linux-kernel - Re: [PATCH v2 1/4] ARM: pwm: sun4i: unification of register operations for support sun6i.

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Date:   Fri, 10 Feb 2017 09:38:04 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Волков Сергей 
        <lis8215@...il.com>
Cc:     linux-sunxi@...glegroups.com,
        Thierry Reding <thierry.reding@...il.com>, robh+dt@...nel.org,
        mark.rutland@....com, Chen-Yu Tsai <wens@...e.org>,
        linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] ARM: pwm: sun4i: unification of register
 operations for support sun6i.

Hi,

On Wed, Feb 08, 2017 at 07:41:55PM +0300, Волков Сергей wrote:
> Hello all,
> 
> >> This patch not introduce new features, just prepare code for
> >> adding sun6i PWM driver in next commits.
> >>
> >> A31 SoC have a different map of PWM registers than others ASoCs,
> >> but register bits purposes are very similar.
> >>
> >> This patch introduce set of register access routines, which
> >> are common for existing in driver ASoCs:
> >>  - ctl_rdy   - checks the ready bit of specified PWM channel,
> >>  - ctl_read  - reads value from control register of specified PWM
> channel,
> >>  - ctl_write - writes significant bits to control register of specified
> PWM channel,
> >>  - prd_read  - reads value from period register of specified PWM channel,
> >>  - prd_write - writes value to period register of specified PWM channel.
> >> Driver code redesigned to use the new routines.
> >
> > Why don't you use regmap for that?
> 
> First of all, i'm newbie and its my first patchset. I just remake
> what i see in the driver. I even don't suspect about use regmap
> here.

Don't worry, a review is here to point where things could be better,
which doesn't mean that you did wrong :)

> Second thing - i can't test these driver on all existing sunxi SoCs,
> i have only A31 and A20 based boards where only pwm0 is
> accessible. Huge redesign cause bigger chance to make a mistake.

Don't worry about that either. We have a good number of platforms
using the PWMs already. If there's something broken at some point,
we'll catch it as well.

> If you think regmap solution is a must, then i will do that. This
> will be a good experience for me.

Yes, this really should cover what you're trying to do here,
especially reg_field.

You can have a look at drivers/reset/sti/reset-syscfg.c if you want to
have a look at a rather simple driver using it.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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