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[209.85.221.53]) by smtp.gmail.com with ESMTPSA id u6-20020a170906124600b006e843964f9asm540774eja.55.2022.04.07.17.20.47 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Apr 2022 17:20:48 -0700 (PDT) Received: by mail-wr1-f53.google.com with SMTP id u3so10552034wrg.3 for ; Thu, 07 Apr 2022 17:20:47 -0700 (PDT) X-Received: by 2002:a5d:674d:0:b0:206:163c:f70c with SMTP id l13-20020a5d674d000000b00206163cf70cmr12433627wrw.679.1649377247367; Thu, 07 Apr 2022 17:20:47 -0700 (PDT) MIME-Version: 1.0 References: <1648656179-10347-1-git-send-email-quic_sbillaka@quicinc.com> <1648656179-10347-2-git-send-email-quic_sbillaka@quicinc.com> <392b933f-760c-3c81-1040-c514045df3da@linaro.org> <3e5fa57f-d636-879a-b98f-77323d07c156@linaro.org> In-Reply-To: From: Doug Anderson Date: Thu, 7 Apr 2022 17:20:34 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v6 1/8] drm/msm/dp: Add eDP support via aux_bus To: Dmitry Baryshkov Cc: Abhinav Kumar , "Sankeerth Billakanti (QUIC)" , quic_kalyant , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , quic_vproddut , David Airlie , linux-arm-msm , "Kuogee Hsieh (QUIC)" , freedreno , dri-devel , "bjorn.andersson@linaro.org" , Sean Paul , "Aravind Venkateswaran (QUIC)" , Stephen Boyd , Sean Paul , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hi, On Thu, Apr 7, 2022 at 4:36 PM Dmitry Baryshkov wrote: > > The ps8640 driver looks 'working by coincidence'. It calls > dp_aux_populate, then immediately after the function returns it checks > for the panel. If panel-edp is built as a module, the probe might fail > easily. > The anx7625 driver has the same kind of issue. The DP AUX bus is > populated from the probe() and after some additional work the panel is > being checked. > This design is fragile and from my quick glance it can break (or be > broken) too easy. It reminds me of our drm msm 'probe' loops > preventing the device to boot completely if the dsi bridge/panel could > not be probed in time. I did spend some time thinking about this, at least for ps8640. I believe that as long as the panel's probe isn't asynchronous. Basically if the panel isn't ready then ps8640 should return and we'll retry later. I do remember the probe loops that we used to have with msm and I don't _think_ this would trigger it. That being said, if we need to separate out the AUX bus into a sub-device like we did in sn65dsi86 we certainly could. -Doug 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 0DB07C433F5 for ; Fri, 8 Apr 2022 00:20:53 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 6306A10EE6D; Fri, 8 Apr 2022 00:20:52 +0000 (UTC) Received: from mail-ej1-x641.google.com (mail-ej1-x641.google.com [IPv6:2a00:1450:4864:20::641]) by gabe.freedesktop.org (Postfix) with ESMTPS id 64E5610EE6D for ; Fri, 8 Apr 2022 00:20:50 +0000 (UTC) Received: by mail-ej1-x641.google.com with SMTP id bh17so14093658ejb.8 for ; Thu, 07 Apr 2022 17:20:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=EUO4ZkagqI35g4dyGZeSriotv9HvxG7vujGEgbCcZkU=; b=TEef53cSAydlsremUikPhSFLztWvs7WNKJRSiFhTfUee8wYEynR3p69EEhAbLFPoHE b29Gzz98Zuy76c+968HMXG1B9jQMg4QDHrYN4LM3amlXHkzn5hT+Pf77Sa8oH5mwkTxV