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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E923CC43332 for ; Wed, 3 Mar 2021 20:55:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B2BBC64EF8 for ; Wed, 3 Mar 2021 20:55:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1386606AbhCCSop convert rfc822-to-8bit (ORCPT ); Wed, 3 Mar 2021 13:44:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59776 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346408AbhCCQ0P (ORCPT ); Wed, 3 Mar 2021 11:26:15 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 097CDC061763 for ; Wed, 3 Mar 2021 08:25:25 -0800 (PST) Received: from lupine.hi.pengutronix.de ([2001:67c:670:100:3ad5:47ff:feaf:1a17] helo=lupine) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lHUJL-00017T-6G; Wed, 03 Mar 2021 17:25:19 +0100 Received: from pza by lupine with local (Exim 4.92) (envelope-from ) id 1lHUJK-0003MJ-Ef; Wed, 03 Mar 2021 17:25:18 +0100 Message-ID: Subject: Re: [PATCH v3 0/5] Reset driver for IMX8MQ VPU hardware block From: Philipp Zabel To: Benjamin Gaignard , robh+dt@kernel.org, shawnguo@kernel.org, s.hauer@pengutronix.de, festevam@gmail.com, ezequiel@collabora.com, mchehab@kernel.org, gregkh@linuxfoundation.org Cc: kernel@pengutronix.de, linux-imx@nxp.com, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org, devel@driverdev.osuosl.org, kernel@collabora.com Date: Wed, 03 Mar 2021 17:25:18 +0100 In-Reply-To: <2d55ad69-9b93-ab0e-04af-cd775cc9248b@collabora.com> References: <20210301151754.104749-1-benjamin.gaignard@collabora.com> <2d55ad69-9b93-ab0e-04af-cd775cc9248b@collabora.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT User-Agent: Evolution 3.30.5-1.1 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2001:67c:670:100:3ad5:47ff:feaf:1a17 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: devicetree@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Wed, 2021-03-03 at 16:20 +0100, Benjamin Gaignard wrote: > Le 03/03/2021 à 15:17, Philipp Zabel a écrit : > > Hi Benjamin, > > > > On Mon, 2021-03-01 at 16:17 +0100, Benjamin Gaignard wrote: > > > The two VPUs inside IMX8MQ share the same control block which can be see > > > as a reset hardware block. > > This isn't a reset controller though. The control block also contains > > clock gates of some sort and a filter register for the featureset fuses. > > Those shouldn't be manipulated via the reset API. > > They are all part of the control block and of the reset process for this > hardware that why I put them here. I guess it is border line :-) I'm pushing back to keep the reset control framework focused on controlling reset lines. Every side effect (such as the asymmetric clock ungating) in a random driver makes it harder to reason about behaviour at the API level, and to review patches for hardware I am not familiar with. > > > In order to be able to add the second VPU (for HECV decoding) it will be > > > more handy if the both VPU drivers instance don't have to share the > > > control block registers. This lead to implement it as an independ reset > > > driver and to change the VPU driver to use it. > > Why not switch to a syscon regmap for the control block? That should > > also allow to keep backwards compatibility with the old binding with > > minimal effort. > > I will give a try in this direction. Thank you. > > > Please note that this series break the compatibility between the DTB and > > > kernel. This break is limited to IMX8MQ SoC and is done when the driver > > > is still in staging directory. > > I know in this case we are pretty sure there are no users of this > > binding except for a staging driver, but it would still be nice to keep > > support for the deprecated binding, to avoid the requirement of updating > > kernel and DT in lock-step. > > If I want to use a syscon (or a reset) the driver must not ioremap the "ctrl" > registers. It means that "ctrl" has to be removed from the driver requested > reg-names (imx8mq_reg_names[]). Doing that break the kernel/DT compatibility. > Somehow syscon and "ctrl" are exclusive. The way the driver is set up currently, yes. You could add a bit of platform specific probe code, though, that would set up the regmap either by calling syscon_regmap_lookup_by_phandle(); for the new binding, or, if the phandle is not available, fall back to platform_get_resource_byname(..., "ctrl"); devm_ioremap_resource(); devm_regmap_init_mmio(); for the old binding. The actual codec .reset and variant .runtime_resume ops could be identical then. regards Philipp