[Letux-kernel] [RFC 1/2] Revert "DTS: ARM: gta04: introduce legacy spi-cs-high to make display work again"

[Andreas Kemnade]

Hi,

maybe make it also clear in the commit message, that our cs is low
active. It was not clear for me until I studied the schematics and the
datasheet.

In general the submitting patches document says:
"Describe your changes in imperative mood" There is a lot of "we" in
here. No idea whether someone cares.

On Wed,  2 Dec 2020 09:56:01 +0100
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> This reverts commit f1f028ff89cb.
> 
> commit 6953c57ab172 ("gpio: of: Handle SPI chipselect legacy bindings")
> 
The following paragraph is misinterpretative. I comment my
interpretation here, just from reading.

> 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,
so it would be low-active which would we just be what we need.

> even
> and especially if non-legacy GPIO_ACTIVE_HIGH is specified.
> 
which we have.

> As a result we had to introduce spi-cs-high to the device tree by
> 
if the above interpretation would be true, we would not need that.

> commit f1f028ff89cb ("DTS: ARM: gta04: introduce legacy spi-cs-high to make display work again")
> 
> Now,
> 
> commit 766c6b63aa04 ("spi: fix client driver breakages when using GPIO descriptors")
> 
> removes this inversion logic again and the GTA04 display is broken again.
> 
> So we have to revert the device tree change again.
> 
> But we should revert it only if
> 
> commit 766c6b63aa04 ("spi: fix client driver breakages when using GPIO descriptors")
> 
> is present in some kernel version. Hence this is the Fixes: reference
> and not the original change.
> 
> Fixes: 766c6b63aa04 ("spi: fix client driver breakages when using GPIO descriptors")
> CC: stable at vger.kernel.org
> Signed-off-by: H. Nikolaus Schaller <hns at goldelico.com>
> ---
>  arch/arm/boot/dts/omap3-gta04.dtsi | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/arm/boot/dts/omap3-gta04.dtsi b/arch/arm/boot/dts/omap3-gta04.dtsi
> index 432bbb21ddd05a..7c4c0124e20d45 100644
> --- a/arch/arm/boot/dts/omap3-gta04.dtsi
> +++ b/arch/arm/boot/dts/omap3-gta04.dtsi
> @@ -149,7 +149,6 @@ lcd: td028ttec1 at 0 {
>  			spi-max-frequency = <100000>;
>  			spi-cpol;
>  			spi-cpha;
> -			spi-cs-high;
>  
>  			backlight= <&backlight>;
>  			label = "lcd";