From patchwork Fri Jul 12 23:52:33 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Saravana Kannan X-Patchwork-Id: 1131534 Return-Path: X-Original-To: incoming-dt@patchwork.ozlabs.org Delivered-To: patchwork-incoming-dt@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=devicetree-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.b="sZfogWVp"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45lqVY0RMxz9sNF for ; Sat, 13 Jul 2019 09:52:53 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728468AbfGLXwu (ORCPT ); Fri, 12 Jul 2019 19:52:50 -0400 Received: from mail-pg1-f201.google.com ([209.85.215.201]:35393 "EHLO mail-pg1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728451AbfGLXwu (ORCPT ); Fri, 12 Jul 2019 19:52:50 -0400 Received: by mail-pg1-f201.google.com with SMTP id c18so6617778pgk.2 for ; Fri, 12 Jul 2019 16:52:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=kubhLUQUEQ+MMlDaxxhREyfqUccCsBdmf65YIfZuyiU=; b=sZfogWVpl0WupSgXxobwPVgtqFYb8RoRRma3OwBoaxhRXn57Dp+oMlhhpkTesNxiqu rh5btlSMmGgrlpXdS8vINrZ+PoA++Y8u9UQu9GHf/Vh+5LBb6Se5KSzMPFB3hFAdZhVh zDN/3cU7eFXUd/Wlnl4VSbBF4Dbr++txX+9q56pXTPHHMo1PlG0bxbxWLsxZmt1eMPgK C15UAqLlhU22gPHx+YSnnhR8rbEmoEEgu34+Wf30ejxvtU2G6wUw/62xOqQUW2m17qz4 RffQtmoHceXFzW2yPwRn8SPk1UiP3uiUlWYiZ5fuTuV+oDY1vS/YHiRRFJYh73zAzxx8 lgvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=kubhLUQUEQ+MMlDaxxhREyfqUccCsBdmf65YIfZuyiU=; b=FN+ECba6ekrXPOERPQl4tazhUXqG2D3zgTQWGUEneTXrHV7MhYIZT2akvLGbqS/Mw4 EjB90Kc9hI0xaasx7Pxhmb2Ofqaf81kXxuj8zBMX4UrGud6NTWWq+o8jcMD5p8Kmv93F s8Kc1o8aURRptlkcu9AO3dYtXu6sKlZ4qjRO+sxX+Em7cRD4mAuMblz+UVQG1wsH+Opc LITJj+b0FUiQGlJ2F/acKkXo/GTeLVNIJp6XzaXnfwSvLJdFEVTOzB2bFUlss6wQrCLh Eg2Z/T8hUQYCgPAO8LAgcS2OlqdW+u27E/qhnA23cdN5VgI0maDqJq2w1suyt3Sox4az QW6w== X-Gm-Message-State: APjAAAVjH1iDDN+zGiU4z/qKN/uf7VBacDxqHm3uE4fLZhQuahTcCkOo gZd/ctWVmoybk1l7NTxN+Ei76HcwDWCSrSc= X-Google-Smtp-Source: APXvYqyLvGuZNnM67TcwOHOvl29k6lf0GENmWIwfnemtAT0jfPDGWFKhSQwbTQ0RHkdaGTQE2XWNaazjxmOyKkg= X-Received: by 2002:a63:e213:: with SMTP id q19mr13928383pgh.180.1562975569235; Fri, 12 Jul 2019 16:52:49 -0700 (PDT) Date: Fri, 12 Jul 2019 16:52:33 -0700 Message-Id: <20190712235245.202558-1-saravanak@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog Subject: [PATCH v5 00/11] Solve postboot supplier cleanup and optimize probe ordering From: Saravana Kannan To: Rob Herring , Mark Rutland , Greg Kroah-Hartman , "Rafael J. Wysocki" , Frank Rowand Cc: Saravana Kannan , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, David Collins , kernel-team@android.com Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 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. I could probably squash some of the patches, but leaving them like this because I think it's easier to understand this way. 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 (11): driver core: Add support for linking devices during device addition of/platform: Add functional dependency link from DT bindings driver core: Add sync_state driver/bus callback driver core: Add edit_links() callback for drivers driver core: Add APIs to pause/resume sync state callbacks of/platform: Pause/resume sync state in of_platform_populate() of/platform: Sanity check DT bindings before creating device links of/platform: Make sure supplier DT node is device when creating device links of/platform: Create device links for all child-supplier depencencies of/platform: Add functional dependency link from DT regulator bindings of/platform: Don't create device links default busses .../admin-guide/kernel-parameters.txt | 5 + drivers/base/core.c | 168 ++++++++++++++++++ drivers/base/dd.c | 29 +++ drivers/of/platform.c | 132 ++++++++++++++ include/linux/device.h | 47 +++++ 5 files changed, 381 insertions(+)