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

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Message-ID: <3544eb61-2bd8-338d-8d62-d95a775528ef@samsung.com>
Date:   Mon, 13 May 2019 11:07:56 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Peter Chen <peter.chen@....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

Hi Peter,

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?

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland