From mboxrd@z Thu Jan  1 00:00:00 1970
From: Lothar =?UTF-8?B?V2HDn21hbm4=?= <LW@KARO-electronics.de>
Subject: Re: [PATCH v3] pwm: imx: Let PWM be active during suspend
Date: Mon, 11 Dec 2017 17:52:50 +0100
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To: Fabio Estevam <festevam@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>, linux-pwm@vger.kernel.org, Rob Herring <robh@kernel.org>, Russell King <linux@arm.linux.org.uk>, Fabio Estevam <fabio.estevam@nxp.com>, Lukasz Majewski <lukma@denx.de>

Hi,

On Mon, 11 Dec 2017 14:06:31 -0200 Fabio Estevam wrote:
> Hi Lothar,
> 
> On Mon, Dec 11, 2017 at 1:55 PM, Lothar Waßmann <LW@karo-electronics.de> wrote:
> 
> >> 1. Set the STOPEN bit which is what I do in this patch
> >>
> > This should probably work.
> > But this won't fix the issue, that the LED or backlight is turned fully
> > on when the brightness value is set to 0, since both the leds-pwm and
> > the pwmbl driver explicitly disable the PWM, when the brightness
> > value is set to 0.
> 
> Yes, but in the case of imx6qdl-cubox-i.dtsi the PWM is used in the
> normal polarity and the inversion is achieved via 'active-low'
> property of pwm-leds.
> 
> On this board the current dts + current pwm-imx driver behaves
> incorrecly only during suspend (LED is on). During normal mode the PWM
> operation is correct.
> 
> By setting the STOPEN bit the LED is off in suspend.
> 
> >> 2. Add support for allowing changing pinctrl in suspend:
> >> https://pastebin.com/71UGrnkA
> >>
> >> This way we can configure the pwm output pin as Hi-Z during suspend.
> >>
> >> What do you think?
> >>
> > It would be better to enable the 22K pullup on the pin. Otherwise the
> > pin will be floating when there is no external pullup resistor.
> 
> Yes, but first we need to come to a conclusion if we go with solution
> 1 (enable STOPEN) or with solution 2 (allow changinh pinctrl) :-)
> 
> I am more inclined to go with solution 1 as this was also used in the
> old vendor 3.0.35 kernel:
> http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/tree/arch/arm/plat-mxc/pwm.c?h=imx_3.0.35_4.1.0#n106
> 
> Please let me know what you prefer.
> 
I also prefer the patch that doesn't mess with the pin configs.


Lothar Waßmann