Re: [PATCH v8 6/9] usb: dwc3: qcom: Add multiport controller support for qcom wrapper

From: Johan Hovold <johan@kernel.org>
To: Krishna Kurapati PSSNV <quic_kriskura@quicinc.com>
Cc: Bjorn Andersson <andersson@kernel.org>,
	Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Andy Gross <agross@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Felipe Balbi <balbi@kernel.org>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
	quic_pkondeti@quicinc.com, quic_ppratap@quicinc.com,
	quic_wcheng@quicinc.com, quic_jackp@quicinc.com,
	quic_harshq@quicinc.com, ahalaney@redhat.com
Subject: Re: [PATCH v8 6/9] usb: dwc3: qcom: Add multiport controller support for qcom wrapper
Date: Thu, 8 Jun 2023 11:44:41 +0200	[thread overview]
Message-ID: <ZIGjCS-D7-kAQCJh@hovoldconsulting.com> (raw)
In-Reply-To: <3010d855-86b0-f87a-5eb7-85204be9b4b0@quicinc.com>

On Thu, Jun 08, 2023 at 01:25:25AM +0530, Krishna Kurapati PSSNV wrote:
> On 6/7/2023 5:14 PM, Johan Hovold wrote:
> > On Fri, May 26, 2023 at 08:55:22PM +0530, Krishna Kurapati PSSNV wrote:
> >> On 5/26/2023 8:25 AM, Bjorn Andersson wrote:
> > 
> >>> We need to fix the dwc3 glue design, so that the glue and the core can
> >>> cooperate - and we have a few other use cases where this is needed (e.g.
> >>> usb_role_switch propagation to the glue code).
> > 
> >>     Thanks for the comments on this patch. I had some suggestions come in
> >> from the team internally:
> >>
> >> 1. To use the notifier call available in drivers/usb/core/notify.c and
> >> make sure that host mode is enabled. That way we can access dwc or xhci
> >> without any issue.
> > 
> > I don't think this is a good idea and instead the callbacks should be
> > dedicated for the xhci and dwc3 drivers. A struct with callbacks can be
> > passed down to the child devices, which call back into the drivers of
> > their parents for notifications and when they need services from them
> > (e.g. during suspend or on role changes).

>    While I agree with you that these notifications are to be used during 
> role switch or suspend/resume, there is no restriction on using them for 
> checking whether we are in host mode or not. IMO, it would be cleaner as 
> we won't be dereferencing dwc driver data at all to check if we are in 
> host mode or not.

I'm not sure I understand what you're saying here. Could you try to
rephrase it?

Johan