From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C3D60C432BE for ; Mon, 23 Aug 2021 14:00:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7EFA613A5 for ; Mon, 23 Aug 2021 14:00:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229882AbhHWOBg (ORCPT ); Mon, 23 Aug 2021 10:01:36 -0400 Received: from netrider.rowland.org ([192.131.102.5]:36721 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S229755AbhHWOBg (ORCPT ); Mon, 23 Aug 2021 10:01:36 -0400 Received: (qmail 121444 invoked by uid 1000); 23 Aug 2021 10:00:52 -0400 Date: Mon, 23 Aug 2021 10:00:52 -0400 From: Alan Stern To: Alexander Dahl Cc: linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, rca@thorsis.com Subject: Re: Enable HSIC Host Port on Atmel/Microchip SAMA5D2 Message-ID: <20210823140052.GA120849@rowland.harvard.edu> References: <2869763.XZdSvA6Ref@ada> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2869763.XZdSvA6Ref@ada> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 23, 2021 at 11:24:35AM +0200, Alexander Dahl wrote: > Hello, > > for a new embedded board featuring a Microchip SAMA5D2 SoC (64 MiB SiP variant > SAMA5D27C-D5M) we connected the third USB host port (HSIC only) with an > USB3503 hub chip. This doesn't work out of the box with the Linux kernel > currently, because neither the SoC nor the kernel does enable the HSIC > interface by default. > > That SoC has three USB host ports, from the SAMA5D2 Series Datasheet [1] I > learned there's a flag in an EHCI register, which has to be set to enable the > HSIC interface on port C, the third port. (Section "41.7.14 EHCI: REG08 - HSIC > Enable/Disable" of the datasheet.) I suppose that register is vendor specific. > The register definitions in '/include/linux/usb/ehci_def.h' do not contain > that register. > > Where would I add that register definition and set that flag in the kernel > then? I suppose in the vendor specific ehci driver? > That would be 'drivers/usb/host/ehci-atmel.c' right? That is where you would set the flag. You might want to put the register definition in ehci_def.h, with the other definitions. > Since that feature is optional (other boards don't need to turn on hsic on > that port), some driver specific new device tree binding would be necessary, > right? I suppose that would have to be documented in 'Documentation/ > devicetree/bindings/usb/atmel-usb.txt' right? (Or that would have to be > converted to yaml first?) Yes, it would have to go into the device tree data somehow. I don't know the best way to do this; people who know more about DT may be able to tell you. > Is this the right track? If yes, I'm going to develop patches for this. > Otherwise any hint into the right direction are highly appreciated. Yes, this is the right approach. Alan Stern > FWIW, I'm not the first one struggling [2] with this problem. ;-) > > Greets > Alex > > [1] https://www.microchip.com/en-us/product/ATSAMA5D27C-D5M#document-table > [2] https://community.atmel.com/forum/sama5d2-using-hsic-under-linux