Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 1 Dec 2020 17:44:33 +0100
From:   Andreas Kemnade <andreas@kemnade.info>
To:     Sven Van Asbroeck <thesven73@gmail.com>
Cc:     Discussions about the Letux Kernel <letux-kernel@openphoenux.org>,
        "H. Nikolaus Schaller" <hns@goldelico.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Mark Brown <broonie@kernel.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Subject: Re: [Letux-kernel] [BUG] SPI broken for SPI based panel drivers
Message-ID: <20201201174433.2000c8a3@aktux>
In-Reply-To: <CAGngYiUG76Q-cb_HdDKMia5yXzv_mS+5NPeaBquK3_4b3tr-4Q@mail.gmail.com>
References: <2D7916FA-678F-4236-B478-C953CADF2FFA@goldelico.com>
        <CAGngYiXgc_m2A7Wihxuhzm-u4qH-JZgxHjke653zvyT45jMU7Q@mail.gmail.com>
        <4AC29229-9542-4E77-B993-217E29C7E209@goldelico.com>
        <20201201121620.GB5239@sirena.org.uk>
        <A499CCB9-F2EC-4F24-AA79-5A7FA6A092A9@goldelico.com>
        <CACRpkdYf2dUF6PjYcvnsKDPoxXPWiWKKAqpik4-2AAQjRmatfw@mail.gmail.com>
        <6283C16F-549C-4463-BC08-E2C1A1D78B2F@goldelico.com>
        <CAGngYiUG76Q-cb_HdDKMia5yXzv_mS+5NPeaBquK3_4b3tr-4Q@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Tue, 1 Dec 2020 11:10:49 -0500
Sven Van Asbroeck <thesven73@gmail.com> wrote:

> Nikolaus,
> 
> On Tue, Dec 1, 2020 at 9:38 AM H. Nikolaus Schaller <hns@goldelico.com> wrote:
> >
> > Let's work on a fix for the fix now.
> >  
> 
> Are you quite sure the chip-select of the tpo,td028ttec1 panel
> is active-high? A quick google produced a datasheet which
> seems to indicate that XCS is active-low?
> 
Schematics is here:
https://projects.goldelico.com/p/gta04-main/downloads/48/

The display connector P204-LCD indicates some inversion at the XCS and
XRES pins.

This patch fixes things for a boot where the display was not
touched by the bootloader
diff --git a/arch/arm/boot/dts/omap3-gta04.dtsi b/arch/arm/boot/dts/omap3-gta04.dtsi
index c8745bc800f7..003202d12990 100644
--- a/arch/arm/boot/dts/omap3-gta04.dtsi
+++ b/arch/arm/boot/dts/omap3-gta04.dtsi
@@ -124,7 +124,6 @@
                        spi-max-frequency = <100000>;
                        spi-cpol;
                        spi-cpha;
-                       spi-cs-high;
 
                        backlight= <&backlight>;
                        label = "lcd";

So if that one is really active-low, why did it ever work?!

Regards,
Andreas