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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46A20C433EF for ; Mon, 23 May 2022 13:10:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235935AbiEWNKg (ORCPT ); Mon, 23 May 2022 09:10:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56206 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235923AbiEWNK3 (ORCPT ); Mon, 23 May 2022 09:10:29 -0400 Received: from relay-us1.mymailcheap.com (relay-us1.mymailcheap.com [51.81.35.219]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4763454185; Mon, 23 May 2022 06:10:27 -0700 (PDT) Received: from relay5.mymailcheap.com (relay5.mymailcheap.com [159.100.241.64]) by relay-us1.mymailcheap.com (Postfix) with ESMTPS id 23A0520158; Mon, 23 May 2022 13:10:26 +0000 (UTC) Received: from relay1.mymailcheap.com (relay1.mymailcheap.com [149.56.97.132]) by relay5.mymailcheap.com (Postfix) with ESMTPS id 9A1CA200FE; Mon, 23 May 2022 13:10:22 +0000 (UTC) Received: from filter1.mymailcheap.com (filter1.mymailcheap.com [149.56.130.247]) by relay1.mymailcheap.com (Postfix) with ESMTPS id 8D02A3F203; Mon, 23 May 2022 13:10:20 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by filter1.mymailcheap.com (Postfix) with ESMTP id 81A6F2A384; Mon, 23 May 2022 13:10:20 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at filter1.mymailcheap.com Received: from filter1.mymailcheap.com ([127.0.0.1]) by localhost (filter1.mymailcheap.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xRHO4Msw78f3; Mon, 23 May 2022 13:10:19 +0000 (UTC) Received: from mail20.mymailcheap.com (mail20.mymailcheap.com [51.83.111.147]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by filter1.mymailcheap.com (Postfix) with ESMTPS; Mon, 23 May 2022 13:10:19 +0000 (UTC) Received: from edelgard.icenowy.me (unknown [59.41.161.142]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail20.mymailcheap.com (Postfix) with ESMTPSA id 0A57A4010C; Mon, 23 May 2022 13:10:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=aosc.io; s=default; t=1653311418; bh=tCctaG9lD2zZr9aAnMweZ8VtB5FmvJDDCVIR2dwhiCs=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=tRLM43pIC2yfKKJHo3qlEzTagk6+uyxU63u5TDAZSqr8UH0/qUAC6YkzqLh4l3Vbl OPF42qDhNsnkbu02SqvDqdxFTzKSlvyvGcxO64mHyt2vhuwu9uebOiqfC+Jtknf3M9 jSZP+HgNm5aa3QPBl25NebIs2VAsIB0njuwI+o3s= Message-ID: <265770e7055837fee26a7a66ce1fcbc7989eaf99.camel@aosc.io> Subject: Re: [PATCH v4 0/2] ARM: sun8i-r40: Enable usb otg support From: Icenowy Zheng To: Evgeny Boger , qianfanguijin@163.com Cc: andre.przywara@arm.com, devicetree@vger.kernel.org, jernej.skrabec@gmail.com, krzysztof.kozlowski+dt@linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-sunxi@lists.linux.dev, robh+dt@kernel.org, samuel@sholland.org, wens@csie.org Date: Mon, 23 May 2022 21:10:09 +0800 In-Reply-To: References: <264cb004-677a-13df-cc68-676ef3c2e7d8@163.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.40.4 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 在 2022-05-19星期四的 23:54 +0300，Evgeny Boger写道： > Hi qianfan, > > As Allwinner A40i user, let me first thank you for your effort for > making better upstream support for R40! > > However, I would strongly suggest *not* to add USB support to one > more > Allwinner SoC in this particular way. > The problem is, this approach consists of a number of carefully > crafted > hacks in device tree to make current drivers work on Allwinner > hardware > without modification to the drivers. > > a few examples: > > 1) please notice how ohci0 and ehci0 nodes do not contain reference > to > usb phy. It is done intentionally, otherwise EHCI will reset musb > mode. > Of course omitting phy reference here is also completely breaking > power > cycling in case of usb error and otherwise messes with a power > management. > > 2) one must always enable ohci, ehci and usb_otg nodes at the same > time. > If one forgets to enable ohci/ehci nodes while enabling usb_otg node, > the system will silently fail to work as USB host. > > 3) For host-only mode we still have to enable usb_otg node despite no > role switching is needed. That's because phy reference is missing in > ehci/ohci, so the ehci/ohci driver won't enable the PHY. > Also I might be wrong, but I think phy won't be routed to ehci/ohci > controllers is this case. > > 4) musb host controller is initialized and present to hardware though > never actually used > > To summarize, not only the resulting device tree is not describing > the > hardware properly, it is creating device tree configuration which > will > be very hard to support in future, once proper driver support is in > place. > > > At Wiren Board kernel tree we tried to untangle this issue [1-6]. > Unfortunately I didn't have time to prepare it for kernel submission > yet, but I think I better submit it as RFC to get a feedback from you > and others. Please cc me in the following patches because it's me who makes the whole dual route thing hacky. > > > [1] > https://github.com/wirenboard/linux/commit/359abbbd86ddff4d3c61179c882c286de32bb089 > [2] > https://github.com/wirenboard/linux/commit/6327f9d7972c21b229fb83457fdde643b31553f9 > [3] > https://github.com/wirenboard/linux/commit/f01f4c66758bde460a4d8c5b54ecee3b585c0232 > [4] > https://github.com/wirenboard/linux/commit/c27598ad601e5a46f624b73412a531d6f1f63d37 > [5] > https://github.com/wirenboard/linux/commit/5796d6eebb86b32a3751b2038b63af46f94954b3 > [6] > https://github.com/wirenboard/linux/commit/0928a675d875f9c2849fd3a9888f718bbb673bda > >