linux-kernel - Re: [PATCH v5 34/46] clk: pwm: switch to the atomic API

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Date:	Wed, 30 Mar 2016 15:01:49 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	linux-pwm@...r.kernel.org,
	Mike Turquette <mturquette@...libre.com>,
	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>,
	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>,
	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>,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	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 34/46] clk: pwm: switch to the atomic API

On 03/30, Boris Brezillon wrote:
> diff --git a/drivers/clk/clk-pwm.c b/drivers/clk/clk-pwm.c
> index ebcd738..49ec5b1 100644
> --- a/drivers/clk/clk-pwm.c
> +++ b/drivers/clk/clk-pwm.c
> @@ -28,15 +28,29 @@ static inline struct clk_pwm *to_clk_pwm(struct clk_hw *hw)
>  static int clk_pwm_prepare(struct clk_hw *hw)
>  {
>  	struct clk_pwm *clk_pwm = to_clk_pwm(hw);
> +	struct pwm_state pstate;
>  
> -	return pwm_enable(clk_pwm->pwm);
> +	pwm_get_state(clk_pwm->pwm, &pstate);
> +	if (pstate.enabled)
> +		return 0;
> +
> +	pstate.enabled = true;
> +
> +	return pwm_apply_state(clk_pwm->pwm, &pstate);

This doesn't seem atomic anymore if we're checking the state and
then not calling apply_state if it's already enabled. But I
assume this doesn't matter because we "own" the pwm here?
Otherwise I would think this would be unconditional apply state
and duplicates would be ignored in the pwm framework.

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