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 X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EFF3FC433ED for ; Thu, 20 May 2021 20:23:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C6889613AA for ; Thu, 20 May 2021 20:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236414AbhETUYu (ORCPT ); Thu, 20 May 2021 16:24:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236245AbhETUYu (ORCPT ); Thu, 20 May 2021 16:24:50 -0400 Received: from mail-yb1-xb2d.google.com (mail-yb1-xb2d.google.com [IPv6:2607:f8b0:4864:20::b2d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3990AC061574 for ; Thu, 20 May 2021 13:23:28 -0700 (PDT) Received: by mail-yb1-xb2d.google.com with SMTP id r8so24502853ybb.9 for ; Thu, 20 May 2021 13:23:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=MVYvG69dM0fC6VHqsM41A8Q/ztvt7bvyrWxB/84zXpw=; b=A6H7F4mJDsj+qJsCnEUjuVaB8RyyVctXtD8OEjFgx4Caknyq5y4GXQWtPArqrNBZvx 00x7IwQs2lF+CLqDcks5Ukf76T0DSEHGHC2q1XlqJnc/pN0wKDkzbITh6OwuOOcJRXK6 NI5vll/QrZvokRHTdDIdw0XaPF3coyQxTbSmapQg93cX9LqkJg9pKOemiXcFJRFDzYqf GP5E/yBsjPVM+9mUFZl9dHRxuu1NYCvCDr7rh/6mm9ybi4b8npSsKgzYSHrbGZYnxlra U/VM2IWY0rdUEvICRxR6xZUp/KxfSfq+k7Vg65Dy1XSeegBUKtJ/J3FWEVIYxah+3CYY L5Zw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=MVYvG69dM0fC6VHqsM41A8Q/ztvt7bvyrWxB/84zXpw=; b=izfhU5rqGPP5vyQhlQFMSbTHSWEzup/xdX5wghE4f9Qcn00vb9MVlPxbfusrM4ywzK q53JywRUXdIDJXNn8ydOs1P4J089yMQ3G31i6n70GhA2uNKfOyVYQX9ZV0WtfzeCuQp4 KDIliB+y1ZN8kzAJu9erZtITtOq+nJ23z2AxDlEs0De/j3DvoyQiGy6gJetFse3yCoBt vvqY+6K3yr9x2SjReiqV7E8DLL1E80YwES8RQ1ydz/2GpcCLR8jhuaM42P5xox/N/vIr xz5vZhtc/aRyYG72D18uItW29FAowhQA2arSvAyD/NH//O2q/J9KG+s50U5C4IstRU0Q Wrnw== X-Gm-Message-State: AOAM530WF+LmxefNZBhH/V5qAfxQBiCUiyxFXB1N9bxpTTM6xC+Go1sD AXVVlOZSzMHU/VlWVQ96C59M13bbEBh6KfpU7GJDjQ== X-Google-Smtp-Source: ABdhPJwqDvRHLda2COB+ayK+YS4pv2lYnwtWyCrePqkFPUARyDA8/lJFmO/4FGC9m8jWuLHZjcHB5N4s1GVhyCasHhQ= X-Received: by 2002:a25:3f47:: with SMTP id m68mr9474846yba.228.1621542207016; Thu, 20 May 2021 13:23:27 -0700 (PDT) MIME-Version: 1.0 References: <20210520002519.3538432-1-swboyd@chromium.org> <20210520002519.3538432-8-swboyd@chromium.org> In-Reply-To: From: Saravana Kannan Date: Thu, 20 May 2021 13:22:51 -0700 Message-ID: Subject: Re: [PATCH 7/7] drm/msm: Migrate to aggregate driver To: Stephen Boyd , Greg Kroah-Hartman , LKML , linux-arm-msm , dri-devel , freedreno , "Rafael J. Wysocki" , Rob Clark , Russell King , Saravana Kannan Cc: Daniel Vetter Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Thu, May 20, 2021 at 12:58 PM Daniel Vetter wrote: > > On Wed, May 19, 2021 at 05:25:19PM -0700, Stephen Boyd wrote: > > The device lists are poorly ordered when the component device code is > > used. This is because component_master_add_with_match() returns 0 > > regardless of component devices calling component_add() first. It can > > really only fail if an allocation fails, in which case everything is > > going bad and we're out of memory. The driver that registers the > > aggregate driver, can succeed at probe and put the attached device on > > the DPM lists before any of the component devices are probed and put on > > the lists. > > > > Within the component device framework this usually isn't that bad > > because the real driver work is done at bind time via > > component{,master}_ops::bind(). It becomes a problem when the driver > > core, or host driver, wants to operate on the component device outside > > of the bind/unbind functions, e.g. via 'remove' or 'shutdown'. The > > driver core doesn't understand the relationship between the host device > > and the component devices and could possibly try to operate on component > > devices when they're already removed from the system or shut