Re: [PATCH v2 0/3] USB: add generic onboard USB HUB driver

From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
To: Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org>,
	Shawn Guo <shawnguo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Greg Kroah-Hartman
	<gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>,
	Alan Stern
	<stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org>,
	"linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org"
	<linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>,
	"kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org"
	<kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>,
	"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>,
	Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
	Fabio Estevam <festevam-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Philipp Zabel <p.zabel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>,
	patryk-6+2coLtxvIyvnle+31E0rA@public.gmane.org,
	Linux USB List
	<linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Felipe Balbi <balbi-l0cyMroinI0@public.gmane.org>,
	Mathieu Poirier
	<mathieu.poirier-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH v2 0/3] USB: add generic onboard USB HUB driver
Date: Thu, 17 Dec 2015 00:13:07 +0100	[thread overview]
Message-ID: <1827708.e1pfN6rEID@wuerfel> (raw)
In-Reply-To: <CAL_Jsq+KAF6FGyOyC0JzODsSVoK4+V6umpj=cANywgui_wOKMg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Wednesday 16 December 2015 16:59:39 Rob Herring wrote:
> On Mon, Dec 14, 2015 at 3:35 AM, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
> > On Monday 14 December 2015 15:26:11 Peter Chen wrote:
>
> I agree on doing it properly, but am not sure that pwrseq binding for
> MMC is proper. The pwrseq binding is fairly limited and working around
> the driver model IMO. Hubs may also need I2C setup which I don't think
> could be done generically other than some defined sequence of i2c
> transactions. The current project I'm working on needs to use I2C to
> configure the hub to use HSIC mode for example. I really think we need
> a pre-probe driver hook to handle this. That would allow device
> specific setup to live in the driver.
> 
> Perhaps a more simple approach would be just forcing driver probe if a
> DT node is present. I'm not all that familiar with USB drivers, but
> presumably there is some setup before probe like setting the USB
> device address. We'd have to allow doing that later during probe.

Yes, good idea. I was also advocating that approach for MMC at some
point, but the power sequencing made it in the end.

	Arnd
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