[PATCH 00/21] Qualcomm generic board support

[ff]

Le 5 déc. 2023 à 13:48, Daniel Thompson <daniel.thompson at linaro.org> a écrit :

On Tue, Dec 05, 2023 at 10:36:28AM +0000, ff wrote:
Le 5 déc. 2023 à 10:46, Sumit Garg <sumit.garg at linaro.org> a écrit :

+ U-boot custodians list

On Tue, 5 Dec 2023 at 12:58, Krzysztof Kozlowski
<krzysztof.kozlowski at linaro.org> wrote:

On 05/12/2023 08:13, Sumit Garg wrote:
@DT bindings maintainers,

Given the ease of maintenance of DT bindings within Linux kernel
source tree, I don't have a specific objection there. But can we
ease DTS testing for firmware/bootloader projects by providing a
versioned release package for DT bindings? Or if someone else
has a better idea here please feel free to chime in.

This doesn't work for you?:

https://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git/

Thanks, this is certainly a good step which I wasn't aware of.
Further simplification can be done to decouple devicetree source
files from DT bindings.

Why?

I suppose you are already aware that Linux DTS files are a subset of
what could be supported by devicetree schemas. There can be
firmware/bootloader specific properties (one example being [1])
which Linux kernel can simply ignore. Will you be willing to add all
of those DT properties to Linux DTS files and maintain them?

A pre-existing effort to solve the same problem as [1] is System
Device Tree, discussed in the context of Linaro supported OpenAMP
project. It is not just about cherry picking devices that have
bindings in Linux but also information about clock and power domains
or devices that are not seen by Linux.  It is obvious that the
resulting bindings should be maintained upstream in the DT repo
regardless of the communities adopted solution.

This seems to be artificially linking two topics: system DT and DT
schema validation within u-boot. They are somewhat related but one of
not a precondition of the other.

Agreed. I am mentioning this because it relates to binding
and conformance testing:   DT consumers such as OP-TEE , OSes and
hypervisors should be considered equally as U-Boot and Linux.
Hence it makes sense that all those are decoupled from any
consumer and live « standalone ».


However, DT bindings are something which should be common, the
hardware description of a device should be universal. IMO, splitting
DT bindings alone would ease the compliance process for u-boot
drivers in quite similar manner to Linux drivers.

I remember a discussion with ST on that topic related to Framebuffer.
U-Boot can need a very different representation of the same device to
use it while Linux need an in-depth description of all shaders and «
stuff » (another reason why [1] is addressing only a portion of the
problem) So even if there is a single frame buffer binding, there
should be two (at least) conformance tests.

I don't follow this, for two reasons.

1. DT describes the hardware, not how it is driven. Having a relationship
  between u-boot and linux DTs with different representation would
  imply that the hardware changes between u-boot and the kernel.

2. Even if we were to accept that there must be two device tree instances
  (beyond transient workarounds for missing features), why would there
  need to be two conformance tests rather than one conformance test run
  on the two DTs?

Let’s say U-Boot only cares and use legacy SGVA frame buffer, while Linux
 community only cares and use the full fledged GPU. You end-up with two
communities maintaining the conformance test part it cares/need.
Isn’t splitting the tests responsibilities a way to get people feel
more « empowered » and thus more active?


Daniel.