linux-kernel - Re: [PATCH v6 0/6] usb: dwc3: qcom: Flatten dwc3 structure

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Message-ID: <2025041135-sanitizer-desolate-67cb@gregkh>
Date: Fri, 11 Apr 2025 15:43:49 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Bjorn Andersson <bjorn.andersson@....qualcomm.com>
Cc: 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>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>, Frank Li <Frank.li@....com>,
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 0/6] usb: dwc3: qcom: Flatten dwc3 structure

On Thu, Apr 10, 2025 at 10:50:11PM -0500, 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.
> 
> Departing from previous versions' attempts at runtime-convert the
> Devicetree representation is swapped out and instead a snapshot of the
> current dwc3-qcom driver is proposed to be carried for a limited time.
> 
> A patch to convert a single platform - sc8280xp - was included in the
> series. This, and others, will be submitted in a separate series as soon
> as its introduction won't break bisection.

Doesn't apply to my usb-next branch, can you rebase and resend?

thanks,

greg k-h