linux-kernel - Re: [PATCH V4 2/2] regulator: mt6323: Add support for MT6323 regulator

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Message-ID: <1454553763.24913.8.camel@mtksdaap41>
Date:	Thu, 4 Feb 2016 10:42:43 +0800
From:	menghui lin <menghui.lin@...iatek.com>
To:	Mark Brown <broonie@...nel.org>
CC:	<linux-kernel@...r.kernel.org>,
	HenryC Chen (陳建豪) 
	<HenryC.Chen@...iatek.com>, Liam Girdwood <lgirdwood@...il.com>,
	<linux-mediatek@...ts.infradead.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Chen Zhong <chen.zhong@...iatek.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	"John Crispin" <blogic@...nwrt.org>
Subject: Re: [PATCH V4 2/2] regulator: mt6323: Add support for MT6323
 regulator

On Wed, 2016-02-03 at 12:29 +0000, Mark Brown wrote:
> On Wed, Feb 03, 2016 at 01:39:02PM +0800, menghui lin wrote:
> > On Tue, 2016-02-02 at 19:38 +0000, Mark Brown wrote:
> 
> > > How does the driver know if it needs to change the mode (ie, how can it
> > > tell if the current mode is inadequate) and surely if we can only change
> > > in one direction this isn't terribly useful?
> 
> > I think the datasheet of buck/ldo could provide information about power
> > capability of each mode. The driver should adjust regulator mode per its
> > device's power requirement.
> 
> That's of no help for a consumer driver which doesn't know what
> regulator is supplying it.
> 
> > case 1:
> 
> > We have a USB typeC micro-controller, which has two modes - standby and
> > normal. It requires 1.8V and 3.3V to operate (both powers are always
> > on). The device stays in standby mode when there is no cable in. When
> > cable in, we got an interrupt and change device into normal mode.
> 
> > The standby mode power consumption is quite small, so we would like the
> > change mode of regulator into STANDBY to save more power. And we change
> > into NORMAL when we receive cable-in interrupt.
> 
> This seems like something that we ought to be doing via runtime PM
> anyway which should be going through the suspend mode bindings, though
> that would need some plumbing in.
> 
> > case 2:
> 
> > About buck regulator for CPU, it usually provides PWM mode, PWM/PFM Auto
> > mode, PFM mode. I think it could map to FAST, NORMAL, IDLE mode
> > respectively. Most of time we would use just normal mode. However, we
> > would change regulator into PWM mode time to time to test buck output
> > performance on the tested board.
> 
> That's a test use that doesn't seem a good fit for upstream at all.

Hi Mark,

Thanks for your response.
It seems more work is required for dynamic mode switch.
For MT6323 regulator patch, we would remove mode-switch related code for
now to provide basic regulator support first.