Re: [PATCH 3/4] dt-bindings: arm: qcom,ids: Add a bunch of older SoCs

[Stephan Gerhold <stephan@gerhold.net>]

On Sun, Jan 08, 2023 at 03:40:52PM -0600, Rob Herring wrote:
> On Wed, Jan 04, 2023 at 12:53:47PM +0100, Stephan Gerhold wrote:
> > Sync the SoC IDs in qcom,ids.h with relevant entries from Qualcomm's LK
> > bootloader [1] that is used for almost all older Qualcomm SoCs.
> > 
> > Several of these are already supported, e.g.:
> >   - MSM8960 -> APQ8060, MSM8260, ...
> >   - MSM8976 -> APQ8076
> >   - MSM8956 -> APQ8056
> > Others are currently being worked on, e.g.:
> >   - MSM8909(W) -> APQ8009(W), MSM8905, MSM8209, ...
> >   - MSM8939 -> MSM8239, ...
> > 
> > And even all remaining ones added are close enough to what is already
> > supported so that future support is realistic (if someone steps up to
> > do the work).
> > 
> > Add all of them at once to avoid having to add them one by one in the
> > future. This will also benefit other projects making use of the same
> > dt-bindings, e.g. bootloaders where adding support for all these SoCs
> > is a bit easier than on Linux.
> 
> The promise was in accepting the properties upstream is we'd only be 
> adding these for bootloaders with dtbs that we can't otherwise update or 
> change.

qcom,ids.h contains all the SoC IDs, even ones not meant to be used in
the deprecated "qcom,msm-id" property. This is because it is also used
in the socinfo driver for example (that I'm also editing in this
series).

The actual allowlist for the "qcom,msm-id"/"qcom,board-id" is in
Documentation/devicetree/bindings/arm/qcom.yaml and is unchanged by this
patch series.

Still:

>
> Do all of those meet this criteria? Seems unlikely.
> 

All platforms added in this patch are older ones that do indeed require
the "qcom,msm-id"/"qcom,board-id" properties - except for the really
ancient ones that are still using ATAGS for booting.

However, there is no need to extend the allowlist to all these
platforms. We're circumventing the limitations of the Qualcomm
bootloader by "chainloading" another bootloader without those quirks
(right now mainly a modified version of Qualcomm's original bootloader,
but U-Boot also works on some of these platforms). That is why the
deprecated properties do not need to be present in the Linux DT.

Thanks,
Stephan