Re: [PATCH v3 00/12] usb: dwc3: qcom: Flatten dwc3 structure

Rob Herring
2025-01-14T17:44:53Z

On Mon, Jan 13, 2025 at 09:11:33PM -0800, Bjorn Andersson wrote:
> The USB IP-block found in most Qualcomm platforms is modelled in the
> Linux kernel as 3 different independent device drivers, but as shown by
> the already existing layering violations in the Qualcomm glue driver
> they can not be operated independently.
>
> With the current implementation, the glue driver registers the core and
> has no way to know when this is done. As a result, e.g. the suspend
> callbacks needs to guard against NULL pointer dereferences when trying
> to peek into the struct dwc3 found in the drvdata of the child.
>
> Missing from the upstream Qualcomm USB support is proper handling of
> role switching, in which the glue needs to be notified upon DRD mode
> changes. Several attempts has been made through the years to register
> callbacks etc, but they always fall short when it comes to handling of
> the core's probe deferral on resources etc.
>
> Furhtermore, the DeviceTree binding is a direct representation of the
> Linux driver model, and doesn't necessarily describe "the USB IP-block".
>
> This series therefor attempts to flatten the driver split, and operate
> the glue and core out of the same platform_device instance. And in order
> to do this, the DeviceTree representation of the IP block is flattened.
>
> To avoid littering the dwc3-qcom driver with the migration code - which
> we should be able to drop again in a LTS or two - this is now placed in
> drivers/of/overlays.
>
> A patch to convert a single platform - sc8280xp - is included in the
> series. The broader conversion will be submitted in a follow up series.

Is it not possible to use the same overlays also fixup the .dts files at
build time?

Rob