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

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Message-ID: <20210304013548.GA16596@nchen>
Date:   Thu, 4 Mar 2021 09:35:49 +0800
From:   Peter Chen <peter.chen@...nel.org>
To:     liulongfang <liulongfang@...wei.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, mathias.nyman@...el.com,
        linux-usb@...r.kernel.org, yisen.zhuang@...wei.com,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] USB:XHCI:Modify XHCI driver for USB2.0 controller

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?

-- 

Thanks,
Peter Chen