linux-kernel - Re: [PATCH v2] pwm-backlight: fix the panel power sequence

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Date:	Thu, 22 Oct 2015 23:12:30 +0800
From:	YH Huang <yh.huang@...iatek.com>
To:	Philipp Zabel <p.zabel@...gutronix.de>
CC:	Thierry Reding <thierry.reding@...il.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	<linux-pwm@...r.kernel.org>, <linux-fbdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	<linux-mediatek@...ts.infradead.org>,
	Sascha Hauer <kernel@...gutronix.de>,
	<yingjoe.chen@...iatek.com>,
	"Jean-Christophe Plagniol-Villard" <plagnioj@...osoft.com>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] pwm-backlight: fix the panel power sequence

On Fri, 2015-10-16 at 11:36 +0200, Philipp Zabel wrote:
> Am Freitag, den 16.10.2015, 17:17 +0800 schrieb YH Huang:
> > In order to match the panel power sequence, disable the enable_gpio
> > in the probe function. Also, reorder the code in the power_on and
> > power_off function to match the timing.
> 
> Could you also have a look at the "pwm-backlight: Avoid backlight
> flicker when probed from DT" patch?
> I think in case of a panel left enabled by the bootloader, your patch
> will disable the backlight for a short time.
> 
> best regards
> Philipp
> 
In the case of the panel disabled by the bootloader,
your patch still has the following code and always enables the backlight
in the probe function.
pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
-						  GPIOD_OUT_HIGH);

What do you think if I remove these two lines in my patch?
if (pb->enable_gpio)
	gpiod_direction_output(pb->enable_gpio, 0);


Regards,
YH Huang

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