From patchwork Thu Apr 23 16:25:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Doug Anderson X-Patchwork-Id: 11506029 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 C907513B2 for ; Thu, 23 Apr 2020 16:26:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B164F20781 for ; Thu, 23 Apr 2020 16:26:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="PZJbeCom" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729691AbgDWQ0T (ORCPT ); Thu, 23 Apr 2020 12:26:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1729685AbgDWQ0S (ORCPT ); Thu, 23 Apr 2020 12:26:18 -0400 Received: from mail-pj1-x1042.google.com (mail-pj1-x1042.google.com [IPv6:2607:f8b0:4864:20::1042]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AAD6FC09B043 for ; Thu, 23 Apr 2020 09:26:18 -0700 (PDT) Received: by mail-pj1-x1042.google.com with SMTP id a7so2721012pju.2 for ; Thu, 23 Apr 2020 09:26:18 -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=0pFOeS/sccEGP8eQs3DCcfXA0C9Qzm+B0/uziitxo7M=; b=PZJbeComGG7JDFOB1vq0Jdn+qnhdYrSl+H4jkTL11L9tYn72mUi7nGkoVSNEeSsD0g 027EsBScgUtwPBDQUwrSSERa/J98e9K2LZccHBgJsVTEnustjW2Ah+SmFQ0DuvzLwCdO f4jxVcisWbddJDGpXHycgtzYGooB/8jVRMDj4= 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=0pFOeS/sccEGP8eQs3DCcfXA0C9Qzm+B0/uziitxo7M=; b=OUt4C/VDsb77lXiAYUKUckxzvxaufgFezNl2R4IOwa83mRlhBBH+DBSPscMxo4yFvS Cyo/97YY6nW1407jocc0slvG1YcthdsDagZ+qoeF/80aBa7dedIRJKkCNDo7vDT4sr06 ix6Ly94X+LW9s00e7bt9dwETS1KeCECMeR6hZUop61iHdbtBzs+RO/Kl6egbpNvH0mUS J9fTZ3ky29NOndFus4L7383+Uz2BbWbnpmtVFF7Vi0dQpHYPPe8WmjZ0omlYHzN7Ko89 hC/YzkdFRoG/jtISjCAoGiMoHm9J68a6twlHHA+Q26JLod8xmGG4sCoQmjPkMKO5xyaX MaJg== X-Gm-Message-State: AGi0PuYKKRCXI3Sro0j7PJnWAqGqGZDDLZwX0q3KGwMtny4eJtj3yZJB jbvlp4QFdbxhieeHgQyPvl7R1A== X-Google-Smtp-Source: APiQypKCbPFY+Q4sglYBstzKdPED0nN/sooISbAltNPO+XiIHqjiLYy5Y1KMaCJ8PsAcOItdpeGcfg== X-Received: by 2002:a17:902:8eca:: with SMTP id x10mr4668468plo.60.1587659178165; Thu, 23 Apr 2020 09:26:18 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:202:1:24fa:e766:52c9:e3b2]) by smtp.gmail.com with ESMTPSA id d12sm2841927pfq.36.2020.04.23.09.26.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Apr 2020 09:26:17 -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: swboyd@chromium.org, devicetree@vger.kernel.org, linux-gpio@vger.kernel.org, jeffrey.l.hugo@gmail.com, dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, robdclark@chromium.org, jernej.skrabec@siol.net, jonas@kwiboo.se, bjorn.andersson@linaro.org, Douglas Anderson , linux-kernel@vger.kernel.org Subject: [PATCH v3 5/6] dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd Date: Thu, 23 Apr 2020 09:25:47 -0700 Message-Id: <20200423092431.v3.5.I72892d485088e57378a4748c86bc0f6c2494d807@changeid> X-Mailer: git-send-email 2.26.1.301.g55bc3eb7cb9-goog In-Reply-To: <20200423162548.129661-1-dianders@chromium.org> References: <20200423162548.129661-1-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 --- 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 | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml index 6d7d40ad45ac..5746416b0f73 100644 --- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml +++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml @@ -28,6 +28,10 @@ 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. + vccio-supply: description: A 1.8V supply that powers the digital IOs. @@ -207,6 +211,8 @@ examples: clocks = <&rpmhcc RPMH_LN_BB_CLK2>; clock-names = "refclk"; + no-hpd; + ports { #address-cells = <1>; #size-cells = <0>;