linux-kernel - Re: Backporting commits for generating rpi dtb symbols to stable

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Message-ID: <2023071644-earflap-amazingly-3989@gregkh>
Date:   Sun, 16 Jul 2023 18:32:42 +0200
From:   Greg KH <greg@...ah.com>
To:     Pali Rohár <pali@...nel.org>
Cc:     Aurelien Jarno <aurelien@...el32.net>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        stable@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Backporting commits for generating rpi dtb symbols to stable

On Sun, Jul 16, 2023 at 06:24:44PM +0200, Pali Rohár wrote:
> Hello,
> 
> I see that raspberry pi bootloader throws ton of warnings when supplied
> DTB file does not contain /__symbols__/ node.
> 
> On RPI 1B rev1 it looks like this:
> 
> dterror: no symbols found
> dterror: no symbols found
> dterror: no symbols found
> dterror: no symbols found
> dterror: no symbols found
> dterror: no symbols found
> dterror: no symbols found
> dterror: no symbols found
> dterror: no symbols found
> dterror: no symbols found
> 
> Bootloader also propagates these warnings to kernel via dtb property
> chosen/user-warnings and they can be read by simple command:
> 
> $ cat /sys/firmware/devicetree/base/chosen/user-warnings
> ...
> 
> Upstream Linux kernel build process by default does not generate
> /__symbols__/ node for DTB files, but DTB files provided by raspberrypi
> foundation have them for a longer time.
> 
> I wanted to look at this issue, but I figured out that it is already
> solved by just recent Aurelien's patches:
> 
> e925743edc0d ("arm: dts: bcm: Enable device-tree overlay support for RPi devices")
> 3cdba279c5e9 ("arm64: dts: broadcom: Enable device-tree overlay support for RPi devices")
> 
> My testing showed that /__symbols__/ node is required by rpi bootloader
> for overlay support even when overlayed DTB file does not use any DTB
> symbol (and reference everything via full node path). So seems that
> /__symbols__/ node is crucial for rpi bootloader even when symbols from
> them are not used at all.
> 
> So I would like to ask, would you consider backporting these two
> raspberry pi specific patches to stable kernel trees? Upstream kernel
> would get rid of those bootloader warnings and also allow users to use
> overlayed dtbs...

What kernel tree(s) should these be applied to?  What trees did you test
them for?

Also, adding dt-overlay support does not seem like a stable kernel fix,
as this isn't a bugfix from what I can tell, right?

thanks,

greg k-h