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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 8E08DC76190 for ; Mon, 22 Jul 2019 23:47:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5AB0C2199C for ; Mon, 22 Jul 2019 23:47:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="FSrDP0k+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731863AbfGVXrz (ORCPT ); Mon, 22 Jul 2019 19:47:55 -0400 Received: from mail-ot1-f66.google.com ([209.85.210.66]:45944 "EHLO mail-ot1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731929AbfGVXrw (ORCPT ); Mon, 22 Jul 2019 19:47:52 -0400 Received: by mail-ot1-f66.google.com with SMTP id x21so3695810otq.12 for ; Mon, 22 Jul 2019 16:47:51 -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=ezUTQcxWaNEMctu/WrThORHFyr5A9yxp6lNSMDh1t/w=; b=FSrDP0k+ApVeqUbXOrsC6ZZewwi5kfyxz5zNEVEP+0ZEsSwIkmwNLONlkCeSgkl5wo gSPZPtSMUAGS4bvHBrY+UUDKLk2PRbk+gvGc3CP1jnlOU6H9SzxesUPgD9b41rakxkzF 9221m+qOc2IllOk8cSlLlxSK+1Qp8oBcoyiHBMGKkhgA6FCL15+rKrAENStZXmCzBf8g G+Wl/79jKjvYm3Rl+RwW41s6lokTH/MuU7N6HQGcj1a4L275MrQrXfkSPOo1cHjKY6qx iIFdrDLUYgAkT7xjD8sfvfqDhXFMSCNWnHphsfNo5TnZ6FgrRxHvVxtvGk4g27BRICfK 70ZQ== 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=ezUTQcxWaNEMctu/WrThORHFyr5A9yxp6lNSMDh1t/w=; b=iXMSV/LU/xPjvc2CGz73+N1KXMWjwljFep3XkVeQa5+G+ltaoE7UUVjHnYfI+xOccq z/PBgLX2lVozsY65kBtAfh5eRQM7ITnDlDtv3xeGM66/SssUe2B16dMVx2geCVL/Hhc8 M7Suv9RzCBvANrAmuUvfobi7J9HCq/uk62QivU+L7wW0rGOgc5wEOCe1z4bWu0Y7PzmK FJXjptIWYRRFqxVV2SHOoAo7fPCwrje5g8acNq4Jy4/uVclQfeh/QBnDW3Rm3ySMsASj PZG1pMaisNonh/YOyR4Eyffy7isf7KhsLIIQQwW1cumn/C9u0A/jUPCGO0QtX00JXEbC leZw== X-Gm-Message-State: APjAAAUpZ+crB5GCkI9XpgnDwxhrOtqg4nZua+UyHOW9Fj/yuOCCxO1y 7NqQbfkjrE7iQOV21BhIqvtNzNUUqduWq8ylhI5I7A== X-Google-Smtp-Source: APXvYqwh/Kq2TD4k37U9oU8MKp9SSQGgVZ+B0WGSNY0ozl/ONS8huqU9oJWQ0jLXhXRxfuftmSHpEfd1Pu46pr6k/yQ= X-Received: by 2002:a05:6830:160c:: with SMTP id g12mr18026255otr.231.1563839271203; Mon, 22 Jul 2019 16:47:51 -0700 (PDT) MIME-Version: 1.0 References: <20190720061647.234852-1-saravanak@google.com> In-Reply-To: <20190720061647.234852-1-saravanak@google.com> From: Saravana Kannan Date: Mon, 22 Jul 2019 16:47:15 -0700 Message-ID: Subject: Re: [PATCH v6 0/7] Solve postboot supplier cleanup and optimize probe ordering To: Rob Herring , Mark Rutland , Greg Kroah-Hartman , "Rafael J. Wysocki" , Frank Rowand Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , LKML , David Collins , Android Kernel Team Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 19, 2019 at 11:16 PM Saravana Kannan wrote: > > Add device-links to track functional dependencies between devices > after they are created (but before they are probed) by looking at > their common DT bindings like clocks, interconnects, etc. > > Having functional dependencies automatically added before the devices > are probed, provides the following benefits: > > - Optimizes device probe order and avoids the useless work of > attempting probes of devices that will not probe successfully > (because their suppliers aren't present or haven't probed yet). > > For example, in a commonly available mobile SoC, registering just > one consumer device's driver at an initcall level earlier than the > supplier device's driver causes 11 failed probe attempts before the > consumer device probes successfully. This was with a kernel with all > the drivers statically compiled in. This problem gets a lot worse if > all the drivers are loaded as modules without direct symbol > dependencies. > > - Supplier devices like clock providers, interconnect providers, etc > need to keep the resources they provide active and at a particular > state(s) during boot up even if their current set of consumers don't > request the resource to be active. This is because the rest of the > consumers might not have probed yet and turning off the resource > before all the consumers have probed could lead to a hang or > undesired user experience. > > Some frameworks (Eg: regulator) handle this today by turning off > "unused" resources at late_initcall_sync and hoping all the devices > have probed by then. This is not a valid assumption for systems with > loadable modules. Other frameworks (Eg: clock) just don't handle > this due to the lack of a clear signal for when