Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755741AbcKKLC5 (ORCPT ); Fri, 11 Nov 2016 06:02:57 -0500 Received: from mga02.intel.com ([134.134.136.20]:58058 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752576AbcKKLCz (ORCPT ); Fri, 11 Nov 2016 06:02:55 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.31,621,1473145200"; d="scan'208";a="1067136965" Date: Fri, 11 Nov 2016 13:02:48 +0200 From: Heikki Krogerus To: Stephen Boyd Cc: linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Andy Gross , Bjorn Andersson , Neil Armstrong , Arnd Bergmann , Felipe Balbi , Peter Chen , Greg Kroah-Hartman , devicetree@vger.kernel.org, Rob Herring Subject: Re: [PATCH v5 03/23] usb: ulpi: Support device discovery via DT Message-ID: <20161111110248.GA22706@kuha.fi.intel.com> References: <20161018015636.11701-1-stephen.boyd@linaro.org> <20161018015636.11701-4-stephen.boyd@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161018015636.11701-4-stephen.boyd@linaro.org> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1861 Lines: 40 On Mon, Oct 17, 2016 at 06:56:16PM -0700, Stephen Boyd wrote: > The qcom HSIC ULPI phy doesn't have any bits set in the vendor or > product ID registers. This makes it impossible to make a ULPI > driver match against the ID registers. Add support to discover > the ULPI phys via DT help alleviate this problem. In the DT case, > we'll look for a ULPI bus node underneath the device registering > the ULPI viewport (or the parent of that device to support > chipidea's device layout) and then match up the phy node > underneath that with the ULPI device that's created. > > The side benefit of this is that we can use standard properties > in the phy node like clks, regulators, gpios, etc. because we > don't have firmware like ACPI to turn these things on for us. And > we can use the DT phy binding to point our phy consumer to the > phy provider. > > The ULPI bus code supports native enumeration by reading the > vendor ID and product ID registers at device creation time, but > we can't be certain that those register reads will succeed if the > phy is not powered up. To avoid any problems with reading the ID > registers before the phy is powered we fallback to DT matching > when the ID reads fail. > > If the ULPI spec had some generic power sequencing for these > registers we could put that into the ULPI bus layer and power up > the device before reading the ID registers. Unfortunately this > doesn't exist and the power sequence is usually device specific. > By having the device matched up with DT we can avoid this > problem. > > Cc: Greg Kroah-Hartman > Cc: Heikki Krogerus > Cc: > Cc: Rob Herring > Signed-off-by: Stephen Boyd Acked-by: Heikki Krogerus -- heikki