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Date:   Fri, 10 Aug 2018 10:19:30 -0400 (EDT)
From:   Alan Stern <stern@rowland.harvard.edu>
To:     Roger Quadros <rogerq@ti.com>
cc:     Zeng Tao <prime.zeng@hisilicon.com>, <gregkh@linuxfoundation.org>,
        <mathias.nyman@linux.intel.com>, <drinkcat@chromium.org>,
        <felipe.balbi@linux.intel.com>, <drake@endlessm.com>,
        <mike.looijmans@topic.nl>, <joe@perches.com>,
        <linux-usb@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] usb: hub: try old enumeration scheme first for high
 speed devices
In-Reply-To: <a29afa26-22b4-3188-f9ee-993e44df7703@ti.com>
Message-ID: <Pine.LNX.4.44L0.1808101017050.1425-100000@iolanthe.rowland.org>
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On Fri, 10 Aug 2018, Roger Quadros wrote:

> Hi,
> 
> On 10/08/18 18:01, Zeng Tao wrote:
> > The new scheme is required just to support legacy low and full-speed
> > devices. For high speed devices, it will slower the enumeration speed.
> > So in this patch we try the "old" enumeration scheme first for high speed
> > devices.
> 
> How slow does it get? Is it significant?
> Do we risk breaking existing HS devices that work? I don't think we can
> be sure till we run this through testing.

Indeed.  I am extremely skeptical about a patch like this, unless
somebody can show that Windows uses the "old" scheme for high-speed 
devices.

Alan Stern