they can turn off > resources. This leads to downstream hacks to handle cases like this > that can easily be solved in the upstream kernel. > > By linking devices before they are probed, we give suppliers a clear > count of the number of dependent consumers. Once all of the > consumers are active, the suppliers can turn off the unused > resources without making assumptions about the number of consumers. > > By default we just add device-links to track "driver presence" (probe > succeeded) of the supplier device. If any other functionality provided > by device-links are needed, it is left to the consumer/supplier > devices to change the link when they probe. > > v1 -> v2: > - Drop patch to speed up of_find_device_by_node() > - Drop depends-on property and use existing bindings > > v2 -> v3: > - Refactor the code to have driver core initiate the linking of devs > - Have driver core link consumers to supplier before it's probed > - Add support for drivers to edit the device links before probing > > v3 -> v4: > - Tested edit_links() on system with cyclic dependency. Works. > - Added some checks to make sure device link isn't attempted from > parent device node to child device node. > - Added way to pause/resume sync_state callbacks across > of_platform_populate(). > - Recursively parse DT node to create device links from parent to > suppliers of parent and all child nodes. > > v4 -> v5: > - Fixed copy-pasta bugs with linked list handling > - Walk up the phandle reference till I find an actual device (needed > for regulators to work) > - Added support for linking devices from regulator DT bindings > - Tested the whole series again to make sure cyclic dependencies are > broken with edit_links() and regulator links are created properly. > > v5 -> v6: > - Split, squashed and reordered some of the patches. > - Refactored the device linking code to follow the same code pattern for > any property. > > I've also not updated this patch series to handle the new patch [1] from > Rafael. Will do that once this patch series is close to being Acked. > > [1] - https://lore.kernel.org/lkml/3121545.4lOhFoIcdQ@kreacher/ > > -Saravana > > > Saravana Kannan (7): > driver core: Add support for linking devices during device addition > driver core: Add edit_links() callback for drivers > of/platform: Add functional dependency link from DT bindings > driver core: Add sync_state driver/bus callback > of/platform: Pause/resume sync state during init and > of_platform_populate() > of/platform: Create device links for all child-supplier depencencies > of/platform: Don't create device links for default busses > > .../admin-guide/kernel-parameters.txt | 5 + > drivers/base/core.c | 168 ++++++++++++++++ > drivers/base/dd.c | 29 +++ > drivers/of/platform.c | 182 ++++++++++++++++++ > include/linux/device.h | 47 +++++ > 5 files changed, 431 insertions(+) Update: Tested this refactor on hardware by backporting to a 4.14 kernel. Works just as it did before the refactor. Also, nudge to make sure this series isn't lost over the weekend email snooze. -Saravana From mboxrd@z Thu Jan 1 00:00:00 1970 From: Saravana Kannan Subject: Re: [PATCH v6 0/7] Solve postboot supplier cleanup and optimize probe ordering Date: Mon, 22 Jul 2019 16:47:15 -0700 Message-ID: References: <20190720061647.234852-1-saravanak@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20190720061647.234852-1-saravanak@google.com> Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring , Mark Rutland , Greg Kroah-Hartman , "Rafael J. Wysocki" , Frank Rowand Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , LKML , David Collins , Android Kernel Team List-Id: devicetree@vger.kernel.org On Fri, Jul 19, 2019 at 11:16 PM Saravana Kannan wrote: > > Add device-links to track functional dependencies between devices > after they are created (but before they are probed) by looking at > their common DT bindings like clocks, interconnects, etc. > > Having functional dependencies automatically added before the devices > are probed, provides the following benefits: > > - Optimizes device probe order and avoids the useless work of > attempting probes of devices that will not probe successfully > (because their suppliers aren't present or haven't probed yet). > > For