linux-kernel - Re: [PATCH 2/3] regulator: s2mps11: Merge S2MPA01 driver

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Message-id: <1401177400.8073.16.camel@AMDC1943>
Date:	Tue, 27 May 2014 09:56:40 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Yadwinder Singh Brar <yadi.brar01@...il.com>
Cc:	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Sangbeom Kim <sbkim73@...sung.com>,
	Lee Jones <lee.jones@...aro.org>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/3] regulator: s2mps11: Merge S2MPA01 driver

On wto, 2014-05-27 at 12:00 +0530, Yadwinder Singh Brar wrote:
> On Mon, May 26, 2014 at 6:50 PM, Krzysztof Kozlowski
> <k.kozlowski@...sung.com> wrote:
> > Add S2MPA01 support to the s2mps11 regulator driver. This obsoletes the
> > s2mpa01 regulator driver.
> >
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> 
> > @@ -216,30 +250,20 @@ static int s2mps11_set_ramp_delay(struct regulator_dev *rdev, int ramp_delay)
> >                         ramp_delay = s2mps11->ramp_delay16;
> >                 break;
> >         case S2MPX_BUCK2:
> > -               if (!ramp_delay) {
> > -                       ramp_enable = 0;
> > -                       break;
> > -               }
> > -
> 
> What if we want to disable ramp_delay from DT ?

It will work OK because at the beginning of s2mps11_set_ramp_delay():
	unsigned int ramp_disable = !ramp_delay;
This 'ramp_disable' is later used if enable/disable is supported.
> 
> > -               s2mps11->ramp_delay2 = ramp_delay;
> > +               if (s2mps11->dev_type == S2MPS11X ||
> > +                               ramp_delay > s2mps11->ramp_delay2)
> > +                       s2mps11->ramp_delay2 = ramp_delay;
> > +               else /* S2MPA01 && ramp_delay <= s2mpa01->ramp_delay24 */
> > +                       ramp_delay = s2mps11->ramp_delay2;
> 
> Here ramp_delay = 0(ramp_disable case) is also getting over written,
> if required to take care of it later.

The same, it is already stored as 'ramp_disable' local variable.

> 
> >                 break;
> >         case S2MPX_BUCK3:
> > -               if (!ramp_delay) {
> > -                       ramp_enable = 0;
> > -                       break;
> > -               }
> 
> [snip]
> 
> >
> > -       if (!ramp_enable)
> > -               goto ramp_disable;
> > -
> > -       /* Ramp delay can be enabled/disabled only for buck[2346] */
> >         if (ramp_reg->enable_supported) {
> > +               if (ramp_disable)
> 
> typo ?    if (!ramp_enable) / if (!ramp_delay) ?

I think it is good. I changed the 'ramp_enable' into 'ramp_disable'.

Anyway while reviewing the code I found that I didn't updated the case
statements with new BUCKX enum values and the register for
enable/disable is hard-coded. I'll fix it.
> 
> > +                       goto ramp_disable;
> > +
> 
> 
> Also TBH, I can't get rationale behind this merge, As i can't see
> considerable reduction in no of C code lines in comp of added
> complexity.
>  Is there considerable advantage in binary stats of single driver as
> compare to independent drivers?

Overall more code is removed than added:
6 files changed, 454 insertions(+), 719 deletions(-)
but you are right that the code for ramp delay is now more complex. What
is worth noting now most of ramp delay settings are moved to an array:

static const struct s2mpx_ramp_reg s2mps11_ramp_regs[] = {
	[S2MPX_BUCK1]   = s2mps11_ramp_reg(BUCK16),
	[S2MPX_BUCK2]   = s2mps11_buck2346_ramp_reg(BUCK2, RAMP, BUCK2),
	[S2MPX_BUCK3]   = s2mps11_buck2346_ramp_reg(BUCK34, RAMP, BUCK3)

instead of being hard-coded into the big switch statement like it was
before.

Alternative solution to complex ramp delay setting is to just use
original functions: s2mps11_set_ramp_delay and s2mpa01_set_ramp_delay.

These chips are really similar so having two drivers seems like doubling
the effort for maintaining them.

Thanks for comments.

Best regards,
Krzysztof

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