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
