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

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Message-ID: <Z4FQ+XQYS7tpHs9b@lizhi-Precision-Tower-5810>
Date: Fri, 10 Jan 2025 11:55:21 -0500
From: Frank Li <Frank.li@....com>
To: Bjorn Andersson <quic_bjorande@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	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
Subject: Re: [PATCH v2 0/7] usb: dwc3: qcom: Flatten dwc3 structure

On Tue, Oct 08, 2024 at 07:54:48PM -0700, Bjorn Andersson wrote:
> On Tue, Oct 08, 2024 at 04:09:45PM -0400, Frank Li wrote:
> > 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?
> >
>
> Thanks for reaching out, Frank. I did pick this up again a few days
> back.
>
> I'm struggling with Rob's request for not peeking into struct property
> and/or utilizing overlays. Hoping to figure this out shortly, so I can
> get v3 in shape.

Bjorn:
	Do you still work on this? Or I missed somethings.

Frank

>
> Regards,
> Bjorn