From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750852AbdALOvy (ORCPT ); Thu, 12 Jan 2017 09:51:54 -0500 Received: from fllnx209.ext.ti.com ([198.47.19.16]:25641 "EHLO fllnx209.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750742AbdALOvw (ORCPT ); Thu, 12 Jan 2017 09:51:52 -0500 Date: Thu, 12 Jan 2017 08:50:14 -0600 From: Bin Liu To: Maxime Ripard CC: Icenowy Zheng , Chen-Yu Tsai , Kishon Vijay Abraham I , "devicetree@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-usb@vger.kernel.org" Subject: Re: [PATCH 4/4] ARM: dts: sun8i: add OTG function to Lichee Pi Zero Message-ID: <20170112145014.GC16865@uda0271908> Mail-Followup-To: Bin Liu , Maxime Ripard , Icenowy Zheng , Chen-Yu Tsai , Kishon Vijay Abraham I , "devicetree@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-usb@vger.kernel.org" References: <20170103152534.20118-1-icenowy@aosc.xyz> <20170103152534.20118-5-icenowy@aosc.xyz> <20170110202443.GC2479@uda0271908> <2733831484164533@web1g.yandex.ru> <20170111200811.GA16865@uda0271908> <20170111210638.ppdnpzdd2l6x4lyo@lukather> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170111210638.ppdnpzdd2l6x4lyo@lukather> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 11, 2017 at 10:06:38PM +0100, Maxime Ripard wrote: > On Wed, Jan 11, 2017 at 02:08:11PM -0600, Bin Liu wrote: > > On Thu, Jan 12, 2017 at 03:55:33AM +0800, Icenowy Zheng wrote: > > > > > > > > > 11.01.2017, 04:24, "Bin Liu" : > > > > On Tue, Jan 03, 2017 at 11:25:34PM +0800, Icenowy Zheng wrote: > > > >>  Lichee Pi Zero features a USB OTG port. > > > >> > > > >>  Add support for it. > > > >> > > > >>  Note: in order to use the Host mode, the board must be powered via the > > > >>  +5V and GND pins. > > > >> > > > >>  Signed-off-by: Icenowy Zheng > > > >>  --- > > > >>   arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts | 10 ++++++++++ > > > >>   1 file changed, 10 insertions(+) > > > >> > > > >>  diff --git a/arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts b/arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts > > > >>  index 0099affc6ce3..3d9168cbaeca 100644 > > > >>  --- a/arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts > > > >>  +++ b/arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts > > > >>  @@ -71,3 +71,13 @@ > > > >>           pinctrl-names = "default"; > > > >>           status = "okay"; > > > >>   }; > > > >>  + > > > >>  +&usb_otg { > > > >>  + dr_mode = "otg"; > > > > > > > > Why not set this default mode in dtsi instead? > > > > > > > > Regards, > > > > -Bin. > > > > > > There's possibly boards which do not have OTG functions. > > > > That is board specific. > > Exactly, and this is why it should be done in the board DT. I am just suggesting based on the common practice. If a .dtsi exists for a family, the .dtsi describes the device and common properties for all possible boards, and each board .dts adds or overrides its specific implementation. Kernel has many devices/boards done in this way - define the default dr_mode in .dtsi. In this case, I suggest to set the common dr_mode in .dtsi, then each board .dts only overrides it if the implementation is different. > > The controller in the Allwinner SoCs do not handle directly the ID pin > and VBUS, but rather rely on a GPIO to do so. > > So boards with OTG will need setup anyway, at least to tell which > GPIOs are used. There's no point in enforcing a default if it doesn't > work by default. Then define a default which supposes to work for most boards. Why I suggest this, is because defining a default dr_mode which works for most cases in dtsi could prevent a little surprise in MUSB function. If someone designs a new board but forgets to define dr_mode in the new board DT, the MUSB driver will default to org mode, which might not be intended. Regards, -Bin.