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

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Date:	Thu, 22 Oct 2015 23:29:02 +0800
From:	YH Huang <yh.huang@...iatek.com>
To:	Lucas Stach <l.stach@...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: [RESEND PATCH] pwm-backlight: fix the panel power sequence

On Fri, 2015-10-16 at 10:31 +0200, Lucas Stach wrote:
> Am Freitag, den 16.10.2015, 09:37 +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.
> > 
> You aren't specifying which panels power sequence you are matching here.
> Are you sure you aren't breaking other panels with this patch?
> 
> Regards,
> Lucas
The panel sequence is:
When powering on the panel, generate pwm signals fist and then enable it
to show the backlight.
When powering off the panel, do it opposite.
In probe function, we keep the panel status from bootloader and don't
enable or disable it by default.

Do these changes break other panels?

Regards,
YH Huang


> 
> > Signed-off-by: YH Huang <yh.huang@...iatek.com>
> > ---
> >  drivers/video/backlight/pwm_bl.c |   15 +++++++++------
> >  1 file changed, 9 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> > index eff379b..99eca1e 100644
> > --- a/drivers/video/backlight/pwm_bl.c
> > +++ b/drivers/video/backlight/pwm_bl.c
> > @@ -54,10 +54,11 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
> >  	if (err < 0)
> >  		dev_err(pb->dev, "failed to enable power supply\n");
> >  
> > +	pwm_enable(pb->pwm);
> > +
> >  	if (pb->enable_gpio)
> >  		gpiod_set_value(pb->enable_gpio, 1);
> >  
> > -	pwm_enable(pb->pwm);
> >  	pb->enabled = true;
> >  }
> >  
> > @@ -66,12 +67,12 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
> >  	if (!pb->enabled)
> >  		return;
> >  
> > -	pwm_config(pb->pwm, 0, pb->period);
> > -	pwm_disable(pb->pwm);
> > -
> >  	if (pb->enable_gpio)
> >  		gpiod_set_value(pb->enable_gpio, 0);
> >  
> > +	pwm_config(pb->pwm, 0, pb->period);
> > +	pwm_disable(pb->pwm);
> > +
> >  	regulator_disable(pb->power_supply);
> >  	pb->enabled = false;
> >  }
> > @@ -241,8 +242,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> >  	pb->dev = &pdev->dev;
> >  	pb->enabled = false;
> >  
> > -	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
> > -						  GPIOD_OUT_HIGH);
> > +	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable");
> >  	if (IS_ERR(pb->enable_gpio)) {
> >  		ret = PTR_ERR(pb->enable_gpio);
> >  		goto err_alloc;
> > @@ -264,6 +264,9 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> >  		pb->enable_gpio = gpio_to_desc(data->enable_gpio);
> >  	}
> >  
> > +	if (pb->enable_gpio)
> > +		gpiod_direction_output(pb->enable_gpio, 0);
> > +
> >  	pb->power_supply = devm_regulator_get(&pdev->dev, "power");
> >  	if (IS_ERR(pb->power_supply)) {
> >  		ret = PTR_ERR(pb->power_supply);
> 


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