Re: [RFC PATCH] USB:XHCI:Modify XHCI driver for USB2.0 controller

liulongfang
2021-03-04T04:10:31Z

On 2021/3/4 9:35, Peter Chen wrote:
> On 21-02-27 11:31:00, liulongfang wrote:
>> On 2021/2/26 16:38, Greg KH wrote:
>>> On Fri, Feb 26, 2021 at 04:21:37PM +0800, Longfang Liu wrote:
>>>> Our current XHCI hardware controller has been customized to only
>>>> support USB 2.0 ports.
>>>
>>> That sounds like a spec violation, right? Why do you want to do this?
>>>
>>> greg k-h
>>> .
>>>
>> I hope to support a USB2.0-only mode on the XHCI controller
>> through software configuration.
>> Thanks.
>
> If your hardware has disabled USB3 logic, when the USB3 device is plugged,
> since there are no RX signal on the bus, the device will not enable USB3
> logic, and only USB2 signals will be on the bus, there are only USB devices on
> USB2 roothub later. So, any issues you have met?
>
I don’t want to see the USB3 bus controller in the system,
but it actually exists.
Thanks.
Longfang, Liu