linux-kernel - Re: [PATCH] regulator: ab8500: Fix get

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Message-ID: <516C1323.9060302@stericsson.com>
Date:	Mon, 15 Apr 2013 16:48:03 +0200
From:	Bengt Jönsson <bengt.g.jonsson@...ricsson.com>
To:	Axel Lin <axel.lin@...ics.com>
Cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Lee Jones <lee.jones@...aro.org>,
	Yvan FILLION <yvan.fillion@...ricsson.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] regulator: ab8500: Fix get_mode for shared mode regulators

On 04/15/2013 04:11 PM, Axel Lin wrote:
> 2013/4/15 Bengt Jönsson <bengt.g.jonsson@...ricsson.com>:
>> On 04/15/2013 02:13 PM, Axel Lin wrote:
>>>> I guess what you don't like with the current approach is that the driver
>>>> returns REGULATOR_MODE_IDLE in some cases where the mode register is set
>>>> to
>>>> LP. But I think, with patch applied, the control may be wrong in some
>>>> cases
>>>> because the regulator framework will call get_mode and see that the mode
>>>> is
>>>> already correct and not call set_mode so lp_mode_req will not get
>>>> updated. I
>>> I got your point now.
>>>
>>> My point is get_mode() should always return "correct" status by
>>> reading register value.
>>> And as you mentioned, regulator_set_mode() did check current mode and
>>> won't call
>>> set_mode callback if current mode is the same as the target mode.
>>> And that is why this patch won't work.
>>>
>>> However, Make get_mode() return "incorrect" status to avoid above
>>> issue looks wrong to me.
>>>
>>> Regards,
>>> Axel
>> I understand your point of view, but I think that the framework (as it is
>> currently implemented) expects to get the requested mode of the regulator in
>> this case, not the actual mode (in the shared mode register).The alternative
>> could be to change the framework in some way.
>>
>> Any ideas? Otherwise I propose to keep the code and maybe add a comment.
> It looks to me a simple fix is to just get rid of the check of old mode with
> new mode setting.
>
> Something like reverse of commit 500b4ac90d1103
> "regulator: return set_mode is same mode is requested" would work.
>
> Regards,
> Axel
Reverting 500b4ac90d1103 makes sense, but first I want to mention two 
things:
1. In some cases it is not even possible to know the actual current 
state of a regulator because it is controlled by HW as well as SW. We 
have several examples of this.
2. regulator_enable/disable also checks the current status before 
setting the regulator. Should these checks be removed as well?

Regards,

Bengt

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