linux-kernel - Re: [PATCH] mfd: twl4030-power: Fix poweroff with PM configuration enabled

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Date:	Wed, 12 Nov 2014 17:45:12 +0200
From:	Grazvydas Ignotas <notasas@...il.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Igor Grinberg <grinberg@...pulab.co.il>,
	Lee Jones <lee.jones@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"Dr. H. Nikolaus Schaller" <hns@...delico.com>
Subject: Re: [PATCH] mfd: twl4030-power: Fix poweroff with PM configuration enabled

On Tue, Nov 4, 2014 at 5:42 PM, Tony Lindgren <tony@...mide.com> wrote:
> * Igor Grinberg <grinberg@...pulab.co.il> [141104 05:22]:
>> Hi Tony,
>>
>> On 11/02/14 20:07, Tony Lindgren wrote:
>> > Commit e7cd1d1eb16f ("mfd: twl4030-power: Add generic reset
>> > configuration") enabled configuring the PM features for twl4030.
>> >
>> > This caused poweroff command to fail on devices that have the
>> > BCI charger on twl4030 wired, or have power wired for VBUS.
>> > Instead of powering off, the device reboots. This is because
>> > voltage is detected on charger or VBUS with the default bits
>> > enabled for the power transition registers.
>> >
>> > To fix the issue, let's just clear VBUS and CHG bits as we want
>> > poweroff command to keep the system powered off.
>>
>> What about devices that really need to start once VBUS or CHG is connected?
>
> More handling can be added for some cases. With this patch the
> poweron bits will clear to defaults if power is completely removed.
> So start-up with VBUS and CHG works in that case.
>
> However, if you have a battery connected, and you poweroff, with
> this patch the device won't power up with VBUS or CHG connected.
>
> Note that most battery operated devices are not using the charger
> on twl4030 because it has issues charging a completely empty
> battery AFAIK. So most battery powered devices have been using an
> external USB charger chip that's not affected by this patch.

Pandora does, as well as GTA04 AFAIK, but that's not "most devices" I
guess.. At least pandora was booting up on charger connect up until
now. I don't know why shutdown used to work for Russell in legacy boot
and it changed for DT, the device would always start up when there was
AC power here.


Grazvydas

>
> We could consider exporting a function for the charger driver to
> configure the poweron mask. And we could also consider passing a
> mask in ti,use_poweroff = 0xff.
>
>> It seems to me that forcing these bits on power off can break that kind of
>> devices and these settings should really be board specific.
>> What do you think?
>
> There's a patch series for "[RFC,01/16] kernel: Add support for
> poweroff handler call chain" that should help with that. For sure
> the poweroff handling needs to be board specific as some systems
> may need to use a GPIO to shut off a regulator powering something
> before powering off the SoC.
>
> Regards,
>
> Tony
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