linux-kernel - Re: [PATCH v5 36/46] input: misc: max77693: switch to the atomic API

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Date:	Mon, 4 Apr 2016 17:34:33 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-pwm@...r.kernel.org,
	Mike Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>, linux-clk@...r.kernel.org,
	Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Kamil Debski <k.debski@...sung.com>, lm-sensors@...sensors.org,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	linux-input@...r.kernel.org, Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
	linux-leds@...r.kernel.org,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Chen-Yu Tsai <wens@...e.org>, linux-sunxi@...glegroups.com,
	Joachim Eastwood <manabian@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Heiko Stuebner <heiko@...ech.de>,
	linux-rockchip@...ts.infradead.org,
	Jingoo Han <jingoohan1@...il.com>,
	Lee Jones <lee.jones@...aro.org>, linux-fbdev@...r.kernel.org,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	linux-samsung-soc@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
	David Airlie <airlied@...ux.ie>,
	Daniel Vetter <daniel@...ll.ch>,
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	Hartley Sweeten <hsweeten@...ionengravers.com>,
	Ryan Mallon <rmallon@...il.com>,
	Alexander Shiyan <shc_work@...l.ru>, Milo Kim <milo.kim@...com>
Subject: Re: [PATCH v5 36/46] input: misc: max77693: switch to the atomic API

On Thu, Mar 31, 2016 at 08:57:18PM +0200, Boris Brezillon wrote:
> On Thu, 31 Mar 2016 10:48:01 -0700
> Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> 
> > Hi Boris,
> > 
> > On Wed, Mar 30, 2016 at 10:03:59PM +0200, Boris Brezillon wrote:
> > > pwm_config/enable/disable() have been deprecated and should be replaced
> > > by pwm_apply_state().
> > > 
> > > Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> > > ---
> > >  drivers/input/misc/max77693-haptic.c | 23 +++++++++++++++++------
> > >  1 file changed, 17 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/drivers/input/misc/max77693-haptic.c b/drivers/input/misc/max77693-haptic.c
> > > index cf6aac0..aef7dc4 100644
> > > --- a/drivers/input/misc/max77693-haptic.c
> > > +++ b/drivers/input/misc/max77693-haptic.c
> > > @@ -70,13 +70,16 @@ struct max77693_haptic {
> > >  
> > >  static int max77693_haptic_set_duty_cycle(struct max77693_haptic *haptic)
> > >  {
> > > +	struct pwm_state pstate;
> > >  	struct pwm_args pargs = { };
> > > -	int delta;
> > >  	int error;
> > >  
> > >  	pwm_get_args(haptic->pwm_dev, &pargs);
> > > -	delta = (pargs.period + haptic->pwm_duty) / 2;
> > > -	error = pwm_config(haptic->pwm_dev, delta, pargs.period);
> > > +	pwm_get_state(haptic->pwm_dev, &pstate);
> > > +
> > > +	pstate.period = pargs.period;
> > > +	pstate.duty_cycle = (pargs.period + haptic->pwm_duty) / 2;
> > > +	error = pwm_apply_state(haptic->pwm_dev, &pstate);
> > 
> > This does not make sense with regard to the atomic API. If you look in
> > max77693_haptic_play_work(), right after calling
> > max77693_haptic_set_duty_cycle() we either try to enable or disable the
> > pwm. When switching to this new API we should combine both actions.
> 
> True. I'll address that, unless Thierry is fine keeping the non-atomic
> API, in which case I'll just drop patches 32 to 46.

I'm fine with keeping the pwm_enable(), pwm_disable() and pwm_config()
APIs, but they should only be used as shortcuts. Where possible the new
atomic API should be used to combine multiple operations into one.

Thierry

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