linux-kernel - Re: [PATCH v5 05/46] pwm: introduce the pwm

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Date:	Tue, 12 Apr 2016 15:15:03 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	linux-pwm@...r.kernel.org,
	Mike Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>, linux-clk@...r.kernel.org,
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	Guenter Roeck <linux@...ck-us.net>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
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	Ryan Mallon <rmallon@...il.com>,
	Alexander Shiyan <shc_work@...l.ru>, Milo Kim <milo.kim@...com>
Subject: Re: [PATCH v5 05/46] pwm: introduce the pwm_args concept

On Tue, Apr 12, 2016 at 03:06:27PM +0200, Boris Brezillon wrote:
> On Tue, 12 Apr 2016 13:39:12 +0200
> Thierry Reding <thierry.reding@...il.com> wrote:
> 
> > On Wed, Mar 30, 2016 at 10:03:28PM +0200, Boris Brezillon wrote:
> > > Currently the PWM core mixes the current PWM state with the per-platform
> > > reference config (specified through the PWM lookup table, DT definition or
> > > directly hardcoded in PWM drivers).
> > > 
> > > Create a pwm_args struct to store this reference config, so that PWM users
> > > can differentiate the current config from the reference one.
> > > 
> > > Patch all places where pwm->args should be initialized. We keep the
> > > pwm_set_polarity/period() calls until all PWM users are patched to
> > > use pwm_args instead of pwm_get_period/polarity().
> > 
> > Perhaps a helper would be useful? Something like:
> > 
> > 	static inline void
> > 	pwm_apply_args(struct pwm_device *pwm, const struct pwm_args *args)
> > 	{
> > 		pwm_set_duty_cycle(pwm, args->duty_cycle);
> > 		pwm_set_period(pwm, args->period);
> > 	}
> > 
> > ? That would make it slightly easier to get rid of it again after all
> > clients have been converted.
> > 
> > With the exception of pwm-clps711x all of these args are set at of_xlate
> > time (for DT) or from the lookup table in pwm_get() (for non-DT), so it
> > might even be possible to move this call to the core, so that removal of
> > it will be a one-liner.
> 
> Okay, I think I misunderstood your suggestion. I thought you wanted
> this helper to set the reference config, but you actually want to apply
> a new state based on the PWM reference values.
> 
> Except that pwm_args does not contain all the required information to
> apply a full config (args->duty_cycle and args->enable do not exist).
> 
> This being said, in my v6 I moved the content of
> pwm_regulator_adjust_pwm_config() (patch 27) into a generic helper
> (pwm_adjust_config()). This helper is doing pretty much what you're
> suggesting here (but again, I'm not sure I correctly understood your
> suggestion :-/).

I'm not suggesting that pwm_apply_args() apply any state. I think we
both agreed earlier that the initial state (represented by pwm_args) was
never to be automatically applied.

What I was suggesting is that we move all the calls to pwm_set_period()
and pwm_set_duty_cycle() into a central location to make it easier to
remove them later in the series. This is really only temporary, so I
don't mind if we leave the calls sprinkled all over the place. At least
that way I hope we'll avoid confusion about what we're talking about =)

Thierry

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