linux-kernel - [PATCH 5.3 081/148] DTS: ARM: gta04: introduce legacy spi-cs-high to make display work again

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Date:   Thu, 10 Oct 2019 10:35:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "H. Nikolaus Schaller" <hns@...delico.com>,
        Tony Lindgren <tony@...mide.com>
Subject: [PATCH 5.3 081/148] DTS: ARM: gta04: introduce legacy spi-cs-high to make display work again

From: H. Nikolaus Schaller <hns@...delico.com>

commit f1f028ff89cb0d37db299d48e7b2ce19be040d52 upstream.

commit 6953c57ab172 "gpio: of: Handle SPI chipselect legacy bindings"

did introduce logic to centrally handle the legacy spi-cs-high property
in combination with cs-gpios. This assumes that the polarity
of the CS has to be inverted if spi-cs-high is missing, even
and especially if non-legacy GPIO_ACTIVE_HIGH is specified.

The DTS for the GTA04 was orginally introduced under the assumption
that there is no need for spi-cs-high if the gpio is defined with
proper polarity GPIO_ACTIVE_HIGH.

This was not a problem until gpiolib changed the interpretation of
GPIO_ACTIVE_HIGH and missing spi-cs-high.

The effect is that the missing spi-cs-high is now interpreted as CS being
low (despite GPIO_ACTIVE_HIGH) which turns off the SPI interface when the
panel is to be programmed by the panel driver.

Therefore, we have to add the redundant and legacy spi-cs-high property
to properly activate CS.

Cc: stable@...r.kernel.org
Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
Signed-off-by: Tony Lindgren <tony@...mide.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/boot/dts/omap3-gta04.dtsi |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/arm/boot/dts/omap3-gta04.dtsi
+++ b/arch/arm/boot/dts/omap3-gta04.dtsi
@@ -120,6 +120,7 @@
 			spi-max-frequency = <100000>;
 			spi-cpol;
 			spi-cpha;
+			spi-cs-high;

 			backlight= <&backlight>;
 			label = "lcd";