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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 B9D48C433E0 for ; Tue, 26 May 2020 22:22:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 927512088E for ; Tue, 26 May 2020 22:22:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590531746; bh=YbfyJJ+EFMCvOov6GqRANF8UzyOPGfMrh6ud3HC/OG8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=XzxmAU1SKpwKaP9ISnXBmN9S1QqodFfC3gIiICxuXJniyD8HYV3INu/c8M6TCr11/ +nlhU281EExs17Sg/aLyzhpPLHPYPemo/G9vQBdhClW2ueZcfWrX5j/A5zNPCfqmE6 7+NNnJFAqIOWgT89XZF0Kb0ZnAoSNnOv0zyd8C6o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389911AbgEZWW0 (ORCPT ); Tue, 26 May 2020 18:22:26 -0400 Received: from mail-il1-f193.google.com ([209.85.166.193]:44464 "EHLO mail-il1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389382AbgEZWWZ (ORCPT ); Tue, 26 May 2020 18:22:25 -0400 Received: by mail-il1-f193.google.com with SMTP id j3so22070110ilk.11; Tue, 26 May 2020 15:22:24 -0700 (PDT) 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=Ynq91C3bWjCUnWc0GV/GZg7ncDaeExN2lTxhHszV0qY=; b=YwusBZrMl4oejzhHGUEizHwgyFhuSMgKTXKMnBK4/kHx6uLOZiBBNP6Y6EtAHyuJJn +il9kMVjxm1/nBGzh+XqeyHwSyciJ7KPCOo5fNDUnBJra9g8tnNHU/UHlBz9bwZPU/rb R+TvRWxJmivgpaJfD6TXs67abV1uZTmfv6hQHxMq0feV/6DzaUHomxHxGr4yO6CMAivs XX74UUqQo5WxlNbzQ2/3NCaQEcMtdlSFcHrpU2SoGKWFUZOJFRIIueP4NaCT+H6ViLYO WSG9jjgFg87zX/XaP6b19neHGXh+V/5ZraUKjNMacoSHbDWg3wy3rkhVHgupcnwjcD80 H/OQ== X-Gm-Message-State: AOAM533u3K00Q1KwP7ZrhDhYAUf/W1rqQbCuWXrvEx42eN+Zw1k/OfVB 6rPmdT8Th/hxdUxipLkcXw== X-Google-Smtp-Source: ABdhPJz4zwTFycpM7xWxPlcIjR9So1dYYKyguqhio4ecnACld0RI8Pfko2UrIAIq7kJ0pfTEHAQqMw== X-Received: by 2002:a05:6e02:e46:: with SMTP id l6mr3316013ilk.1.1590531744025; Tue, 26 May 2020 15:22:24 -0700 (PDT) Received: from xps15 ([64.188.179.252]) by smtp.gmail.com with ESMTPSA id b18sm609005ilh.77.2020.05.26.15.22.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2020 15:22:23 -0700 (PDT) Received: (nullmailer pid 489202 invoked by uid 1000); Tue, 26 May 2020 22:22:22 -0000 Date: Tue, 26 May 2020 16:22:22 -0600 From: Rob Herring To: Douglas Anderson Cc: linus.walleij@linaro.org, bgolaszewski@baylibre.com, airlied@linux.ie, daniel@ffwll.ch, narmstrong@baylibre.com, a.hajda@samsung.com, Laurent.pinchart@ideasonboard.com, spanda@codeaurora.org, bjorn.andersson@linaro.org, dri-devel@lists.freedesktop.org, swboyd@chromium.org, devicetree@vger.kernel.org, jeffrey.l.hugo@gmail.com, jernej.skrabec@siol.net, linux-arm-msm@vger.kernel.org, robdclark@chromium.org, jonas@kwiboo.se, linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 3/3] dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd Message-ID: <20200526222222.GA467364@bogus> References: <20200513215902.261547-1-dianders@chromium.org> <20200513145807.v6.3.I72892d485088e57378a4748c86bc0f6c2494d807@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200513145807.v6.3.I72892d485088e57378a4748c86bc0f6c2494d807@changeid> Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Wed, May 13, 2020 at 02:59:02PM -0700, Douglas Anderson wrote: > The ti-sn65dsi86 MIPI DSI to eDP bridge chip has a dedicated hardware > HPD (Hot Plug Detect) pin on it, but it's mostly useless for eDP > because of excessive debouncing in hardware. Specifically there is no > way to disable the debouncing and for eDP debouncing hurts you because > HPD is just used for knowing when the panel is ready, not for > detecting physical plug events. > > Currently the driver in Linux just assumes that nobody has HPD hooked > up. It relies on folks setting the "no-hpd" property in the panel > node to specify that HPD isn't hooked up and then the panel driver > using this to add some worst case delays when turning on the panel. > > Apparently it's also useful to specify "no-hpd" in the bridge node so > that the bridge driver can make sure it's doing the right thing > without peeking into the panel [1]. This would be used if anyone ever > found it useful to implement support for the HW HPD pin on the bridge. > Let's add this property to the bindings. > > NOTES: > - This is somewhat of a backward-incompatible change. All current > known users of ti-sn65dsi86 didn't have "no-hpd" specified in the > bridge node yet none of them had HPD hooked up. This worked because > the current Linux driver just assumed that HPD was never hooked up. > We could make it less incompatible by saying that for this bridge > it's assumed HPD isn't hooked up _unless_ a property is defined, but > "no-hpd" is much more standard and it's unlikely to matter unless > someone quickly goes and implements HPD in the driver. > - It is sensible to specify "no-hpd" at the bridge chip level and > specify "hpd-gpios" at the panel level. That would mean HPD is > hooked up to some other GPIO in the system, just not the hardware > HPD pin on the bridge chip. I would say 'no-hpd' belongs wherever HPD is broken. So it may still make sense in the panel. (Otherwise, it needs to be removed from panel-common.yaml and some panel bindings, right?) > [1] https://lore.kernel.org/r/20200417180819.GE5861@pendragon.ideasonboard.com > > Signed-off-by: Douglas Anderson > Reviewed-by: Stephen Boyd > Reviewed-by: Linus Walleij > Reviewed-by: Laurent Pinchart > --- In any case, Reviewed-by: Rob Herring