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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 0A7E5C5B57D for ; Tue, 2 Jul 2019 08:14:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E054C205ED for ; Tue, 2 Jul 2019 08:14:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728500AbfGBIOE (ORCPT ); Tue, 2 Jul 2019 04:14:04 -0400 Received: from relay9-d.mail.gandi.net ([217.70.183.199]:58267 "EHLO relay9-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728121AbfGBIOC (ORCPT ); Tue, 2 Jul 2019 04:14:02 -0400 X-Originating-IP: 90.89.68.76 Received: from localhost (lfbn-1-10718-76.w90-89.abo.wanadoo.fr [90.89.68.76]) (Authenticated sender: maxime.ripard@bootlin.com) by relay9-d.mail.gandi.net (Postfix) with ESMTPSA id 29E16FF807; Tue, 2 Jul 2019 08:13:47 +0000 (UTC) Date: Tue, 2 Jul 2019 10:13:46 +0200 From: Maxime Ripard To: Andrzej Hajda Cc: Torsten Duwe , Harald Geyer , Vasily Khoruzhick , Chen-Yu Tsai , Rob Herring , Mark Rutland , Thierry Reding , David Airlie , Daniel Vetter , Laurent Pinchart , Icenowy Zheng , Sean Paul , Greg Kroah-Hartman , Thomas Gleixner , dri-devel , devicetree , arm-linux , linux-kernel Subject: Re: [PATCH v2 7/7] arm64: dts: allwinner: a64: enable ANX6345 bridge on Teres-I Message-ID: <20190702081346.4hlb53qcajhz4ckl@flea> References: <20190605120237.ekmytfxcwbjaqy3x@flea> <20190607062802.m5wslx3imiqooq5a@flea> <20190607094030.GA12373@lst.de> <66707fcc-b48e-02d3-5ed7-6b7e77d53266@samsung.com> <20190612152022.c3cfhp4cauhzhfyr@flea> <20190701095842.fvganvycce2cy7jn@flea> <64471471-5b4d-3c1f-a0e3-e02ee78ca23c@samsung.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ysvumhfqulaacx3l" Content-Disposition: inline In-Reply-To: <64471471-5b4d-3c1f-a0e3-e02ee78ca23c@samsung.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ysvumhfqulaacx3l Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Jul 01, 2019 at 02:27:51PM +0200, Andrzej Hajda wrote: > On 01.07.2019 11:58, Maxime Ripard wrote: > > On Fri, Jun 28, 2019 at 12:39:32PM +0200, Andrzej Hajda wrote: > >> On 12.06.2019 17:20, Maxime Ripard wrote: > >>>> I am not sure if I understand whole discussion here, but I also do not > >>>> understand whole edp-connector thing. > >>> The context is this one: > >>> https://patchwork.freedesktop.org/patch/257352/?series=51182&rev=1 > >>> https://patchwork.freedesktop.org/patch/283012/?series=56163&rev=1 > >>> https://patchwork.freedesktop.org/patch/286468/?series=56776&rev=2 > >>> > >>> TL;DR: This bridge is being used on ARM laptops that can come with > >>> different eDP panels. Some of these panels require a regulator to be > >>> enabled for the panel to work, and this is obviously something that > >>> should be in the DT. > >>> > >>> However, we can't really describe the panel itself, since the vendor > >>> uses several of them and just relies on the eDP bus to do its job at > >>> retrieving the EDIDs. A generic panel isn't really working either > >>> since that would mean having a generic behaviour for all the panels > >>> connected to that bus, which isn't there either. > >>> > >>> The connector allows to expose this nicely. > >> As VESA presentation says[1] eDP is based on DP but is much more > >> flexible, it is up to integrator (!!!) how the connection, power > >> up/down, initialization sequence should be performed. Trying to cover > >> every such case in edp-connector seems to me similar to panel-simple > >> attempt failure. Moreover there is no such thing as physical standard > >> eDP connector. Till now I though DT connector should describe physical > >> connector on the device, now I am lost, are there some DT bindings > >> guidelines about definition of a connector? > > This might be semantics but I guess we're in some kind of grey area? > > > > Like, for eDP, if it's soldered I guess we could say that there's no > > connector. But what happens if for some other board, that signal is > > routed through a ribbon? > > > > You could argue that there's no physical connector in both cases, or > > that there's one in both, or one for the ribbon and no connector for > > the one soldered in. > > This is not about ribbon vs soldering. It is about usage: this > connection is static across the whole life of the device (except > exceptional things: repair, non-standard usage, etc). It doesn't have to be. > And "the real connector" is (at least for me) something where > end-user can connect/disconnect different things: USB, HDMI, > ethernet, etc. And obviously to be functional it should be somehow > standardized. So even if there could be some grey area, I do not see > it here. Well, if there's a ribbon connector, then you have a physical connector, with the end user being able to connect / disconnect various displays. It might not be the case with actual products, but it's pretty common with SBCs to have that signal routed through a connector, and the user has several options to connect a display to it. The line really is blurred. > >> Maybe instead of edp-connector one would introduce integrator's specific > >> connector, for example with compatible "olimex,teres-edp-connector" > >> which should follow edp abstract connector rules? This will be at least > >> consistent with below presentation[1] - eDP requirements depends on > >> integrator. Then if olimex has standard way of dealing with panels > >> present in olimex/teres platforms the driver would then create > >> drm_panel/drm_connector/drm_bridge(?) according to these rules, I guess. > >> Anyway it still looks fishy for me :), maybe because I am not > >> familiarized with details of these platforms. > > > That makes sense yes > > And what if some panel can be used with this pseudo-connecter and in > some different hw directly? Code duplication? DT overlays? Overlays are a solution, but I would advocate to always have the connector. Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com --ysvumhfqulaacx3l Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRcEzekXsqa64kGDp7j7w1vZxhRxQUCXRsSOgAKCRDj7w1vZxhR xULUAPsGQYzNIZSTC25p24UViIRLulmthcOhzTK4JDdmTudgfAD+LA/mKeRDEVmr 5I2K+qvDzz8yXwdP9AtgR/XK8mhHSQ8= =dLkQ -----END PGP SIGNATURE----- --ysvumhfqulaacx3l--