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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 212C8C433FE for ; Sat, 23 Apr 2022 01:38:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231511AbiDWBlo (ORCPT ); Fri, 22 Apr 2022 21:41:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230240AbiDWBln (ORCPT ); Fri, 22 Apr 2022 21:41:43 -0400 Received: from mail-oa1-x33.google.com (mail-oa1-x33.google.com [IPv6:2001:4860:4864:20::33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B11F76213E for ; Fri, 22 Apr 2022 18:38:47 -0700 (PDT) Received: by mail-oa1-x33.google.com with SMTP id 586e51a60fabf-e67799d278so6604320fac.11 for ; Fri, 22 Apr 2022 18:38:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:in-reply-to:references:from:user-agent:date:message-id :subject:to:cc; bh=98Q4KjRvjXM0WQPHZUCc5YLZNElnBXI0Q4eC5MfmUig=; b=k9a6JGU17lPps5sbFfsmrztGSV/zL0+DC4LCy8hfnFFRNlK3hMnkZdQlhPTQtnmjRY 3wjBJTvJ5Vsx0dJpwdSNsAuJUz7h22PH0sQ+beTiWIJvsz+z/1ycgNfkuiMzJGyBtvbg cJVAUi1g0etBvKVT4kVNTt1YZMGIDFwFBrcyY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:in-reply-to:references:from :user-agent:date:message-id:subject:to:cc; bh=98Q4KjRvjXM0WQPHZUCc5YLZNElnBXI0Q4eC5MfmUig=; b=r4/TdH92Xxne0Iqyou/2P2//omY2YTGxWsydh6mT6TGaeYPOYH8cXux+x/eFqCJ/FH WSDnsvPz8PCsAPJzsVy5MSUsOuBukEI0YDDP8NSwI5tbN/X7wAXu7+7T5enXmJ/vZlbU sFBv4ifPUwzs+5IHki33VSY8qghMCanVxy728bOz8P1ZmL1DhVypGhbGqxG61OtvZAq4 a9a7yHxobES5hzFFu7lwNUcOnxzzhIzQy29orQ1IbKflPehb3i+Wfu3ZtFGsB96EJV9J jtf07c4xwwbZx6L8b3fHrmIG+/AeLdEord2pEyN8DSjJo24F2qyUuEn+skgF3ZggEUuQ GyEg== X-Gm-Message-State: AOAM531WCjHw1MLGsnr5Nz/36dBicwQFCyPeSk7pGHYxiJdik/KEAce4 NxZ/YeKKUSNlFpuQux6AL8n6W02q3wV/h6yBfgMfUQ== X-Google-Smtp-Source: ABdhPJwlNqj63PkZquQxnFkGieqNdLLQiY/83YWsqgq1LyL+nK1ybanQly0mL7jbdoUfgkPKLIFUeSjxb0+Oi7jnSBA= X-Received: by 2002:a05:6870:15ca:b0:e9:551:6d1c with SMTP id k10-20020a05687015ca00b000e905516d1cmr1868942oad.193.1650677927041; Fri, 22 Apr 2022 18:38:47 -0700 (PDT) Received: from 753933720722 named unknown by gmailapi.google.com with HTTPREST; Fri, 22 Apr 2022 18:38:46 -0700 MIME-Version: 1.0 In-Reply-To: <1650618666-15342-4-git-send-email-quic_sbillaka@quicinc.com> References: <1650618666-15342-1-git-send-email-quic_sbillaka@quicinc.com> <1650618666-15342-4-git-send-email-quic_sbillaka@quicinc.com> From: Stephen Boyd User-Agent: alot/0.10 Date: Fri, 22 Apr 2022 18:38:46 -0700 Message-ID: Subject: Re: [PATCH v9 3/4] drm/msm/dp: wait for hpd high before aux transaction To: Sankeerth Billakanti , devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: robdclark@gmail.com, seanpaul@chromium.org, quic_kalyant@quicinc.com, quic_abhinavk@quicinc.com, dianders@chromium.org, quic_khsieh@quicinc.com, bjorn.andersson@linaro.org, sean@poorly.run, airlied@linux.ie, daniel@ffwll.ch, dmitry.baryshkov@linaro.org, quic_vproddut@quicinc.com, quic_aravindh@quicinc.com, steev@kali.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Quoting Sankeerth Billakanti (2022-04-22 02:11:05) > The source device should ensure the sink is ready before proceeding to > read the sink capability or perform any aux transactions. The sink > will indicate its readiness by asserting the HPD line. The controller > driver needs to wait for the hpd line to be asserted by the sink before > it performs any aux transactions. > > The eDP sink is assumed to be always connected. It needs power from the > source and its HPD line will be asserted only after the panel is powered > on. The panel power will be enabled from the panel-edp driver and only > after that, the hpd line will be asserted. > > Whereas for DP, the sink can be hotplugged and unplugged anytime. The hpd > line gets asserted to indicate the sink is connected and ready. Hence > there is no need to wait for the hpd line to be asserted for a DP sink. > > Signed-off-by: Sankeerth Billakanti > Reviewed-by: Douglas Anderson > --- Reviewed-by: Stephen Boyd 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 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 14E47C433F5 for ; Sat, 23 Apr 2022 01:38:49 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 5AEA110E283; Sat, 23 Apr 2022 01:38:48 +0000 (UTC) Received: from mail-oa1-x35.google.com (mail-oa1-x35.google.com [IPv6:2001:4860:4864:20::35]) by gabe.freedesktop.org (Postfix) with ESMTPS id BA56C10E2D9 for ; Sat, 23 Apr 2022 01:38:47 +0000 (UTC) Received: by mail-oa1-x35.google.com with SMTP id 586e51a60fabf-e5e433d66dso10429519fac.5 for ; Fri, 22 Apr 2022 18:38:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:in-reply-to:references:from:user-agent:date:message-id :subject:to:cc; bh=98Q4KjRvjXM0WQPHZUCc5YLZNElnBXI0Q4eC5MfmUig=; b=k9a6JGU17lPps5sbFfsmrztGSV/zL0+DC4LCy8hfnFFRNlK3hMnkZdQlhPTQtnmjRY 3wjBJTvJ5Vsx0dJpwdSNsAuJUz7h22PH0sQ+beTiWIJvsz+z/1ycgNfkuiMzJGyBtvbg cJVAUi1g0etBvKVT4kVNTt1YZMGIDFwFBrcyY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:in-reply-to:references:from :user-agent:date:message-id:subject:to:cc; bh=98Q4KjRvjXM0WQPHZUCc5YLZNElnBXI0Q4eC5MfmUig=; b=bS3KPHhZGJW7d6NCOMvox95aufy/1PqGm8XqrBc5uaXw+qEuuf203HdzXFIESFGMHy Wh/4BK5P9hXlMnoosWTADEMIU7qlEQ774+LiBCFvDgcUdE1zgdNaMoPP/WNsTzrfoHz1 zy2yupzyfWO+Vh6an808/PCn3FEQX7cK4IyElzUJWBN5JMnfifEykbqQjlwvx6ra5CGl 8GPvT+alIN1foRiOsQW5erVyuQsSyyJO+kn++FZDzg8Y9ySsJkYVAL1kVrScvrztHSnx R5KJQxq5CGgC/Gl7L2zcVN+MvkF8QeP87XTZ9yb+RF6WH+nFNTiqBsU8Yv7+JEdKrgh4 s7Nw== X-Gm-Message-State: AOAM531nJJx7sWslmMVyU4lNIptDOL9vD5GH3h0FR9GjtQAXrcbgxXrP 6AUOkc6jMy/taoo3BC3cC9OSPPCdlQ8+czHV0LQ/Aw== X-Google-Smtp-Source: ABdhPJwlNqj63PkZquQxnFkGieqNdLLQiY/83YWsqgq1LyL+nK1ybanQly0mL7jbdoUfgkPKLIFUeSjxb0+Oi7jnSBA= X-Received: by 2002:a05:6870:15ca:b0:e9:551:6d1c with SMTP id k10-20020a05687015ca00b000e905516d1cmr1868942oad.193.1650677927041; Fri, 22 Apr 2022 18:38:47 -0700 (PDT) Received: from 753933720722 named unknown by gmailapi.google.com with HTTPREST; Fri, 22 Apr 2022 18:38:46 -0700 MIME-Version: 1.0 In-Reply-To: <1650618666-15342-4-git-send-email-quic_sbillaka@quicinc.com> References: <1650618666-15342-1-git-send-email-quic_sbillaka@quicinc.com> <1650618666-15342-4-git-send-email-quic_sbillaka@quicinc.com> From: Stephen Boyd User-Agent: alot/0.10 Date: Fri, 22 Apr 2022 18:38:46 -0700 Message-ID: Subject: Re: [PATCH v9 3/4] drm/msm/dp: wait for hpd high before aux transaction To: Sankeerth Billakanti , devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: quic_kalyant@quicinc.com, dianders@chromium.org, quic_vproddut@quicinc.com, airlied@linux.ie, quic_abhinavk@quicinc.com, steev@kali.org, quic_khsieh@quicinc.com, seanpaul@chromium.org, dmitry.baryshkov@linaro.org, quic_aravindh@quicinc.com, bjorn.andersson@linaro.org, sean@poorly.run Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Quoting Sankeerth Billakanti (2022-04-22 02:11:05) > The source device should ensure the sink is ready before proceeding to > read the sink capability or perform any aux transactions. The sink > will indicate its readiness by asserting the HPD line. The controller > driver needs to wait for the hpd line to be asserted by the sink before > it performs any aux transactions. > > The eDP sink is assumed to be always connected. It needs power from the > source and its HPD line will be asserted only after the panel is powered > on. The panel power will be enabled from the panel-edp driver and only > after that, the hpd line will be asserted. > > Whereas for DP, the sink can be hotplugged and unplugged anytime. The hpd > line gets asserted to indicate the sink is connected and ready. Hence > there is no need to wait for the hpd line to be asserted for a DP sink. > > Signed-off-by: Sankeerth Billakanti > Reviewed-by: Douglas Anderson > --- Reviewed-by: Stephen Boyd