From: Alan Stern <stern@rowland.harvard.edu>
To: John Stultz <john.stultz@linaro.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
Chen Yu <chenyu56@huawei.com>, Wei Xu <xuwei5@hisilicon.com>,
Guodong Xu <guodong.xu@linaro.org>,
Amit Pundir <amit.pundir@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
John Youn <johnyoun@synopsys.com>,
Douglas Anderson <dianders@chromium.org>,
Kishon Vijay Abraham I <kishon@ti.com>,
Felipe Balbi <felipe.balbi@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
<linux-usb@vger.kernel.org>
Subject: Re: [RFC][PATCH 5/5] usb: dwc2: Add a quirk to allow speed negotiation for Hisilicon Hi6220
Date: Tue, 13 Dec 2016 08:24:08 -0500 (EST) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1612130822320.31292-100000@netrider.rowland.org> (raw)
In-Reply-To: <1481612990-23409-6-git-send-email-john.stultz@linaro.org>
On Mon, 12 Dec 2016, John Stultz wrote:
> From: Chen Yu <chenyu56@huawei.com>
>
> The Hi6220's usb controller is limited in that it does not
> support "Split Transactions", so it does not support communicating
> with low-speed and full-speed devices behind a high-speed hub.
>
> Thus it requires a quirk so that we can manually drop the usb
> speed when low/full-speed are attached, and bump back to high
> speed when they are removed.
Just out of curiosity (I know nothing about this hardware), what
happens if there is a high-speed hub plugged into the host controller
and both a high-speed and a full-speed device plugged into the hub?
Do you end up forcing the high-speed device to run at full speed?
Alan Stern
next prev parent reply other threads:[~2016-12-13 13:24 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-13 7:09 [RFC][PATCH 0/5] Fixes and workarounds for dwc2 on HiKey board John Stultz
2016-12-13 7:09 ` [RFC][PATCH 1/5] usb: dwc2: Avoid sleeping while holding hsotg->lock John Stultz
2016-12-13 7:09 ` [RFC][PATCH 2/5] usb: dwc2: Workaround case where GOTGCTL state is wrong John Stultz
2016-12-13 12:28 ` Vardan Mikayelyan
2016-12-13 20:40 ` John Stultz
2016-12-13 7:09 ` [RFC][PATCH 3/5] usb: dwc2: Force port resume on switching to device mode John Stultz
2016-12-13 7:09 ` [RFC][PATCH 4/5] usb: dwc2: Avoid suspending if we're in gadget mode John Stultz
2016-12-13 7:09 ` [RFC][PATCH 5/5] usb: dwc2: Add a quirk to allow speed negotiation for Hisilicon Hi6220 John Stultz
2016-12-13 13:24 ` Alan Stern [this message]
2016-12-13 19:23 ` John Stultz
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