linux-kernel - Re: [PATCH v3 04/12] backlight: pwm_bl: remove useless call to pwm_set

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Date:	Tue, 22 Sep 2015 23:12:18 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	linux-pwm@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jingoo Han <jingoohan1@...il.com>, linux-fbdev@...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>,
	linux-sunxi@...glegroups.com, Heiko Stuebner <heiko@...ech.de>,
	linux-rockchip@...ts.infradead.org,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Daniel Mack <daniel@...que.org>,
	Haojian Zhuang <haojian.zhuang@...il.com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Doug Anderson <dianders@...gle.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH v3 04/12] backlight: pwm_bl: remove useless call to
 pwm_set_period

On Mon, 21 Sep 2015, Boris Brezillon wrote:

> The PWM period will be set when calling pwm_config. Remove this useless
> call to pwm_set_period, which might mess up with the initial PWM state
> once we have added proper support for PWM init state retrieval.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> ---
>  drivers/video/backlight/pwm_bl.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)

Acked-by: Lee Jones <lee.jones@...aro.org>

> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index ae498c1..71944f8 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -293,12 +293,14 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  	 * period, parsed from the DT, in the PWM device. For the non-DT case,
>  	 * set the period from platform data if it has not already been set
>  	 * via the PWM lookup table.
> +	 * FIXME: This assignment should be dropped as soon as all the boards
> +	 * have moved to the PWM lookup table approach. The same goes for the
> +	 * pb->period field which should be replaced by
> +	 * pwm_get_default_period() calls.
>  	 */
>  	pb->period = pwm_get_default_period(pb->pwm);
> -	if (!pb->period && (data->pwm_period_ns > 0)) {
> +	if (!pb->period && (data->pwm_period_ns > 0))
>  		pb->period = data->pwm_period_ns;
> -		pwm_set_period(pb->pwm, data->pwm_period_ns);
> -	}
>  
>  	pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
>  

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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