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

From: Marek Szyprowski
Date: Mon May 13 2019 - 06:04:56 EST

Hi Peter,

On 2019-05-13 11:23, Peter Chen wrote:
>> On 2019-05-13 11:00, Peter Chen wrote:
>>>> On 2019-05-10 05:10, Peter Chen wrote:
>>>>>> Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> 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?

Ah, such workaround? I will check, but this will need to be done with
care, because have a side effect for other subsystems like regulators or

BTW, What's wrong with proper, full verification of USB device nodes?

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