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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 54B2CC433E6 for ; Wed, 17 Mar 2021 23:28:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 30FF064E98 for ; Wed, 17 Mar 2021 23:28:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229769AbhCQX1m (ORCPT ); Wed, 17 Mar 2021 19:27:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229829AbhCQX1k (ORCPT ); Wed, 17 Mar 2021 19:27:40 -0400 Received: from mail-pg1-x52d.google.com (mail-pg1-x52d.google.com [IPv6:2607:f8b0:4864:20::52d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 972F3C061760 for ; Wed, 17 Mar 2021 16:27:40 -0700 (PDT) Received: by mail-pg1-x52d.google.com with SMTP id o11so220066pgs.4 for ; Wed, 17 Mar 2021 16:27:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=ODgJlo11thr3abRRn5H88pJeZKbcK7WUWOM8GS7dn/E=; b=ka7O4tt5b/1Dj+gDV75rnKYCFDViijs6tPrSecl/kL4FE/l3HAn8wK2w7DCA/GvLMz vzLzimLuFdKdgF8qD04l6Hl6ELjSIJ2DmchyQZq+HAFFv7uXuz0J+WyWzxCsFodfyJMD JqVKZ2cm3qQs9iPt7qK9kDLHA527OLYf70mSw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=ODgJlo11thr3abRRn5H88pJeZKbcK7WUWOM8GS7dn/E=; b=mlE5+5NQXd0RrapgU+S8IZq9xw8dNR3+iQrF8C0eJJrqITA/b0EIVGarZhybqmwDEw sR7q12ofC7LjcdtLU2Eeb5Xca2C3kKc+8YDdOwD2QZRgnUao1ldVF6LaOD4acL68HxvU a2xXM6U0gWEydtDtAxnxMuK/wefWwcamJ1edV9YFuEpKKg/fxw3jsbiUbgCCi0MIY6Ln RfCK13TwRWmyyo4smooixxWfwxTzta23SxFz96ppeYg69/1Xg/axQI3t4IayOCyEvUPz vD5I4rZSbHXkvMxQdZrSgXFH/4U7cNLSfo7PjQDaxakp7yhx1EqtKUje9MriRY3crb8m E2IQ== X-Gm-Message-State: AOAM532qLe78FN/bkJ5ZP/+gtxTq4TwmkxGxeaHMAIJgqxOBUNR8GNd7 q1/XMocJG4uPyNdfjvE3pOQYwg== X-Google-Smtp-Source: ABdhPJzeS30ixDkVh9yP6I/NanMrQ/pjkgpILrw4pj9P0Ogh+/lOMqEh56QvyTw5PcFj2orL9mcEJA== X-Received: by 2002:aa7:8a58:0:b029:1fb:8ab:866e with SMTP id n24-20020aa78a580000b02901fb08ab866emr1339585pfa.0.1616023660024; Wed, 17 Mar 2021 16:27:40 -0700 (PDT) Received: from localhost ([2620:15c:202:1:3cf8:6a09:780b:f65d]) by smtp.gmail.com with UTF8SMTPSA id x186sm166239pfc.65.2021.03.17.16.27.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Mar 2021 16:27:39 -0700 (PDT) Date: Wed, 17 Mar 2021 16:27:37 -0700 From: Matthias Kaehlcke To: Douglas Anderson Cc: Bjorn Andersson , Rob Herring , Thierry Reding , Sam Ravnborg , robdclark@chromium.org, Daniel Vetter , dri-devel@lists.freedesktop.org, David Airlie , devicetree@vger.kernel.org, swboyd@chromium.org, linux-arm-msm@vger.kernel.org, Steev Klimaszewski , eballetbo@gmail.com, Andy Gross , Linus Walleij , drinkcat@chromium.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 1/3] dt-bindings: display: simple: Add the panel on sc7180-trogdor-pompom Message-ID: References: <20210316140707.RFC.1.I3a21995726282f1e9fcb70da5eb96f19ed96634f@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210316140707.RFC.1.I3a21995726282f1e9fcb70da5eb96f19ed96634f@changeid> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 16, 2021 at 02:08:19PM -0700, Douglas Anderson wrote: > The sc7180-trogdor-pompom board might be attached to any number of a > pile of eDP panels. At the moment I'm told that the list might include: > - KD KD116N21-30NV-A010 > - KD KD116N09-30NH-A016 > - Starry 2081116HHD028001-51D > - Sharp LQ116M1JW10 > > It should be noted that while the EDID programmed in the first 3 > panels indicates that they should run with exactly the same timing (to > keep things simple), the 4th panel not only needs different timing but > has a different resolution. > > As is true in general with eDP panels, we can figure out which panel > we have and all the info needed to drive its pixel clock by reading > the EDID. However, we can do this only after we've powered the panel > on. Powering on the panels requires following the timing diagram in > each panel's datasheet which specifies delays between certain > actions. This means that, while we can be quite dynamic about handling > things we can't just totally skip out on describing the panel like we > could do if it was connected to an external-facing DP port. > > While the different panels have slightly different delays, it's > possible to come up with a set of unified delays that will work on all > the panels. From reading the datasheets: > * KD KD116N21-30NV-A010 and KD KD116N09-30NH-A016 > - HPD absent delay: 200 ms > - Unprepare delay: 150 ms (datasheet is confusing, might be 500 ms) > * Starry 2081116HHD028001-51D > - HPD absent delay: 100 ms > - Enable delay: (link training done till enable BL): 200 ms > - Unprepare delay: 500 ms > * Sharp LQ116M1JW10 > - HPD absent delay: 200 ms > - Unprepare delay: 500 ms > - Prepare to enable delay (power on till backlight): 100 ms > > Unified: > - HPD absent delay: 200 ms > - Unprepare delay: 500 ms > - Enable delay: 200 ms > > NOTE: in theory the only thing that we _really_ need unity on is the > "HPD absent delay" since once the panel asserts HPD we can read the > EDID and could make per-panel decisions if we wanted. > > Let's create a definition of "a panel that can be attached to pompom" > as a panel that provides a valid EDID and can work with the standard > pompom power sequencing. If more panels are later attached to pompom > then it's fine as long as they work in a compatible way. > > One might ask why we can't just use a generic string here and provide > the timings directly in the device tree file. As I understand it, > trying to describe generic power sequencing in the device tree is > frowned upon and the one instance (SD/MMC) is regarded as a mistake > that shouldn't be repeated. Specifying a power sequence per board (or > per board class) feels like a reasonable compromise. We're not trying > to define fully generic power sequence bindings but we can also take > advantage of the semi-probable properties of the attached device. > > NOTE: I believe that past instances of supporting this type of thing > have used the "white lie" approach. One representative panel was > listed in the device tree. The power sequencings of this > representative panel were OK to use across all panels that might be > attached and other differences were handled by EDID. This patch > attempts to set a new precedent and avoid the need for the white lie. > > Signed-off-by: Douglas Anderson > --- Sounds reasonable to me if DT maintainers can live with this abstract hardware definition. It's clearer than the 'white lie' approach. It's then up to the vendor/manufacturer to ensure to only ship devices with panels that have compatible timings. > .../devicetree/bindings/display/panel/panel-simple.yaml | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml > index 62b0d54d87b7..9807dbc1cceb 100644 > --- a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml > +++ b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml > @@ -140,6 +140,10 @@ properties: > - giantplus,gpg48273qs5 > # GiantPlus GPM940B0 3.0" QVGA TFT LCD panel > - giantplus,gpm940b0 > + # A panel connected to a google,pompom board. Panel is guaranteed to > + # confirm to google,pompom-panel power sequencing requirements and then s/confirm/conform/ ? > + # the specific panel will be probed via EDID. > + - google,pompom-panel > # HannStar Display Corp. HSD070PWW1 7.0" WXGA TFT LCD panel > - hannstar,hsd070pww1 > # HannStar Display Corp. HSD100PXN1 10.1" XGA LVDS panel FWIW: Reviewed-by: Matthias Kaehlcke