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

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Message-ID: <ZrugxSqzhzxvVqV3@lizhi-Precision-Tower-5810>
Date: Tue, 13 Aug 2024 14:07:01 -0400
From: Frank Li <Frank.li@....com>
To: Bjorn Andersson <andersson@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Felipe Balbi <balbi@...nel.org>,
	Wesley Cheng <quic_wcheng@...cinc.com>,
	Saravana Kannan <saravanak@...gle.com>,
	Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Konrad Dybcio <konrad.dybcio@...aro.org>, linux-usb@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	Bjorn Andersson <quic_bjorande@...cinc.com>
Subject: Re: [PATCH v2 0/7] usb: dwc3: qcom: Flatten dwc3 structure

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.

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@...cinc.com>
>