linux-kernel - Re: [PATCH v2 07/10] regulator: Add driver for Maxim 77802 PMIC regulators

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Date:	Tue, 17 Jun 2014 18:05:29 +0200
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Mark Brown <broonie@...nel.org>
CC:	Lee Jones <lee.jones@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Mike Turquette <mturquette@...aro.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Doug Anderson <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Sjoerd Simons <sjoerd.simons@...labora.co.uk>,
	Daniel Stone <daniels@...labora.com>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/10] regulator: Add driver for Maxim 77802 PMIC regulators

Hello Mark,

On 06/17/2014 04:12 PM, Mark Brown wrote:
> On Tue, Jun 17, 2014 at 12:49:56PM +0200, Javier Martinez Canillas wrote:
>> On 06/16/2014 09:25 PM, Mark Brown wrote:
> 
>> >> +	config.dev = &pdev->dev;
> 
>> > Are you sure this shouldn't be the MFD?
> 
>> I just looked at regulator_register() and saw that it does rdev->dev.parent =
>> dev, so yes this has to be the MFD.
>

I noticed that many drivers set config.dev = &pdev->dev. The original Chrome OS
max77xxx driver and max77686 are two examples but others drivers do the same:

$ git grep "config.dev = &pdev->dev" drivers/regulator/ | wc -l
35
$ git grep "config.dev = pdev->dev.parent" drivers/regulator/ | wc -l
11

And also I see that mfd_add_device() calls
devm_regulator_bulk_register_supply_alias(&pdev->dev,...) so I'm confused now
about what the correct device should be...

> Do the regulators manage to get their supplies?
> 

There are no current support in mainline for the devices that use the regulators
in this PMIC so I can't tell you if consumers manage to get their supplies
correctly (e.g: if regulator_dev_lookup succeeds).

But I see in the kernel log that the regulators are registered and configured as
expected [0] and also the driver in the Chrome OS 3.8 kernel is working for sure
and sets config.dev to &pdev->dev instead of the MFD.

>> So, for now I thought it made sense to set the operating mode to normal on
>> probe() but I'll change it to read from the hardware if that is better.
> 
> Yes, otherwise if the device is configured otherwise then when we change
> the configuration we may break something.
> 
>> I guess I should check in the datasheet if a sane default operating mode for
>> LDOs is expected when the chip is reseted or if this is left undefined and also
>> if the bootloader already set this.
> 
> You can't do anything based on the particular bootloader you're using in
> your current system, this has to work in other systems.
> 

Yes, that's why I thought it was a good idea to set to a default operational
mode but I'll change it to read from the hardware instead.

Thanks a lot and best regards,
Javier

[0]: http://pastebin.com/raw.php?i=8yyMXcGD
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