example, in a commonly available mobile SoC, registering just > one consumer device's driver at an initcall level earlier than the > supplier device's driver causes 11 failed probe attempts before the > consumer device probes successfully. This was with a kernel with all > the drivers statically compiled in. This problem gets a lot worse if > all the drivers are loaded as modules without direct symbol > dependencies. > > - Supplier devices like clock providers, interconnect providers, etc > need to keep the resources they provide active and at a particular > state(s) during boot up even if their current set of consumers don't > request the resource to be active. This is because the rest of the > consumers might not have probed yet and turning off the resource > before all the consumers have probed could lead to a hang or > undesired user experience. > > Some frameworks (Eg: regulator) handle this today by turning off > "unused" resources at late_initcall_sync and hoping all the devices > have probed by then. This is not a valid assumption for systems with > loadable modules. Other frameworks (Eg: clock) just don't handle > this due to the lack of a clear signal for when they can turn off > resources. This leads to downstream hacks to handle cases like this > that can easily be solved in the upstream kernel. > > By linking devices before they are probed, we give suppliers a clear > count of the number of dependent consumers. Once all of the > consumers are active, the suppliers can turn off the unused > resources without making assumptions about the number of consumers. > > By default we just add device-links to track "driver presence" (probe > succeeded) of the supplier device. If any other functionality provided > by device-links are needed, it is left to the consumer/supplier > devices to change the link when they probe. > > v1 -> v2: > - Drop patch to speed up of_find_device_by_node() > - Drop depends-on property and use existing bindings > > v2 -> v3: > - Refactor the code to have driver core initiate the linking of devs > - Have driver core link consumers to supplier before it's probed > - Add support for drivers to edit the device links before probing > > v3 -> v4: > - Tested edit_links() on system with cyclic dependency. Works. > - Added some checks to make sure device link isn't attempted from > parent device node to child device node. > - Added way to pause/resume sync_state callbacks across > of_platform_populate(). > - Recursively parse DT node to create device links from parent to > suppliers of parent and all child nodes. > > v4 -> v5: > - Fixed copy-pasta bugs with linked list handling > - Walk up the phandle reference till I find an actual device (needed > for regulators to work) > - Added support for linking devices from regulator DT bindings > - Tested the whole series again to make sure cyclic dependencies are > broken with edit_links() and regulator links are created properly. > > v5 -> v6: > - Split, squashed and reordered some of the patches. > - Refactored the device linking code to follow the same code pattern for > any property. > > I've also not updated this patch series to handle the new patch [1] from > Rafael. Will do that once this patch series is close to being Acked. > > [1] - https://lore.kernel.org/lkml/3121545.4lOhFoIcdQ@kreacher/ > > -Saravana > > > Saravana Kannan (7): > driver core: Add support for linking devices during device addition > driver core: Add edit_links() callback for drivers > of/platform: Add functional dependency link from DT bindings > driver core: Add sync_state driver/bus callback > of/platform: Pause/resume sync state during init and > of_platform_populate() > of/platform: Create device links for all child-supplier depencencies > of/platform: Don't create device links for default busses > > .../admin-guide/kernel-parameters.txt | 5 + > drivers/base/core.c | 168 ++++++++++++++++ > drivers/base/dd.c | 29 +++ > drivers/of/platform.c | 182 ++++++++++++++++++ > include/linux/device.h | 47 +++++ > 5 files changed, 431 insertions(+) Update: Tested this refactor on hardware by backporting to a 4.14 kernel. Works just as it did before the refactor. Also, nudge to make sure this series isn't lost over the weekend email snooze. -Saravana