From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752375AbcFFCpm (ORCPT ); Sun, 5 Jun 2016 22:45:42 -0400 Received: from mga01.intel.com ([192.55.52.88]:34777 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752010AbcFFCpk (ORCPT ); Sun, 5 Jun 2016 22:45:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,424,1459839600"; d="scan'208";a="991673083" Subject: Re: [PATCH v10 2/7] usb: mux: add generic code for dual role port mux To: Peter Chen References: <1464831449-8973-1-git-send-email-baolu.lu@linux.intel.com> <1464831449-8973-3-git-send-email-baolu.lu@linux.intel.com> <20160603074113.GA30006@shlinux2> <5751AAEE.2090001@linux.intel.com> <20160604022838.GA26936@shlinux2> <5753CCFC.2060504@linux.intel.com> <5753E6FF.5010501@linux.intel.com> <20160606020507.GB16012@shlinux2> Cc: Jun Li , "felipe.balbi@linux.intel.com" , Mathias Nyman , Greg Kroah-Hartman , Lee Jones , Heikki Krogerus , Liam Girdwood , Mark Brown , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Roger Quadros From: Lu Baolu Message-ID: <5754E3CE.8030706@linux.intel.com> Date: Mon, 6 Jun 2016 10:45:34 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20160606020507.GB16012@shlinux2> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On 06/06/2016 10:05 AM, Peter Chen wrote: > On Sun, Jun 05, 2016 at 04:46:55PM +0800, Lu Baolu wrote: >> Hi, >> >> On 06/05/2016 04:33 PM, Jun Li wrote: >>>> Port mux is part of dual role switch, but not the whole thing. >>>>> Dual role switch includes at least below things: >>>>> - ID or type-C event detection >>>>> - port mux >>>>> - VBUS management >>>>> - start/stop host/device controllers >>>>> >>>>> An OTG/Dual-role framework can be used to keep all these things run >>>>> together with an internal state machine. But it's not duplicated with a >>>>> generic framework for port mux and the port mux drivers. >>>>> >>>>>>> Your >>>>>>> case is just like Renesas case, which uses two different drivers >>>>>>> between peripheral and host[1]. >>>>> In my case, the port mux devices are physical devices and they can be >>>>> controlled through GPIO pins or device registers. They are independent of >>>>> both peripheral and host controllers. >>>>> >>> I also think current OTG/Dual role framework can support your case, if you >>> find there is any limitation of it which can't meet your requirement, we >>> should improve it, Roger also provide an example of dual role switch with >>> USB3 based on his OTG core. >> Why do we need an OTG framework to support a device driver? > Just like you said above, OTG framework can manage role switch, the > role switch may need to start or stop host/gadget driver according to > different hardware signals or user input. We don't have any OTG or dual-role (reduced OTG) capable controllers. So we don't need to aid OTG framework to start/stop host/gadget drivers. > >> Is it something like a bus or class driver? > The DRD/OTG framework uses the same device structure with the caller, > the caller can be a dual-role controller driver (like dwc3, chipidea, > etc), or a separate switch driver which like your mux port driver. > >>From my point of view, this isn't the right way to handle a port mux device. We have many kinds of port mux devices across multiple archs, we should have a generic framework for them, so that consumers, (like OTG framework) can manipulate port mux devices through a common interfaces. Just like we already have frameworks for PHY, VBUS regulator and ... Best regards, Lu Baolu