linux-kernel - Re: [PATCH] ARM: dts: Add empty "chosen" node to WM8xxx device trees

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Message-ID: <20201024210910.GA27207@arch-xps.localdomain>
Date:   Sat, 24 Oct 2020 15:09:10 -0600
From:   Brigham Campbell <me@...ghamcampbell.com>
To:     robh+dt@...nel.org, robh@...nel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, alchark@...il.com
Subject: Re: [PATCH] ARM: dts: Add empty "chosen" node to WM8xxx device trees

On Fri, Oct 09, 2020 at 10:57:42AM -0600, Brigham Campbell wrote:
> The following patch is a bug fix for an issue introduced by commit
> abe60a3a7afb4058278864aa18c5faf62094c11a which removed the deprecated
> device tree skeletons.
> 
> For the devices corresponding to these device trees, an updated version
> of U-Boot is not available. Therefore, we must append DTBs to the kernel
> instead of counting on the bootloader to load one into memory and pass
> the pointer to the kernel during init.
> 
> For some reason, when this method of appending DTBs to the kernel is
> used with any revision after abe60a3a7, the DTB seems to load correctly,
> but the kernel parameters aren't loaded correctly. Regardless of whether
> the kernel parameters are built into the kernel or passed in via U-Boot,
> they simply aren't registered by the running kernel.
> 
> Adding an empty "chosen" node to the device tree fixes this issue. I've
> tested this with a WM8650-based laptop. Regrettably, I'd be lying if I
> said that I know exactly why this fixes the problem. However, I know
> that this solution works. I'm happy to hear suggestions/ridicule
> regarding these changes.
> 
> Finally, I have my suspicions that the WM8xxx series devices aren't the
> only ones affected by this issue. I think this solution, if acceptable,
> could be applied to other devices which may or may not be having issues
> related to appended DTBs and kernel parameters. Perhaps other devices
> which commit abe60a3a7 changed?
> 
> This is my first patch submission to the Linux kernel, so please tear it
> apart. Let me know what I've done incorrectly. And thanks, Alexey, for
> helping me along. I have much to learn and I wouldn't have made it half
> as far without his patience.
> 
> Thanks,
> Brigham Campbell
> 
> Signed-off-by: Brigham Campbell <me@...ghamcampbell.com>
> 
> ---
>  arch/arm/boot/dts/wm8505.dtsi | 2 ++
>  arch/arm/boot/dts/wm8650.dtsi | 2 ++
>  arch/arm/boot/dts/wm8850.dtsi | 2 ++
>  3 files changed, 6 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/wm8505.dtsi b/arch/arm/boot/dts/wm8505.dtsi
> index 168cd12b07bc..2b814b48b458 100644
> --- a/arch/arm/boot/dts/wm8505.dtsi
> +++ b/arch/arm/boot/dts/wm8505.dtsi
> @@ -10,6 +10,8 @@ / {
>  	#size-cells = <1>;
>  	compatible = "wm,wm8505";
>  
> +	chosen {};
> +
>  	cpus {
>  		#address-cells = <0>;
>  		#size-cells = <0>;
> diff --git a/arch/arm/boot/dts/wm8650.dtsi b/arch/arm/boot/dts/wm8650.dtsi
> index bc057b6f7d16..a68c82c8035e 100644
> --- a/arch/arm/boot/dts/wm8650.dtsi
> +++ b/arch/arm/boot/dts/wm8650.dtsi
> @@ -10,6 +10,8 @@ / {
>  	#size-cells = <1>;
>  	compatible = "wm,wm8650";
>  
> +	chosen {};
> +
>  	cpus {
>  		#address-cells = <0>;
>  		#size-cells = <0>;
> diff --git a/arch/arm/boot/dts/wm8850.dtsi b/arch/arm/boot/dts/wm8850.dtsi
> index 65c9271050e6..c864883ae777 100644
> --- a/arch/arm/boot/dts/wm8850.dtsi
> +++ b/arch/arm/boot/dts/wm8850.dtsi
> @@ -10,6 +10,8 @@ / {
>  	#size-cells = <1>;
>  	compatible = "wm,wm8850";
>  
> +	chosen {};
> +
>  	cpus {
>  		#address-cells = <1>;
>  		#size-cells = <0>;
> -- 
> 2.28.0
> 

Sorry to generate another notification, but I don't believe I've
recieved a response on this patch in the ~two weeks it's been up. Did I
format something incorrectly or have I sent it to the wrong addresses?
Maybe the relevant maintainer has just been busy?

Thanks,
Brigham Campbell