* [PATCH v2] DTS: ARM: gta04: introduce legacy spi-cs-high to make display work again
@ 2019-09-20 16:11 H. Nikolaus Schaller
2019-09-23 17:34 ` Tony Lindgren
0 siblings, 1 reply; 2+ messages in thread
From: H. Nikolaus Schaller @ 2019-09-20 16:11 UTC (permalink / raw)
To: Benoît Cousson, Tony Lindgren, Rob Herring, Mark Rutland,
broonie, linus.walleij
Cc: stable, linux-spi, linux-omap, devicetree, linux-kernel,
letux-kernel, kernel, H. Nikolaus Schaller
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@vger.kernel.org
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
---
arch/arm/boot/dts/omap3-gta04.dtsi | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm/boot/dts/omap3-gta04.dtsi b/arch/arm/boot/dts/omap3-gta04.dtsi
index b295f6fad2a5..954c216140ad 100644
--- 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";
--
2.19.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] DTS: ARM: gta04: introduce legacy spi-cs-high to make display work again
2019-09-20 16:11 [PATCH v2] DTS: ARM: gta04: introduce legacy spi-cs-high to make display work again H. Nikolaus Schaller
@ 2019-09-23 17:34 ` Tony Lindgren
0 siblings, 0 replies; 2+ messages in thread
From: Tony Lindgren @ 2019-09-23 17:34 UTC (permalink / raw)
To: H. Nikolaus Schaller
Cc: Benoît Cousson, Rob Herring, Mark Rutland, broonie,
linus.walleij, stable, linux-spi, linux-omap, devicetree,
linux-kernel, letux-kernel, kernel
* H. Nikolaus Schaller <hns@goldelico.com> [190920 09:12]:
> 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.
Thanks applying into fixes.
Tony
^ permalink raw reply [flat|nested] 2+ messages in thread
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