Message-ID: <1446538299.2449.8.camel@mtksdaap41>
Subject: Re: [PATCH v2] pwm-backlight: fix the panel power sequence
From: YH Huang <yh.huang@mediatek.com>
To: Philipp Zabel <p.zabel@pengutronix.de>
CC: <linux-pwm@vger.kernel.org>, <linux-fbdev@vger.kernel.org>,
        Jingoo Han <jingoohan1@gmail.com>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
        <linux-kernel@vger.kernel.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        <linux-mediatek@lists.infradead.org>,
        Sascha Hauer <kernel@pengutronix.de>,
        Matthias Brugger <matthias.bgg@gmail.com>, <yingjoe.chen@mediatek.com>,
        "Lee Jones" <lee.jones@linaro.org>,
        <linux-arm-kernel@lists.infradead.org>
Date: Tue, 3 Nov 2015 16:11:39 +0800
In-Reply-To: <1446201271.3334.22.camel@pengutronix.de>
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On Fri, 2015-10-30 at 11:34 +0100, Philipp Zabel wrote:
> Am Freitag, den 30.10.2015, 15:41 +0800 schrieb YH Huang:
> > > That won't work if the gpio is still configured as input. How about I
> > > add the GPIOD_ASIS change to my patch you remove that and the above from
> > > yours?
> > 
> > I revise these two lines 
> > if (pb->enable_gpio)
> > 	gpiod_direction_output(pb->enable_gpio, 0);
> > into
> > if (pb->enable_gpio) {
> > 	if(gpiod_get_value(pb->enable_gpio) == 0)
> > 		gpiod_direction_output(pb->enable_gpio, 0);
> > 	else
> > 		gpiod_direction_output(pb->enable_gpio, 1);
> > }
> 
> If the GPIO is still configured as an input, the return value of
> gpiod_get_value could be random.
> 
> > I am not sure what "phandle" is working for.
> 
> The reasoning is that devices where there is no phandle link pointing to
> the backlight (for example from a simple-panel node), we should keep the
> current default behaviour (enable during probe).

I have a little problem for the current default behaviour.
Should we enable during probe?

Before this patch ( http://patchwork.ozlabs.org/patch/324690/ ),
we disable "enable-gpio" in the probe function.

Do you have any idea of this?

Regards,
YH Huang


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