Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751269AbdCHOpV (ORCPT ); Wed, 8 Mar 2017 09:45:21 -0500 Received: from bh-25.webhostbox.net ([208.91.199.152]:36852 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750778AbdCHOpR (ORCPT ); Wed, 8 Mar 2017 09:45:17 -0500 Subject: Re: [PATCH v17 2/3] usb: USB Type-C connector class To: Peter Chen , Heikki Krogerus References: <20170221142405.76299-1-heikki.krogerus@linux.intel.com> <20170221142405.76299-3-heikki.krogerus@linux.intel.com> <20170303033529.GA18650@b29397-desktop> <20170303143133.GB6999@kuha.fi.intel.com> <20170306011551.GA23305@b29397-desktop> <20170306131619.GD6999@kuha.fi.intel.com> <20170307085753.GF6999@kuha.fi.intel.com> Cc: Peter Chen , Greg KH , Felipe Balbi , Oliver Neukum , "linux-kernel@vger.kernel.org" , "linux-usb@vger.kernel.org" , Roger Quadros , Jun Li From: Guenter Roeck Message-ID: <055d6289-c728-30bb-279e-65e08be5e538@roeck-us.net> Date: Wed, 8 Mar 2017 06:44:47 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3014 Lines: 63 On 03/07/2017 10:50 PM, Peter Chen wrote: > >>>> You mean type-C trigger an ACPI event, and this ACPI event can notify >>>> related USB controller driver doing role switch? >>> >>> No (firmware programs the dual-role hw/registers), but never mind. >>> That could be the case. >>> >>>> If it is correct, there is a notifier between type-C and USB >>>> controller driver, how to define this notifier for non-ACPI platform? >>> >>> Once there is a platform with Type-C like that, the problem needs to >>> be solved. However.. >>> >>>>> I'm not commenting on Roger's dual role patch series, but I don't >>>>> really think it should be mixed with Type-C. USB Type-C and USB >>>>> Power Delivery define their own ways of handling the roles, and they >>>>> are not limited to the data role only. Things like OTG for example >>>>> will, and actually can not be supported. With Type-C we will have >>>>> competing state machines compared to OTG. The dual-role framework >>>>> may be useful on systems that provide more traditional connectors, >>>>> which possibly have the ID-pin like micro-AB, and possibly also >>>>> support OTG. It can also be something that exist in parallel with the Type-C >> class, but there just can not be any dependencies between the two. >>>>> >>>> >>>> Yes, there are two independent things. But if the kernel doesn't have >>>> a notifier between type-C message sender (type-c class) and message >>>> receiver (like USB controller driver for role switch or other drivers >>>> for alternate mode message), we had to find some ways at userspace. >>> >>> ..what ever the solution is, it really can't rely on user space. >>> >> >> ... and, at least for our application, using extcon for the necessary notifications works >> just fine. >> > > I see, that means you have a hardware signal to notify role switch. > In our case the Type-C protocol manager (including alternate mode handling) is implemented in an EC. The EC signals the extcon-cros_ec driver, which in turn signals the phy driver as well as the DP driver. The Type-C class is orthogonal; extcon-cros_ec will also register with the Type-C class code once that is upstream. As mentioned earlier, using extcon for signaling was the most convenient means for us to pass events around. I am more than open to change it to a bus, if that can be made to work - we'd have to keep in mind though that this code already works without Type-C infrastructure and is for the most part already upstream (the rk3399 code it ties into is upstream, and extcon-cros_ec has been submitted as https://patchwork.kernel.org/patch/9583045/). As for to how to handle alternate mode if the Type-C protocol manager (TCPM) is implemented in the kernel - I have not yet implemented it yet, but my thinking goes along the line described by Heikki in his last e-mail. Note that we also have a kernel driver for FUSB302 which ties into my tcpm driver. I'll have to check if that is public yet and if I or someone else can publish it if there is interest. Guenter