linux-kernel - Re: [BUG/PATCH 1/4] DTS: GTA04: SPI / gpiolib: work around a regression that unhides a broken legacy handler, which makes the gta04 display inoperable

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Message-Id: <06C7464E-FAF2-4AA6-9FF4-629E9C97F86A@goldelico.com>
Date:   Mon, 1 Apr 2019 18:56:51 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Benoît Cousson <bcousson@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-omap@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        letux-kernel@...nphoenux.org
Subject: Re: [BUG/PATCH 1/4] DTS: GTA04: SPI / gpiolib: work around a regression that unhides a broken legacy handler, which makes the gta04 display inoperable

Hi Tony,

> Am 01.04.2019 um 18:46 schrieb Tony Lindgren <tony@...mide.com>:
> 
> Hi,
> 
> * H. Nikolaus Schaller <hns@...delico.com> [190331 10:08]:
>> This is an ugly workaround for a regression introduced into v5.1-rc1 by
>> 
>> <c1c04cea13dc234ce9a4504879ddd36ea524d880>
> 
> You should standardized commit references like this instead:
> 
> c1c04cea13dc ("gpio: of: Fix logic inversion")
> 
> Then please also include a proper Fixes tag.
> 
> You can configure an alias for it to make things easier:
> 
> git log --abbrev=12 --pretty=format:"%h (\"%s\")"
> 
>> --- a/arch/arm/boot/dts/omap3-gta04.dtsi
>> +++ b/arch/arm/boot/dts/omap3-gta04.dtsi
>> @@ -114,6 +114,7 @@
>> 		gpio-miso = <&gpio1 18 GPIO_ACTIVE_HIGH>;
>> 		gpio-mosi = <&gpio1 20 GPIO_ACTIVE_HIGH>;
>> 		cs-gpios = <&gpio1 19 GPIO_ACTIVE_HIGH>;
>> +		spi-cs-high;	/* make the legacy handler in gpiolib not intervene */
>> 		num-chipselects = <1>;
>> 
>> 		/* lcd panel */
>> @@ -123,6 +124,7 @@
>> 			spi-max-frequency = <100000>;
>> 			spi-cpol;
>> 			spi-cpha;
>> +			spi-cs-high;	/* here is where it should be but this is ignored by a bug in the gpiolib handler */
>> 
>> 			backlight= <&backlight>;
>> 			label = "lcd";
> 
> So what's the plan with this fix? Add this for v5.2-rc cycle,
> then revert it later? I'd probably go directly for the proper
> fix if possible.

Well, I learned just some minutes ago that a new patch for gpiolib
came through 5.1-rc3 which does fix this.

It seems to check for "cs-gpios" and then disable the legacy handling.

This means that we do not need to patch the DTS at all.

BR and thanks,
Nikolaus