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 E2A2DECAAD5 for ; Mon, 5 Sep 2022 19:27:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230321AbiIET1Z (ORCPT ); Mon, 5 Sep 2022 15:27:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232042AbiIET1I (ORCPT ); Mon, 5 Sep 2022 15:27:08 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0BF5A2A40A; Mon, 5 Sep 2022 12:26:32 -0700 (PDT) Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 75CB26BC; Mon, 5 Sep 2022 21:26:29 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1662405989; bh=izZvMBjhr/bvNoYQGDtF2V3g+eGXqt7u558BOi7zzh4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=o+X+vJW8hZaFFG6GuYfb8yA+ApbPr801obKPxgfofa5BhL0dumnOH/8rkgB+JFRdf a6RcVNtIShr2rQ9ifr+3TfCt0/OmkubtPNHf0OOshh950odmH/j0RY8m13X6Cb3MWl 4R7H4YRilHsKo+VuFBdldnshTX/Y7iB1TziRSBJ8= Date: Mon, 5 Sep 2022 22:26:14 +0300 From: Laurent Pinchart To: Francesco Dolcini Cc: Francesco Dolcini , Max Krummenacher , Max Krummenacher , Fabio Estevam , Krzysztof Kozlowski , Marcel Ziswiler , NXP Linux Team , Pengutronix Kernel Team , Philippe Schenker , Rob Herring , Sascha Hauer , Shawn Guo , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] arm64: dts: imx8mp-verdin: add dsi to hdmi functionality Message-ID: References: <20220901154051.1885509-1-max.oss.09@gmail.com> <20220902155720.GB5699@francesco-nb.int.toradex.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi Francesco, On Sat, Sep 03, 2022 at 02:47:43PM +0200, Francesco Dolcini wrote: > On Sat, Sep 03, 2022 at 03:24:51AM +0300, Laurent Pinchart wrote: > > On Fri, Sep 02, 2022 at 05:57:20PM +0200, Francesco Dolcini wrote: > > > Hello Laurent, > > > answering here for both patches (1/2 and 2/2). > > > > > > On Thu, Sep 01, 2022 at 09:07:49PM +0300, Laurent Pinchart wrote: > > > > On Thu, Sep 01, 2022 at 05:40:50PM +0200, Max Krummenacher wrote: > > > > > From: Max Krummenacher > > > > > > > > > > Add the hdmi connector present on the dsi to hdmi adapter now > > > > > required by the upstream lontium bridge driver. > > > > > The dsi to hdmi adapter is enabled in an device tree overlay. > > > > > > > > Shouldn't the connector also be in the overlay ? There's certainly no > > > > physical HDMI connector on the i.MX8MP Verdin SoM :-) > > > > > > Toradex DTS include and overlay files structure so far has been a little > > > bit different and not following the expectation you just stated here, > > > you can just check the current *toradex*dts* files and you'll see that there > > > is other stuff that is not strictly part of the module. > > > > > > Copying from a previous email thread on a very similar discussion [0] > > > some of the reasons: > > > > > > - The SoM dtsi representing not only the functionality implemented into > > > the SoM, but the whole connector pinout to the carrier makes very easy > > > to just include a different som.dtsi in the carrier board dts and just > > > switch SoM, for example from a colibri-imx6 to a colibri-imx7. > > > > That's fine, but I don't see how that's related to the issue at hand. > > The DSI to HDMI bridge wouldn't be present on either SoM, would it ? > > > > > - We avoid code duplication > > > > > > This is working for us pretty well so far and the majority of the users > > > of ours modules rely on this structure, we would prefer not to change that. > > > > It may work for your current use cases, but it doesn't make it right :-) > > Most of engineering is about compromise, being consistent with what we > did so far and the end-user experience need to be taken into account. Sure, and so do mainline requirements :-) > > Someone can integrate a Verdin SoM with a carrier board that has no DSI > > to HDMI (or LVDS) bridge, there should thus be no such device in the > > device tree. The SoM has DSI signals present on its connector, that's > > what the SoM .dtsi should expose. > > Just for the record Verdin i.MX8M Plus do have both HDMI and LVDS on the > connector (in addition to DSI) [1], of course we do have also the option to > have LVDS or HDMI using an external add-on DSI bridge as this patches are > about. > > Said that it's true that sometime we describe peripherals that are part of the > SOM family into the SOM dtsi, this avoid quite a lot of duplications given the > amount of carrier board that are available on the market that use just the same > building blocks (and this was one of the 2 points I mentioned as a reasoning > for our current DTS files structure). If those "SoM family" peripherals are on the carrier board, what's the issue with describing them in the carrier board .dtsi ? And if they're on an add-on board (such as, if I understand correctly, the DSI to HDMI encoder for the Dahlia carrier board), what's the issue with describing them in an overlay ? > Of course, we keep these stuff disabled by default, so apart for some small size > increase I do not see a real issue. It's the same issue as adding any DT node for peripherals that do not exist, I fail to see a compelling reason to do so here, given that this seems to be easy to handle in the carrier board .dtsi or in overlays. Maybe I'm missing something ? > [1] https://docs.toradex.com/110977-verdin_imx8m_plus_v1.1_datasheet.pdf -- Regards, Laurent Pinchart