linux-kernel - Re: [PATCH 00/12] usb: dwc3: qcom: Flatten dwc3 structure

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Message-ID: <20231020220432.sutkinakkd6ncuej@synopsys.com>
Date:   Fri, 20 Oct 2023 22:04:48 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
CC:     Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Felipe Balbi <balbi@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Johan Hovold <johan@...nel.org>,
        Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
Subject: Re: [PATCH 00/12] usb: dwc3: qcom: Flatten dwc3 structure

Hi Bjorn,

On Mon, Oct 16, 2023, 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.
> 
> As a side effect, much of the ACPI integration code is dropped.
> 
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> ---
> Bjorn Andersson (12):
>       dt-bindings: usb: qcom,dwc3: Add qcom,sc8180x-dwc3
>       usb: dwc3: qcom: Rename dwc3 platform_device reference
>       usb: dwc3: qcom: Merge resources from urs_usb device
>       usb: dwc3: Expose core driver as library
>       usb: dwc3: Override end of dwc3 memory resource
>       usb: dwc3: qcom: Add dwc3 core reference in driver state
>       usb: dwc3: qcom: Instantiate dwc3 core directly
>       usb: dwc3: qcom: Inline the qscratch constants
>       dt-bindings: usb: qcom,dwc3: Rename to "glue"
>       dt-bindings: usb: qcom,dwc3: Introduce flattened qcom,dwc3 binding
>       usb: dwc3: qcom: Flatten the Qualcomm dwc3 binding and implementation
>       arm64: dts: qcom: sc8180x: flatten usb_sec node
> 
>  .../devicetree/bindings/usb/qcom,dwc3-glue.yaml    | 626 +++++++++++++++++++++
>  .../devicetree/bindings/usb/qcom,dwc3.yaml         | 321 ++++-------
>  .../devicetree/bindings/usb/snps,dwc3.yaml         |  14 +-
>  .../arm64/boot/dts/qcom/sc8180x-lenovo-flex-5g.dts |   6 +-
>  arch/arm64/boot/dts/qcom/sc8180x-primus.dts        |   6 +-
>  arch/arm64/boot/dts/qcom/sc8180x.dtsi              |  34 +-
>  drivers/usb/dwc3/core.c                            | 136 +++--
>  drivers/usb/dwc3/core.h                            |  10 +
>  drivers/usb/dwc3/dwc3-qcom.c                       | 328 ++++++-----
>  9 files changed, 1057 insertions(+), 424 deletions(-)
> ---
> base-commit: 4d0515b235dec789578d135a5db586b25c5870cb
> change-id: 20231016-dwc3-refactor-931e3b08a8b9
> 
> Best regards,
> -- 
> Bjorn Andersson <quic_bjorande@...cinc.com>
> 

First of all, thanks for the work.

I just did a quick review through the changes, and I think it's great!
(This will address some issues I also have with dwc3 currently too.)

BR,
Thinh