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

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Message-ID: <54591265.3030207@compulab.co.il>
Date:	Tue, 04 Nov 2014 19:52:37 +0200
From:	Igor Grinberg <grinberg@...pulab.co.il>
To:	Tony Lindgren <tony@...mide.com>
CC:	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-omap@...r.kernel.org
Subject: Re: [PATCH] mfd: twl4030-power: Fix poweroff with PM configuration
 enabled

On 11/04/14 17:42, Tony Lindgren 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.
> 
> 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.

Ok. That sounds better to me.
Yet, if you say there are no such devices in practice,
IMHO, we can merge this.

> 
>> 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.

Yes, I've seen this series.
I'm not sure though that I understand how is this supposed
to be used with DT...
Through the regulator bindings?
Which will tell it to hook up on the call chain?


-- 
Regards,
Igor.
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