oBPd9oZf+Ph6Z2N5mV3Z4xjh9ozw8I7/7moPc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=EUO4ZkagqI35g4dyGZeSriotv9HvxG7vujGEgbCcZkU=; b=UkADjp5ovXpg8ujCTc85ldHSGuujt0DdOUL3E1omJ/+qlmKFLuGgYkZUDZsUwjXDby ZQFsu9sXvnIF2EJ6R7ovD+1tZzbd3n8e1t9VlhefWz7Ez/mIcm6v23LzOL8SDJvAElMm rz8hEX9WCTvLCHiuhWxp1RQKF3tlma1qxFRWtkJHUsz5WQw2QPIMwILE3TdHndM8Vgxz RSxC2OCKmT210lx7YbhDkiRFeVhhrqUYD1qQxOyrSxgq+3SZhOgqILYwnMH6P3Y/bIgR gVcHSYqxen2weD7BfPxdGGhJkvIN7cS9LX8PlyhqDHh+kIDcK/WSZZ8NvlQickfRva52 hfag== X-Gm-Message-State: AOAM533s3e/njhvbOGx9qxTeveauA2dyBmcRpNDl9H9qasJMcoP56foc wdt5CAKKUXAzmby4xCY8aYcntpOaKvUVkEelH8s= X-Google-Smtp-Source: ABdhPJyDrBpS4/6aK0y0G4ms6n6yJevV8d6rQP12zyLncH+kZ2grGTqd3pQrzAmnvaVi/AWbpkzr5Q== X-Received: by 2002:a17:907:6093:b0:6e0:dabf:1a9f with SMTP id ht19-20020a170907609300b006e0dabf1a9fmr15953378ejc.424.1649377249010; Thu, 07 Apr 2022 17:20:49 -0700 (PDT) Received: from mail-wr1-f50.google.com (mail-wr1-f50.google.com. [209.85.221.50]) by smtp.gmail.com with ESMTPSA id j8-20020aa7c0c8000000b0041934547989sm9916062edp.55.2022.04.07.17.20.48 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Apr 2022 17:20:48 -0700 (PDT) Received: by mail-wr1-f50.google.com with SMTP id z1so10537200wrg.4 for ; Thu, 07 Apr 2022 17:20:48 -0700 (PDT) X-Received: by 2002:a5d:674d:0:b0:206:163c:f70c with SMTP id l13-20020a5d674d000000b00206163cf70cmr12433627wrw.679.1649377247367; Thu, 07 Apr 2022 17:20:47 -0700 (PDT) MIME-Version: 1.0 References: <1648656179-10347-1-git-send-email-quic_sbillaka@quicinc.com> <1648656179-10347-2-git-send-email-quic_sbillaka@quicinc.com> <392b933f-760c-3c81-1040-c514045df3da@linaro.org> <3e5fa57f-d636-879a-b98f-77323d07c156@linaro.org> In-Reply-To: From: Doug Anderson Date: Thu, 7 Apr 2022 17:20:34 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v6 1/8] drm/msm/dp: Add eDP support via aux_bus To: Dmitry Baryshkov 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 , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , "Sankeerth Billakanti \(QUIC\)" , quic_vproddut , David Airlie , linux-arm-msm , Stephen Boyd , Abhinav Kumar , dri-devel , "Kuogee Hsieh \(QUIC\)" , Sean Paul , Sean Paul , "Aravind Venkateswaran \(QUIC\)" , "bjorn.andersson@linaro.org" , freedreno , LKML Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi, On Thu, Apr 7, 2022 at 4:36 PM Dmitry Baryshkov wrote: > > The ps8640 driver looks 'working by coincidence'. It calls > dp_aux_populate, then immediately after the function returns it checks > for the panel. If panel-edp is built as a module, the probe might fail > easily. > The anx7625 driver has the same kind of issue. The DP AUX bus is > populated from the probe() and after some additional work the panel is > being checked. > This design is fragile and from my quick glance it can break (or be > broken) too easy. It reminds me of our drm msm 'probe' loops > preventing the device to boot completely if the dsi bridge/panel could > not be probed in time. I did spend some time thinking about this, at least for ps8640. I believe that as long as the panel's probe isn't asynchronous. Basically if the panel isn't ready then ps8640 should return and we'll retry later. I do remember the probe loops that we used to have with msm and I don't _think_ this would trigger it. That being said, if we need to separate out the AUX bus into a sub-device like we did in sn65dsi86 we certainly could. -Doug