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

From	YH Huang <yh.huang@mediatek.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] pwm-backlight: fix the panel power sequence
Date	2015-10-30 08:50 +0100
Message-ID	<qpcBH-30K-7@gated-at.bofh.it> (permalink)
References	<qk9l9-1PY-25@gated-at.bofh.it> <qk9Ev-2dv-17@gated-at.bofh.it> <qmpOO-6iz-17@gated-at.bofh.it> <qoXCG-23G-17@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi Hpilipp,

On Thu, 2015-10-29 at 16:40 +0100, Philipp Zabel wrote:
> Hi YH,
> 
> Am Donnerstag, den 22.10.2015, 23:12 +0800 schrieb YH Huang:
> > 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);
> 
> You are right.
> 
> > What do you think if I remove these two lines in my patch?
> > if (pb->enable_gpio)
> > 	gpiod_direction_output(pb->enable_gpio, 0);
> 
> 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);
}

I am not sure what "phandle" is working for.
My change is like your patch but remove the "phandle related" and
"gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT".
Do we really need these?

Also, do you think it is right that I do the "pwm_enable(pb->pwm);"
before "gpiod_set_value(pb->enable_gpio, 1);" in power on function?

Regards,
YH Huang

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Thread

Re: [PATCH v2] pwm-backlight: fix the panel power sequence YH Huang <yh.huang@mediatek.com> - 2015-10-22 17:20 +0200
  Re: [PATCH v2] pwm-backlight: fix the panel power sequence Philipp Zabel <p.zabel@pengutronix.de> - 2015-10-29 16:50 +0100
    Re: [PATCH v2] pwm-backlight: fix the panel power sequence YH Huang <yh.huang@mediatek.com> - 2015-10-30 08:50 +0100
      Re: [PATCH v2] pwm-backlight: fix the panel power sequence Philipp Zabel <p.zabel@pengutronix.de> - 2015-10-30 11:40 +0100

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