From patchwork Wed May 13 21:59:02 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Doug Anderson X-Patchwork-Id: 11547369 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 49A38139A for ; Wed, 13 May 2020 21:59:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 038C22078C for ; Wed, 13 May 2020 21:59:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="fe3R6CAU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729487AbgEMV71 (ORCPT ); Wed, 13 May 2020 17:59:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1730390AbgEMV7Z (ORCPT ); Wed, 13 May 2020 17:59:25 -0400 Received: from mail-pf1-x442.google.com (mail-pf1-x442.google.com [IPv6:2607:f8b0:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CDF4EC05BD0A for ; Wed, 13 May 2020 14:59:25 -0700 (PDT) Received: by mail-pf1-x442.google.com with SMTP id x2so338641pfx.7 for ; Wed, 13 May 2020 14:59:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=uWnq+06g1H9soD1qxhwQLI1N3tT7e79PiCY3gi5c9aM=; b=fe3R6CAU9akKfw4dtfUNsRdKf7Ag7zoIYxBqVogXiRrGwPU0QUp/9tNbaEemvZzD1L /T7Z5yqdRUT6l2ksQP+kuFuuu/B8IBMAdp9GYoKzOr+E1yoOhBqUT0eiCGWp5KMK0zvw Dc6KMgYU8E6iLb2l9O0cf5rGVtAkeLViaDji4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=uWnq+06g1H9soD1qxhwQLI1N3tT7e79PiCY3gi5c9aM=; b=SnoAUtzDE9Z/Pj/nWAhRR+Lp71a1b0U1fYn4/gQiPYe+TzaWR4pieD0hL8QZa686vv Xd2TIzCoFKSSgtjI2n04mFCDEwOFKQpkg0d5FWEfxrusdzWQ3op7ipS5V4dZVR9Czv0/ 5b7AqyuVvgnlEnFvBoRfe+vfIGx1+Hdjdu3V/SoYvTdyy+xA4xPIQ3R/eh9WiCx4tfLr PbUVyGBQ2h2Ai+XRDRskztOJiNnOfaY3QjrhvwL6fGMlhJBCAfdv7+ddiqPVSH5/lYUc CgopqWpClMw8pHM0bJZGpqvrKpFl4TUFn1CANc5xoDo3yEOPcXlCIKGjBmkb1CVZb/O+ b9xA== X-Gm-Message-State: AOAM532BItKrDNe0adV+N/gZ9RyXKkw0utEjZnxSSB5dkJK5QbxKWYR0 +elWzWON3QArLvCFc3uMSPzy8g== X-Google-Smtp-Source: ABdhPJzkZax8TyAVILaCvSJkjfp8FipP70nrl3ZYFbtA5yfhvakjUWoYp2finzJP9lX++dBHXGJ1rg== X-Received: by 2002:a62:1d48:: with SMTP id d69mr1299026pfd.102.1589407165323; Wed, 13 May 2020 14:59:25 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:202:1:24fa:e766:52c9:e3b2]) by smtp.gmail.com with ESMTPSA id k27sm547169pgb.30.2020.05.13.14.59.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 May 2020 14:59:24 -0700 (PDT) From: Douglas Anderson To: linus.walleij@linaro.org, bgolaszewski@baylibre.com, airlied@linux.ie, daniel@ffwll.ch, robh+dt@kernel.org, narmstrong@baylibre.com, a.hajda@samsung.com, Laurent.pinchart@ideasonboard.com, spanda@codeaurora.org Cc: 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, Douglas Anderson , Laurent Pinchart , linux-kernel@vger.kernel.org Subject: [PATCH v6 3/3] dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd Date: Wed, 13 May 2020 14:59:02 -0700 Message-Id: <20200513145807.v6.3.I72892d485088e57378a4748c86bc0f6c2494d807@changeid> X-Mailer: git-send-email 2.26.2.645.ge9eca65c58-goog In-Reply-To: <20200513215902.261547-1-dianders@chromium.org> References: <20200513215902.261547-1-dianders@chromium.org> MIME-Version: 1.0 Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org 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. [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 Reviewed-by: Rob Herring --- Changes in v6: None Changes in v5: None Changes in v4: - Tacked on "or is otherwise unusable." to description. Changes in v3: - useful implement => useful to implement Changes in v2: - ("dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd") new for v2. .../devicetree/bindings/display/bridge/ti,sn65dsi86.yaml | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml index 07d26121afca..be10e8cf31e1 100644 --- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml +++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml @@ -28,6 +28,12 @@ properties: maxItems: 1 description: GPIO specifier for GPIO1 pin on bridge (active low). + no-hpd: + type: boolean + description: + Set if the HPD line on the bridge isn't hooked up to anything or is + otherwise unusable. + vccio-supply: description: A 1.8V supply that powers the digital IOs. @@ -213,6 +219,8 @@ examples: clocks = <&rpmhcc RPMH_LN_BB_CLK2>; clock-names = "refclk"; + no-hpd; + ports { #address-cells = <1>; #size-cells = <0>;