down. > > > > Normally, device links or probe defer would reorder the lists and put > > devices that depend on other devices in the lists at the correct > > location, but with component devices this doesn't happen because this > > information isn't expressed anywhere. Drivers simply succeed at > > registering their component or the aggregate driver with the component > > framework and wait for their bind() callback to be called once the other > > components are ready. In summary, the drivers that make up the aggregate > > driver can probe in any order. > > > > This ordering problem becomes fairly obvious when shutting down the > > device with a DSI controller connected to a DSI bridge that is > > controlled via i2c. In this case, the msm display driver wants to tear > > down the display pipeline on shutdown via msm_pdev_shutdown() by calling > > drm_atomic_helper_shutdown(), and it can't do that unless the whole > > display chain is still probed and active in the system. When a display > > bridge is on i2c, the i2c device for the bridge will be created whenever > > the i2c controller probes, which could be before or after the msm > > display driver probes. If the i2c controller probes after the display > > driver, then the i2c controller will be shutdown before the display > > controller during system wide shutdown and thus i2c transactions will > > stop working before the display pipeline is shut down. This means we'll > > have the display bridge trying to access an i2c bus that's shut down > > because drm_atomic_helper_shutdown() is trying to disable the bridge > > after the bridge is off. > > > > The solution is to make the aggregate driver into a real struct driver > > that is bound to a device when the other component devices have all > > probed. Now that the component driver code is a proper bus, we can > > simply register an aggregate driver with that bus via > > component_aggregate_register() and then attach the shutdown hook to that > > driver to be sure that the shutdown for the display pipeline is called > > before any of the component device driver shutdown hooks are called. > > > > Cc: Daniel Vetter > > Cc: "Rafael J. Wysocki" > > Cc: Rob Clark > > Cc: Russell King > > Cc: Saravana Kannan > > Signed-off-by: Stephen Boyd > > --- > > > > As stated in the cover letter, this isn't perfect but it still works. I > > get a warning from runtime PM that the parent device (e00000.mdss) is > > not runtime PM enabled but the child device (the aggregate device) is > > being enabled by the bus logic. I need to move around the place that the > > parent device is runtime PM enabled and probably keep it powered up > > during the entire time that the driver is probed until the aggregate > > driver probes. > > > > drivers/gpu/drm/msm/msm_drv.c | 47 +++++++++++++++++++---------------- > > 1 file changed, 26 insertions(+), 21 deletions(-) > > > > diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c > > index e1104d2454e2..0c64e6a2ce25 100644 > > --- a/drivers/gpu/drm/msm/msm_drv.c > > +++ b/drivers/gpu/drm/msm/msm_drv.c > > @@ -1265,19 +1265,35 @@ static int add_gpu_components(struct device *dev, > > return 0; > > } > > > > -static int msm_drm_bind(struct device *dev) > > +static int msm_drm_bind(struct aggregate_device *adev) > > { > > - return msm_drm_init(dev, &msm_driver); > > + return msm_drm_init(adev->dev.parent, &msm_driver); > > } > > > > -static void msm_drm_unbind(struct device *dev) > > +static void msm_drm_unbind(struct aggregate_device *adev) > > { > > - msm_drm_uninit(dev); > > + msm_drm_uninit(adev->dev.parent); > > +} > > + > > +static void msm_drm_shutdown(struct aggregate_device *adev) > > +{ > > + struct drm_device *drm = platform_get_drvdata(to_platform_device(adev->dev.parent)); > > + struct msm_drm_private *priv = drm ? drm->dev_private : NULL; > > + > > + if (!priv || !priv->kms) > > + return; > > + > > + drm_atomic_helper_shutdown(drm); > > } > > > > -static const struct component_master_ops msm_drm_ops = { > > - .bind = msm_drm_bind, > > - .unbind = msm_drm_unbind, > > +static struct aggregate_driver msm_drm_aggregate_driver = { > > + .probe = msm_drm_bind, > > + .remove = msm_drm_unbind, > > + .shutdown = msm_drm_shutdown, > > + .driver = { > > + .name = "msm_drm", > > + .owner = THIS_MODULE, > > + }, > > }; > > > > /* > > @@ -1306,7 +1322,8 @@ static int msm_pdev_probe(struct platform_device *pdev) > > if (ret) > > goto fail; > > > > - ret = component_master_add_with_match(&pdev->dev, &msm_drm_ops, match); > > + msm_drm_aggregate_driver.match = match; > > This is a bit awkward design, because it means the driver struct can't be > made const, and it will blow up when you have multiple instance of the > same driver. I think the match should stay as part of the register > function call, and be stored in the aggregate_device struct somewhere. > > Otherwise I think this looks really solid and fixes your issue properly. > Obviously needs careful review from Greg KH for the device model side of > things, and from Rafael Wysocki for pm side. > > Bunch of thoughts from a very cursory reading: > > - I think it'd be good if we pass the aggregate_device to all components > when we bind them, plus the void * parameter just to make this less > disruptive. Even more device model goodies. > > - Maybe splatter a pile of sysfs links around so that this all becomes > visible? Could be interesting for debugging ordering issues. Just an > idea, feel free to entirely ignore. Device links give this for free too! You can check what components make up a device and their state too. -Saravana > > - Needs solid kerneldoc for everything exposed to drivers and good > overview DOC: > > - Needs deprecation warnings in the kerneldoc for all the > component_master_* and if feasible with a mechanical conversion, > converting existing users. I'd like to not be stuck with the old model > forever, plus this will give a pile more people to review this code > here. > > Anyway the name changes in probe and remove hooks below are already worth > this on their own imo. That's why I'd like to see them in all drivers. > > Cheers, Daniel > > > + ret = component_aggregate_register(&pdev->dev, &msm_drm_aggregate_driver); > > if (ret) > > goto fail; > > > > @@ -1319,23 +1336,12 @@ static int msm_pdev_probe(struct platform_device *pdev) > > > > static int msm_pdev_remove(struct platform_device *pdev) > > { > > - component_master_del(&pdev->dev, &msm_drm_ops); > > + component_aggregate_unregister(&pdev->dev, &msm_drm_aggregate_driver); > > of_platform_depopulate(&pdev->dev); > > > > return 0; > > } > > > > -static void msm_pdev_shutdown(struct platform_device *pdev) > > -{ > > - struct drm_device *drm = platform_get_drvdata(pdev); > > - struct msm_drm_private *priv = drm ? drm->dev_private : NULL; > > - > > - if (!priv || !priv->kms) > > - return; > > - > > - drm_atomic_helper_shutdown(drm); > > -} > > - > > static const struct of_device_id dt_match[] = { > > { .compatible = "qcom,mdp4", .data = (void *)KMS_MDP4 }, > > { .compatible = "qcom,mdss", .data = (void *)KMS_MDP5 }, > > @@ -1351,7 +1357,6 @@ MODULE_DEVICE_TABLE(of, dt_match); > > static struct platform_driver msm_platform_driver = { > > .probe = msm_pdev_probe, > > .remove = msm_pdev_remove, > > - .shutdown = msm_pdev_shutdown, > > .driver = { > > .name = "msm", > > .of_match_table = dt_match, > > -- > > https://chromeos.dev > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch