linux-kernel - RE: [PATCH v3] usb: core: verify devicetree nodes for USB devices

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Date:   Mon, 13 May 2019 09:23:24 +0000
From:   Peter Chen <peter.chen@....com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Måns Rullgård <mans@...sr.com>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Markus Reichl <m.reichl@...etechno.de>,
        Krzysztof Kozlowski <krzk@...nel.org>
Subject: RE: [PATCH v3] usb: core: verify devicetree nodes for USB devices

 
> On 2019-05-13 11:00, Peter Chen wrote:
> >> On 2019-05-10 05:10, Peter Chen wrote:
> >>>> Marek Szyprowski <m.szyprowski@...sung.com> writes:
> >>>>> Commit 69bec7259853 ("USB: core: let USB device know device node")
> >>>>> added support for attaching devicetree node for USB devices. The
> >>>>> mentioned commit however identifies the given USB device node only
> >>>>> by the
> >> 'reg'
> >>>>> property in the host controller children nodes. The USB device
> >>>>> node however also has to have a 'compatible' property as described
> >>>>> in Documentation/devicetree/bindings/usb/usb-device.txt. Lack for
> >>>>> the 'compatible' property check might result in assigning a
> >>>>> devicetree node, which is not intended to be the proper node for the given
> USB device.
> >>>>>
> >>>>> This is important especially when USB host controller has
> >>>>> child-nodes for other purposes. For example, Exynos EHCI and OHCI
> >>>>> drivers already define child-nodes for each physical root hub port
> >>>>> and assigns respective PHY controller and parameters for them.
> >>>>> Those binding predates support for USB devicetree nodes.
> >>>>>
> >>>>> Checking for the proper compatibility string allows to mitigate
> >>>>> the conflict between USB device devicetree nodes and the bindings
> >>>>> for USB controllers with child nodes. It also fixes the
> >>>>> side-effect of the other commits, like 01fdf179f4b0 ("usb: core:
> >>>>> skip interfaces disabled in devicetree"), which incorrectly
> >>>>> disables some devices on Exynos based boards.
> >>> Hi Marek,
> >>>
> >>> The purpose of your patch is do not set of_node for device under USB
> >>> controller,
> >> right?
> >>
> >> Right.
> >>
> > Do you mind doing it at function exynos_ehci_get_phy of ehci-exynos.c?
> 
> I don't mind fixing it in ehci-exynos, but frankly so far I have no idea how to do it.
> The problem is that newly created USB devices get of-node pointer pointing to a
> node which if not intended for them. How this can be fixed in ehci-exynos?
> 
 
Can't be workaround by setting of_node as NULL for EHCI controller or for PHY node at
exynos_ehci_get_phy?

Peter