From: Alan Stern <stern@rowland.harvard.edu>
To: Claus Stovgaard <claus.stovgaard@gmail.com>
Cc: "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: Re: Options for forcing dwc3 gadget to only accept superspeed
Date: Tue, 12 May 2020 15:52:31 -0400 [thread overview]
Message-ID: <20200512195231.GA26080@rowland.harvard.edu> (raw)
In-Reply-To: <8943a225c6d8354f2f5fe0ea7270dc0fa1293180.camel@gmail.com>
On Tue, May 12, 2020 at 09:25:38PM +0200, Claus Stovgaard wrote:
> Hi all
>
> I have a system, using a Xilinx ZynqMP with kernel 4.19, using the
> build in dwc3 core as a USB device. (It is a custom device using
> ConfigFS / FunctionFS).
>
> In a certain scenario I would like to force the dwc3 to only connect
> via superspeed and not fall back to USB2.
>
> What options exist for forcing the dwc3 to keep retry?
The USB-3 spec forbids devices from operating only at SuperSpeed.
Devices must be able to connect at high speed, although possibly with
reduced functionality.
Alan Stern
> I know about the U2RSTECN from GCTL -
> https://www.xilinx.com/html_docs/registers/ug1087/usb3_xhci___gctl.html
>
> So was wondering if other options existed, where I can force it to
> continue try to connect as SuperSpeed.
>
> Or if it is possible to setup the high speed descriptors for ffs, so
> the host automatically will reset the bus / device so it newer will be
> reported as connected, unless it is with super speed.
next prev parent reply other threads:[~2020-05-12 19:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-12 19:25 Options for forcing dwc3 gadget to only accept superspeed Claus Stovgaard
2020-05-12 19:52 ` Alan Stern [this message]
2020-05-12 20:08 ` Claus Stovgaard
2020-05-13 4:43 ` Sid Spry
2020-05-13 4:47 ` Sid Spry
2020-05-14 7:06 ` Claus Stovgaard
2020-05-13 7:34 ` Felipe Balbi
2020-05-14 8:53 ` Claus Stovgaard
2020-05-14 9:34 ` Felipe Balbi
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