linux-kernel - Re: [RFT PATCH 1/3] usb: misc: usb3503: Fix HUB mode after bootloader initialization

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Date:	Tue, 3 May 2016 13:00:22 -0500
From:	Rob Herring <robh@...nel.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Kukjin Kim <kgene@...nel.org>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-usb@...r.kernel.org,
	linux.amoon@...il.com, tjakobi@...h.uni-bielefeld.de,
	m.szyprowski@...sung.com, hverkuil@...all.nl,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [RFT PATCH 1/3] usb: misc: usb3503: Fix HUB mode after
 bootloader initialization

On Mon, May 02, 2016 at 11:55:01AM +0100, Mark Brown wrote:
> On Mon, May 02, 2016 at 11:49:12AM +0200, Krzysztof Kozlowski wrote:
> 
> > This VDD regulator supply actually is not a usb3503 USB HUB regulator
> > supply... but a supply to the LAN attached to this HUB. Regulator off/on
> > is needed for LAN to show up. The hub will show up with typical reset
> > (which is also missing before my patchset btw).
> 
> > The LAN, as a USB device, is auto-probed so it cannot take the regulator
> > and play with it. The simplest idea I have is to add it as "external
> > supply"  to the parent: usb3503.
> 
> This is common enough that that just isn't going to scale well I fear
> without some generic handling, either walking child devices at the bus
> level or at the device level with a pre-probe() callback to get the
> device to power on.  The latter is more appropriate to things like
> Slimbus where the device is more likely to do active management at
> runtime, it's not clear people are building USB devices like that.

There's a new binding and support in -next (.../usb/usb-device.txt) for 
USB devices that should help here. Though, how to handle a hub on USB 
and I2C buses would need to be worked out.

Rob