Re: [PATCH v2 0/7] usb: dwc3: qcom: Flatten dwc3 structure

Frank Li
2024-10-08T20:09:57Z

On Tue, Aug 13, 2024 at 02:07:01PM -0400, Frank Li wrote:
> On Sun, Aug 11, 2024 at 08:11:57PM -0700, 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 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.
>

Bjorn Andersson:
Any follow up on this thread?

Frank

> Thanks, we faced the same problem. Can you cc me next time?
>
> Frank
> >
> > ---
> > Changes in v2:
> > - Rewrite after ACPI removal, multiport support and interrupt fixes
> > - Completely changed strategy for DeviceTree binding, as previous idea
> > of using snps,dwc3 as a generic fallback required unreasonable changes
> > to that binding.
> > - Abandoned idea of supporting both flattened and unflattened device
> > model in the one driver. As Johan pointed out, it will leave the race
> > condition holes and will make the code harder to understand.
> > Furthermore, the role switching logic that we intend to introduce
> > following this would have depended on the user updating their
> > DeviceTree blobs.
> > - Per above, introduced the dynamic DeviceTree rewrite
> > - Link to v1: https://lore.kernel.org/all/20231016-dwc3-refactor-v1-0-ab4a84165470@quicinc.com/
> >
> > ---
> > Bjorn Andersson (7):
> > dt-bindings: usb: snps,dwc3: Split core description
> > dt-bindings: usb: Introduce qcom,snps-dwc3
> > of: dynamic: Don't discard children upon node attach
> > usb: dwc3: core: Expose core driver as library
> > usb: dwc3: qcom: Don't reply on drvdata during probe
> > usb: dwc3: qcom: Transition to flattened model
> > arm64: dts: qcom: sc8280x: Flatten the USB nodes
> >
> > .../devicetree/bindings/usb/qcom,dwc3.yaml | 13 +-
> > .../devicetree/bindings/usb/qcom,snps-dwc3.yaml | 608 +++++++++++++++++++++
> > .../devicetree/bindings/usb/snps,dwc3-common.yaml | 417 ++++++++++++++
> > .../devicetree/bindings/usb/snps,dwc3.yaml | 391 +------------
> > arch/arm64/boot/dts/qcom/sa8295p-adp.dts | 12 +-
> > arch/arm64/boot/dts/qcom/sa8540p-ride.dts | 5 +-
> > arch/arm64/boot/dts/qcom/sc8280xp-crd.dts | 12 +-
> > .../dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts | 11 +-
> > arch/arm64/boot/dts/qcom/sc8280xp.dtsi | 138 +++--
> > drivers/of/dynamic.c | 1 -
> > drivers/usb/dwc3/core.c | 169 ++++--
> > drivers/usb/dwc3/core.h | 3 +
> > drivers/usb/dwc3/dwc3-qcom.c | 323 ++++++++---
> > 13 files changed, 1483 insertions(+), 620 deletions(-)
> > ---
> > base-commit: 864b1099d16fc7e332c3ad7823058c65f890486c
> > change-id: 20231016-dwc3-refactor-931e3b08a8b9
> >
> > Best regards,
> > --
> > Bjorn Andersson <quic_bjorande@quicinc.com>
> >