From patchwork Tue Apr 21 05:06:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Doug Anderson X-Patchwork-Id: 11500459 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 6164414DD for ; Tue, 21 Apr 2020 05:07:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 469E0206D6 for ; Tue, 21 Apr 2020 05:07:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="nb65i71b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726733AbgDUFHK (ORCPT ); Tue, 21 Apr 2020 01:07:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46410 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726793AbgDUFG6 (ORCPT ); Tue, 21 Apr 2020 01:06:58 -0400 Received: from mail-pl1-x641.google.com (mail-pl1-x641.google.com [IPv6:2607:f8b0:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3EB3C03C1AE for ; Mon, 20 Apr 2020 22:06:56 -0700 (PDT) Received: by mail-pl1-x641.google.com with SMTP id g2so4833452plo.3 for ; Mon, 20 Apr 2020 22:06:56 -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=p9SfnrsRhMA/qPvuCsjST2mGoK17aHJlJJvkNnwd554=; b=nb65i71bMyNDvp+sdcmyJgCnTThio7pQpLfe/PPQVkHJ/cfg7Xh4a41TWSBJorv8ms V21yVwalCaHSaeWNNpHz0XKxo66L8p65pOWIn7p/PzepLjKs0URAh351pERxeBtIwcxH iK6pH884EqbLKw5aelWgQcFQPAyzp2BLlq/y4= 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=p9SfnrsRhMA/qPvuCsjST2mGoK17aHJlJJvkNnwd554=; b=RIHzkcaBcfCwZ9SA3StmREH4CNgez9D+kLKa+nrYiGoAYTGKGH9oQYnsVtL1c0ifGW 8M4kOW+YdqvZ4CJX7a1buPVp9JihILEUPKs5Mc6tMxVQKNG0MxxuAm8dm/lujdeCW7uo j1tA7zbOfaKJzEGTU/Gpa0YCkCKbSCHnAsoje0MwX6Ex38lbmZIyPYrpb38/ezRkP1QS m+KYKsBAhF0w8I69YRUUuQgyY17oscf4T2I4bXFPX7hqmZZH3Xi3z+QyNTM76AHGwzzh X5O7Nn+0fD85u6nJNzZHduL93apEX2kRGCrh4gFFTzcOrZANmZ6OvCYPA1BvAQoo9pad QLfw== X-Gm-Message-State: AGi0PubitPyayiaDByY1gqSnrmsLoNWIRMi0NbXdlgKNtEmTuHepoHuC DMFTXPw2mAn+0eJt9SA7nleWqw== X-Google-Smtp-Source: APiQypIcPc/1SW4//EIY6vMzbYE5uNKXPesknOT++/ig2GpFC2AsI7vNhOSyrjyGALx69V1hBVLx4Q== X-Received: by 2002:a17:90a:3a81:: with SMTP id b1mr3431181pjc.184.1587445616047; Mon, 20 Apr 2020 22:06:56 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:202:1:24fa:e766:52c9:e3b2]) by smtp.gmail.com with ESMTPSA id p68sm1184780pfb.89.2020.04.20.22.06.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Apr 2020 22:06:55 -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: jonas@kwiboo.se, jeffrey.l.hugo@gmail.com, linux-gpio@vger.kernel.org, linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, jernej.skrabec@siol.net, swboyd@chromium.org, bjorn.andersson@linaro.org, robdclark@chromium.org, Douglas Anderson , linux-kernel@vger.kernel.org Subject: [PATCH v2 5/6] dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd Date: Mon, 20 Apr 2020 22:06:21 -0700 Message-Id: <20200420220458.v2.5.I72892d485088e57378a4748c86bc0f6c2494d807@changeid> X-Mailer: git-send-email 2.26.1.301.g55bc3eb7cb9-goog In-Reply-To: <20200421050622.8113-1-dianders@chromium.org> References: <20200421050622.8113-1-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 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 --- 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>;