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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A11B8C433EF for ; Tue, 28 Sep 2021 01:13:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B053611EF for ; Tue, 28 Sep 2021 01:13:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238408AbhI1BP3 (ORCPT ); Mon, 27 Sep 2021 21:15:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37976 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238399AbhI1BP2 (ORCPT ); Mon, 27 Sep 2021 21:15:28 -0400 Received: from mail-yb1-xb33.google.com (mail-yb1-xb33.google.com [IPv6:2607:f8b0:4864:20::b33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 13A24C061604 for ; Mon, 27 Sep 2021 18:13:50 -0700 (PDT) Received: by mail-yb1-xb33.google.com with SMTP id s18so13628570ybc.0 for ; Mon, 27 Sep 2021 18:13:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=JMP8/jcNVbgUKp5ottGBOH6ROq2ghuCbHnEvvMx2DcE=; b=GwJcgXgoUY0n5wyCG5U8GbrVKU+7VWBwoyP15sMmcEbMbp0JcnjSgLEczWWRNymt10 SCh2KPZZLYsunY7qXfpBfXF+wqo4OUZiXOX69sybpkKaSM7wrAvzaomsbyscKupxk4Cg fRmhUT9loHlpcGMu7ctf4ldYIrdsOo7ZPPZW9Jpv8HK1N4VyyWpHrL+tQAYqyCYOll+E csJPTTOdsyf0OsU6PKNzcjnblpOko5ZITq0OopHqRSmA/2P/PmHyN4qOhilwVGJZCj37 QIpnCSiJqznGsp1IEqZrOU1bm+lkz3Qn3fbzPC8aibxvftmJdujj8saXdCLCkqiFZz2m lvBQ== 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=JMP8/jcNVbgUKp5ottGBOH6ROq2ghuCbHnEvvMx2DcE=; b=ccNNjQqYIWIpt72IftUbvapaYKO/QVApBMqxx2xZBZrkY/O64NjzcTQywkL9nvCKR1 evINzzG4UC7eRZ9qNG8bWsazOeADfFc1Vkkslx65Opwhu3Zp7HwQMhVEo74dAkDUXfp0 KehCevAIlZ5LWnhz6kXrKaqaP+ndkj8dbGtCLmQj9VlZ4nobzkxEktBpE2w/uenDf4xk czsr9jo9UsJqNFLimt1Afr4RIgJ+l8uLMkf6ibEAhrl1aDyAG5n4TBUpzJuYz1O07ojB FV2vuQSyDWPOjQPf8DFmS/vva6V/nf5uogC6cSIkKHAYLJ+4g4FLxiywd6fYBIaRZMWN +9UQ== X-Gm-Message-State: AOAM533O94qXTLoDaogsDnHI27TAtY/uVCSSISmBCQ5x0c71HOZPsyCh 0Bzc+PK0iu+SIwOGp9D1EYrzlc4Gm3pLn6ByBehItw== X-Google-Smtp-Source: ABdhPJzQyGJm63+JJmaD2mRWs8l8vLrMn7uFvwpsLjqTUQacoMAgwEMboOVHnWxhEuzNXVZ/xtfUlSk7OGm+aLqK4WQ= X-Received: by 2002:a25:2b07:: with SMTP id r7mr3032498ybr.296.1632791628908; Mon, 27 Sep 2021 18:13:48 -0700 (PDT) MIME-Version: 1.0 References: <20210927204830.4018624-1-dmitry.baryshkov@linaro.org> <11fe1793-1455-ae44-b213-9afe47dfa370@linaro.org> In-Reply-To: <11fe1793-1455-ae44-b213-9afe47dfa370@linaro.org> From: Saravana Kannan Date: Mon, 27 Sep 2021 18:13:12 -0700 Message-ID: Subject: Re: [PATCH] Revert "of: property: fw_devlink: Add support for remote-endpoint" To: Dmitry Baryshkov Cc: Rob Herring , Frank Rowand , Greg Kroah-Hartman , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Stephen Boyd , linux-arm-msm Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Mon, Sep 27, 2021 at 5:56 PM Dmitry Baryshkov wrote: > > [Adding Stephen and linux-arm-msm to the CC list, missed on the patch Cc > list] > > On 28/09/2021 00:58, Saravana Kannan wrote: > > On Mon, Sep 27, 2021 at 1:48 PM Dmitry Baryshkov > > wrote: > >> > >> Since the commit f7514a663016 ("of: property: fw_devlink: Add support > >> for remote-endpoint") Linux kernel started parsing and adding devlinks > >> for the remote-endpoint properties. However this brings more harm than > >> good. > >> > >> For all the remote-endpoints in the graph two links are created. Thus > >> each and every remote-endpoint ends up in the cyclic graph (instead of > >> the original intent of catching a cycle of graph + non-graph link): > > > > Yes, I'm well aware of this. I even called this out in the commit > > text. This creating of cycles and then catching and relaxing it is > > intentional. > > https://lore.kernel.org/all/20210330185056.1022008-1-saravanak@google.com/ > > What would be the reason two always create a cycle which gives no > additional information? Maybe I'm just misunderstanding this piece of code. It's basically a tiny bit of busy work. Ulf and I planned to fix it and we know how to. Just haven't gotten around to it since it doesn't really break anything. > Regarding your commit message. Even if there is a non-remote-endpoint > dependency, it will be hidden by the remote-endpoint cycle. That's the point. Because there's no way to tell without the driver involvement, we basically need to ignore all dependencies between those two devices pointing at each other. > > And another consequence of remote-endpoint loops. > > Consider this part part of dmesg. One warning is correct (real cyclic > dependency). Others are remote-endpoint spam. Can you spot, which ones? > > [ 7.032225] platform 1d87000.phy: Fixing up cyclic dependency with > 1d84000.ufshc > [ 21.760326] platform c440000.spmi:pmic@2:typec@1500: Fixing up cyclic > dependency with c440000.spmi:pmic@2:pmic-tcpm > [ 21.944849] platform c440000.spmi:pmic@2:pdphy@1700: Fixing up cyclic > dependency with c440000.spmi:pmic@2:pmic-tcpm > [ 23.541968] platform a600000.usb: Fixing up cyclic dependency with > c440000.spmi:pmic@2:pmic-tcpm > [ 30.354170] i2c 5-002b: Fixing up cyclic dependency with hdmi-out It's info, not warning if I'm not mistaken. If that's really a problem we can make it a debug log. Not the end of the world. > > > >> > >> [ 0.381057] OF: remote-endpoint linking /soc@0/geniqup@9c0000/i2c@994000/hdmi-bridge@2b to /soc@0/mdss@ae00000/dsi@ae94000/ports/port@1/endpoint > >> [ 0.394421] OF: remote-endpoint linking /soc@0/geniqup@9c0000/i2c@994000/hdmi-bridge@2b to /hdmi-out/port/endpoint > >> [ 0.407007] OF: remote-endpoint linking /soc@0/phy@88e9000 to /soc@0/spmi@c440000/pmic@2/pmic-tcpm/connector/ports/port@0/endpoint@0 > >> [ 0.419648] OF: remote-endpoint linking /soc@0/usb@a6f8800/usb@a600000 to /soc@0/spmi@c440000/pmic@2/pmic-tcpm/ports/port@2/endpoint@0 > >> [ 0.432578] OF: remote-endpoint linking /soc@0/cci@ac4f000/i2c-bus@1/cam1@c0 to /soc@0/camss@ac6a000/ports/port@1/endpoint > >> [ 0.444450] OF: remote-endpoint linking /soc@0/camss@ac6a000 to /soc@0/cci@ac4f000/i2c-bus@1/cam1@c0/port/endpoint > >> [ 0.455292] OF: remote-endpoint linking /soc@0/mdss@ae00000/mdp@ae01000 to /soc@0/mdss@ae00000/dsi@ae94000/ports/port@0/endpoint > >> [ 0.467210] OF: remote-endpoint linking /soc@0/mdss@ae00000/mdp@ae01000 to /soc@0/mdss@ae00000/dsi@ae96000/ports/port@0/endpoint > >> [ 0.479239] OF: remote-endpoint linking /soc@0/mdss@ae00000/dsi@ae94000 to /soc@0/mdss@ae00000/mdp@ae01000/ports/port@0/endpoint > >> [ 0.491147] OF: remote-endpoint linking /soc@0/mdss@ae00000/dsi@ae94000 to /soc@0/geniqup@9c0000/i2c@994000/hdmi-bridge@2b/ports/port@0/endpoint > >> [ 0.504979] OF: remote-endpoint linking /soc@0/spmi@c440000/pmic@2/typec@1500 to /soc@0/spmi@c440000/pmic@2/pmic-tcpm/ports/port@0/endpoint > >> [ 0.517958] OF: remote-endpoint linking /soc@0/spmi@c440000/pmic@2/pdphy@1700 to /soc@0/spmi@c440000/pmic@2/pmic-tcpm/ports/port@1/endpoint > >> [ 0.565326] OF: remote-endpoint linking /hdmi-out to /soc@0/geniqup@9c0000/i2c@994000/hdmi-bridge@2b/ports/port@2/endpoint > >> > >> Under some conditions the device can become it's own supplier, > >> preventing this device to be probed at all: > > > > I'm not sure this analysis is correct -- this shouldn't be happening. > > If you go to the device link folder and cat "sync_state_only", I > > expect it to be "1" in this case. Can you confirm that? > > It is "1". Thanks for confirming. > > > Which means it won't block probing. Yes, the link itself is useless > > and it'll get auto deleted once mdss probes and it's easy to not > > create it in the first place. But this is definitely not your issue. > > > >> $ ls -l /sys/bus/platform/devices/ae00000.mdss/ > >> lrwxrwxrwx 1 root root 0 Aug 4 15:13 consumer:platform:ae00000.mdss -> ../../../virtual/devlink/platform:ae00000.mdss--platform:ae00000.mdss > >> > >> I think that until of_link can be tought to handle bi-directional links > >> on its own, we should not parse remote-endpoint properties. Thus the > >> aforementioned commit should be reverted. > > > > Nak. remote-endpoint parsing is working as intended. I don't think the > > analysis is correct. > > > > Can you please enable the logs in all these functions and attach the > > log so we can see why it's not probing mdss? > > device_link_add > > device_links_check_suppliers > > func fw_devlink_relax_link > > fw_devlink_create_devlink > > After doing the analysis, I can confirm that I was too quick regarding > the mdss links preventing it from being probed. Sorry about that. > > It all went up to the DP phy having a link with usb-c-connector. I was > running the kernel 5.15-rc1, so your tcpm fix is already present. > However my colleague has disabled the tcpm device (which I did not > notice). So the driver did not call fw_devlink_purge_absent_suppliers(). > The devlink still exists: Let me take a closer look at this before the end of this week. Can you point me to the exact DT changes that were made that's causing this issue? It should help me debug the issue. I have a guess on what the issue might be. > > [ 53.426446] platform 88e9000.phy: probe deferral - wait for supplier > connector > > However it is not present in the sysfs: Right, because it's not a device link yet. It's waiting for the device to show up to create the device link (it has to for the grand scheme of things to work correctly). > > root@qcom-armv8a:~# ls -l /sys/bus/platform/devices/88e9000.phy/ > lrwxrwxrwx 1 root root 0 Aug 4 15:13 > consumer:platform:a600000.usb -> > ../../../virtual/devlink/platform:88e9000.phy--platform:a600000.usb > lrwxrwxrwx 1 root root 0 Aug 4 15:13 > consumer:platform:af00000.clock-controller -> > ../../../virtual/devlink/platform:88e9000.phy--platform:af00000.clock-controller > -rw-r--r-- 1 root root 4096 Aug 4 15:13 driver_override > -r--r--r-- 1 root root 4096 Aug 4 15:13 modalias > lrwxrwxrwx 1 root root 0 Aug 4 15:13 of_node -> > ../../../../firmware/devicetree/base/soc@0/phy@88e9000 > drwxr-xr-x 2 root root 0 Aug 4 15:13 power > lrwxrwxrwx 1 root root 0 Aug 4 15:10 subsystem -> > ../../../../bus/platform > lrwxrwxrwx 1 root root 0 Aug 4 15:13 > supplier:platform:100000.clock-controller -> > ../../../virtual/devlink/platform:100000.clock-controller--platform:88e9000.phy > lrwxrwxrwx 1 root root 0 Aug 4 15:13 > supplier:platform:18200000.rsc:clock-controller -> > ../../../virtual/devlink/platform:18200000.rsc:clock-controller--platform:88e9000.phy > lrwxrwxrwx 1 root root 0 Aug 4 15:13 > supplier:platform:18200000.rsc:pm8150-rpmh-regulators -> > ../../../virtual/devlink/platform:18200000.rsc:pm8150-rpmh-regulators--platform:88e9000.phy > -rw-r--r-- 1 root root 4096 Aug 4 15:10 uevent > -r--r--r-- 1 root root 4096 Aug 4 15:13 > waiting_for_supplier > > Thus it is not possible to spot this device link without > CONFIG_DEBUG_DRIVER=y (or any similar debugging technique). I sent out some patches to make this easier. But doesn't look like it'll land in 5.15. https://lore.kernel.org/lkml/20210915172808.620546-1-saravanak@google.com/ > If I re-enabled tcpm device or if I reverted remote-endpoint parsing, DP > PHY probing would go fine. The DP PHY does not really depend on the > connector (or TCPM) being present in the system. The driver will > continue working w/o it. However it does not have a change to declare that. > > Furthermore I went back to the original case that caused you to add > remote-endpoint support. The DSI-eDP bridge and eDP panel using the GPIO > provided by that bridge. I think the proper fix for the original problem > was implemented by the commit bf73537f411b ("drm/bridge: ti-sn65dsi86: > Break GPIO and MIPI-to-eDP bridge into sub-drivers"). It split the > DSI-eDP bridge driver into functional parts (devices), so that GPIO part > and eDP parts are independent, thus breaking this cyclic dependency in a > functional way. The remote-endpoint parsing is no longer necessary in > this case (Stephen, please correct me if I'm wrong). Even if the original case doesn't need remote-endpoint to work correctly and the cycle has been broken, that doesn't remove the need for parsing remote-endpoint. There could be other cases like the original case. > I still think that remote endpoint parsing does more harm and noise than > good and thus should be reverted. I'll agree to disagree. I'm sure your issue can be fixed without removing support for remote-endpoint parsing -- let's work on that (I've asked for more details above). -Saravana