linux-kernel - Re: [PATCH v2 1/2] usb: dwc2: host: Fix missing device insertions

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Message-ID: <CAODwPW-O=ezdEWck1n4358ErK_6O5ksCeGY=KZi==f33_i3B9Q@mail.gmail.com>
Date:	Mon, 16 Nov 2015 12:26:26 -0800
From:	Julius Werner <jwerner@...omium.org>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Felipe Balbi <balbi@...com>,
	John Youn <John.Youn@...opsys.com>,
	Yunzhi Li <lyz@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Julius Werner <jwerner@...omium.org>,
	"Herrero, Gregory" <gregory.herrero@...el.com>,
	"Kaukab, Yousaf" <yousaf.kaukab@...el.com>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	John Youn <johnyoun@...opsys.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] usb: dwc2: host: Fix missing device insertions

Another point to note, which I think is what prevents the flow Alan
suggested from working, is this little snippet in DWC2's hub_control
GetPortStatus callback:

                if (!hsotg->flags.b.port_connect_status) {
                        /*
                         * The port is disconnected, which means the core is
                         * either in device mode or it soon will be.
Just
                         * return 0's for the remainder of the port status
                         * since the port register can't be read if the core
                         * is in device mode.
                         */
                        *(__le32 *)buf = cpu_to_le32(port_status);
                        break;
                }

This is before it actually checks the register state of the port. So
it relies on dwc2_hcd_connect() and dwc2_hcd_disconnect() to be called
in the right order to give the correct answer for
USB_PORT_STAT_CONNECTION. This could maybe be improved but I don't
know what kind of weird interactions with device mode operation made
that snippet necessary in the first place.
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