
>>> Hi
>>>
>>> On Thu, Jul 29, 2010 at 9:41 AM, Mikko Rapeli
>>> <ext-mikko.rapeli@nokia.com> 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."
>>> I had a similar issue when my system hanged on hard reset when there
>>> was a TWL sleep script installed.
>>> The workaround I've found was to install the sleep script immediately
>>> before entering the suspend state and remove the script on the resume
>>> path.
>>> If you think that such approach is appropriate I can send a patch.
> 
> How do you hit the off state(Vdd's at 0 V) in the idle path then? Or do you do this every
> time in the idle thread also?

I do not think it is appropriate to add/remove the sleep script 
before/after every OFF mode case.  The script should be programmed once 
and left alone EXCEPT in the case of warm reset.

If there are other corner cases where SYS_OFFMODE goes low, then we 
should cover those with similar fixes to the warm reset fix, but in 
general I think the policy should be to leave the scripts alone once 
programmed

Dynamically programming/removing the scripts around OFF transitions 
increases software overhead for those transitions even more which is 
very undesirable.

Mike

> Regards
> Thara