From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Chen Subject: Re: [PATCH 1/3] usb: misc: generic_onboard_hub: add generic onboard USB HUB driver Date: Wed, 9 Dec 2015 17:00:00 +0800 Message-ID: <20151209085959.GG941@shlinux2> References: <1449538670-7954-1-git-send-email-peter.chen@freescale.com> <1449538670-7954-2-git-send-email-peter.chen@freescale.com> <20151209085021.GF941@shlinux2> <1449651460.3118.22.camel@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Content-Disposition: inline In-Reply-To: <1449651460.3118.22.camel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Lucas Stach Cc: Mathieu Poirier , Mark Rutland , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , festevam-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, Philipp Zabel , =?utf-8?B?UGF3ZcWC?= Moll , Greg KH , linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, patryk-6+2coLtxvIyvnle+31E0rA@public.gmane.org, Rob Herring , stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org, kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, Shawn Guo , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: devicetree@vger.kernel.org On Wed, Dec 09, 2015 at 09:57:40AM +0100, Lucas Stach wrote: > Am Mittwoch, den 09.12.2015, 16:50 +0800 schrieb Peter Chen: > > On Tue, Dec 08, 2015 at 08:36:00AM -0700, Mathieu Poirier wrote: > > > On 7 December 2015 at 18:37, Peter Chen wrote: > > > > + > > > > + if (dev->of_node) { > > > > + struct device_node *node = dev->of_node; > > > > + > > > > + hub_data->clk = devm_clk_get(dev, "external_clk"); > > > > + if (IS_ERR(hub_data->clk)) { > > > > + dev_dbg(dev, "Can't get external clock: %ld\n", > > > > + PTR_ERR(hub_data->clk)); > > > > + } > > > > > > Is the intended behaviour to keep going here event when there is an > > > error? Can the "hub_data" really work without a clock? > > > > Yes, some HUB may work with fixed 24M OSC at the board, but they need to > > reset through external IO, so the clock is not need at this case, but > > reset pin is mandatory. > > > If the hub always requires a clock it must not be optional. If you have > a fixed 24MHz clock on board add this to the DT as a fixed-clock and use > it as an input to the hub. > This fixed 24MHz clock may from a fixed crystal on board, it is always on, no software need to control it, imx51-bbg board is an example. -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html