linux-kernel - Re: ChipIdea USB regression

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Message-ID: <20220114111800.GL18506@ediswmail.ad.cirrus.com>
Date:   Fri, 14 Jan 2022 11:18:00 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     <robh@...nel.org>
CC:     <peter.chen@...nel.org>, <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: ChipIdea USB regression

On Fri, Jan 14, 2022 at 10:56:20AM +0000, Charles Keepax wrote:
> Hi guys,
> 
> My Zynq based board stopped booting today, a bisect points to this
> patch:
> 
> commit 0f153a1b8193 ("usb: chipidea: Set the DT node on the child device")
> 
> It looks like it gets stuck in some sort of boot loop of doom:

Ok so poking that a little more, I think I can see what happens,
the USB DT node looks like this:

usb0: usb@...02000 {
	compatible = "xlnx,zynq-usb-2.20a", "chipidea,usb2";
	status = "disabled";
	clocks = <&clkc 28>;
	interrupt-parent = <&intc>;
	interrupts = <0 21 4>;
	reg = <0xe0002000 0x1000>;
	phy_type = "ulpi";
};

&usb0 {
	status = "okay";

	dr_mode = "host";
	usb-phy = <&usb_phy0>;
};

So when that patch copies the DT node to the new platform device
in ci_hdrc_add_device it copies the compatible stuff as well as
the IRQ stuff it was targeting, this presumably causes the kernel
to bind a new copy of the driver to that new device, which probes
and calls ci_hdrc_add_device again repeating the process until
it dies.

Kinda looks to me like the best solution might just be to revert
the patch, I am not sure I see how that copy of the DT is supposed
to work?

Thanks,
Charles