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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT 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 C7E80C04EBF for ; Tue, 4 Dec 2018 19:25:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 877F62082B for ; Tue, 4 Dec 2018 19:25:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 877F62082B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-clk-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726043AbeLDTY4 (ORCPT ); Tue, 4 Dec 2018 14:24:56 -0500 Received: from mail.bootlin.com ([62.4.15.54]:47409 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725831AbeLDTYz (ORCPT ); Tue, 4 Dec 2018 14:24:55 -0500 Received: by mail.bootlin.com (Postfix, from userid 110) id 6DF1020A35; Tue, 4 Dec 2018 20:24:52 +0100 (CET) Received: from localhost.localdomain (unknown [91.224.148.103]) by mail.bootlin.com (Postfix) with ESMTPSA id 9C7682074D; Tue, 4 Dec 2018 20:24:41 +0100 (CET) From: Miquel Raynal To: Michael Turquette , Stephen Boyd , Russell King Cc: linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Thomas Petazzoni , Antoine Tenart , Maxime Chevallier , Gregory Clement , Nadav Haklai , Miquel Raynal Subject: [PATCH v3 0/4] Add device links to clocks Date: Tue, 4 Dec 2018 20:24:36 +0100 Message-Id: <20181204192440.12125-1-miquel.raynal@bootlin.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-clk-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-clk@vger.kernel.org Hello, While working on suspend to RAM feature, I ran into troubles multiple times when clocks where not suspending/resuming at the desired time. I had a look at the core and I think the same logic as in the regulator's core may be applied here to (very easily) fix this issue: using device links. The only additional change I had to do was to always (when available) populate the device entry of the core clock structure so that it could be used later. This is the purpose of patch 1. Patch 2 actually adds support for device links. Here is a step-by-step explanation of how links are managed, following Maxime Ripard's suggestion. The order of probe has no importance because the framework already handles orphaned clocks so let's be simple and say there are two root clocks, not depending on anything, that are probed first: xtal0 and xtal1. None of these clocks have a parent, there is no device link in the game, yet. +----------------+ +----------------+ | | | | | | | | | xtal0 core | | xtal1 core | | | | | | | | | +-------^^-------+ +-------^^-------+ || || || || +----------------+ +----------------+ | | | | | xtal0 clk | | xtal1 clk | | | | | +----------------+ +----------------+ Then, a peripheral clock periph0 is probed. His parent is xtal1. The clock_register_*() call will run __clk_init_parent() and a link between periph0's core and xtal1's core will be created and stored in periph0's core->parent_clk_link entry. +----------------+ +----------------+ | | | | | | | | | xtal0 core | | xtal1 core | | | | | | | | | +-------^^-------+ +-------^^-------+ || || || || +----------------+ +----------------+ | | | | | xtal0 clk | | xtal1 clk | | | | | +----------------+ +-------^--------+ | | +--------------+ | ->parent_clk_link | +----------------+ | | | | | periph0 core | | | | | +-------^^-------+ || || +----------------+ | | | periph0 clk 0 | | | +----------------+ Then, device0 is probed and "get" the periph0 clock. clk_get() will be called and a struct clk will be instantiated for device0 (called in the figure clk 1). A link between device0 and the new clk 1 instance of periph0 will be created and stored in the clk->consumer_link entry. +----------------+ +----------------+ | | | | | | | | | xtal0 core | | xtal1 core | | | | | | | | | +-------^^-------+ +-------^^-------+ || || || || +----------------+ +----------------+ | | | | | xtal0 clk | | xtal1 clk | | | | | +----------------+ +-------^--------+ | | +--------------+ | ->parent_clk_link | +----------------+ | | | | | periph0 core | | <-------------+ | <-------------| +-------^^-------+ || || || || || +----------------+ +----------------+ | | | | | periph0 clk 0 | | periph0 clk 1 | | | | | +----------------+ +----------------+ | | ->consumer_link | | | +-------v--------+ | device0 | +----------------+ Right now, device0 is linked to periph0, itself linked to xtal1 so everything is fine. Now let's get some fun: the new parent of periph0 is xtal1. The process will call clk_reparent(), periph0's core->parent_clk_link will be destroyed and a new link to xtal1 will be setup and stored. The situation is now that device0 is linked to periph0 and periph0 is linked to xtal1, so the dependency between device0 and xtal1 is still clear. +----------------+ +----------------+ | | | | | | | | | xtal0 core | | xtal1 core | | | | | | | | | +-------^^-------+ +-------^^-------+ || || || || +----------------+ +----------------+ | | | | | xtal0 clk | | xtal1 clk | | | | | +-------^--------+ +----------------+ | | \ / +----------------------------x ->parent_clk_link | / \ | +----------------+ | | | | | periph0 core | | <-------------+ | <-------------| +-------^^-------+ || || || || || +----------------+ +----------------+ | | | | | periph0 clk 0 | | periph0 clk 1 | | | | | +----------------+ +----------------+ | | ->consumer_link | | | +-------v--------+ | device0 | +----------------+ I assume periph0 cannot be removed while there are devices using it, same for xtal0. What can happen is that device0 'put' the clock periph0. The relevant link is deleted and the clk instance dropped. +----------------+ +----------------+ | | | | | | | | | xtal0 core | | xtal1 core | | | | | | | | | +-------^^-------+ +-------^^-------+ || || || || +----------------+ +----------------+ | | | | | xtal0 clk | | xtal1 clk | | | | | +-------^--------+ +----------------+ | | \ / +----------------------------x ->parent_clk_link | / \ | +----------------+ | | | | | periph0 core | | | | | +-------^^-------+ || || +----------------+ | | | periph0 clk 0 | | | +----------------+ Now we can unregister periph0: link with the parent will be destroyed and the clock may be safely removed. +----------------+ +----------------+ | | | | | | | | | xtal0 core | | xtal1 core | | | | | | | | | +-------^^-------+ +-------^^-------+ || || || || +----------------+ +----------------+ | | | | | xtal0 clk | | xtal1 clk | | | | | +----------------+ +----------------+ This is my understanding of the common clock framework and how links can be added to it. As a result, here are the links created during the boot of an ESPRESSObin: ----->8----- marvell-armada-3700-tbg-clock d0013200.tbg: Linked as a consumer to d0013800.pinctrl:xtal-clk marvell-armada-3700-tbg-clock d0013200.tbg: Dropping the link to d0013800.pinctrl:xtal-clk marvell-armada-3700-tbg-clock d0013200.tbg: Linked as a consumer to d0013800.pinctrl:xtal-clk marvell-armada-3700-periph-clock d0013000.nb-periph-clk: Linked as a consumer to d0013200.tbg marvell-armada-3700-periph-clock d0013000.nb-periph-clk: Linked as a consumer to d0013800.pinctrl:xtal-clk marvell-armada-3700-periph-clock d0018000.sb-periph-clk: Linked as a consumer to d0013200.tbg mvneta d0030000.ethernet: Linked as a consumer to d0018000.sb-periph-clk xhci-hcd d0058000.usb: Linked as a consumer to d0018000.sb-periph-clk xenon-sdhci d00d0000.sdhci: Linked as a consumer to d0013000.nb-periph-clk xenon-sdhci d00d0000.sdhci: Dropping the link to d0013000.nb-periph-clk mvebu-uart d0012000.serial: Linked as a consumer to d0013800.pinctrl:xtal-clk advk-pcie d0070000.pcie: Linked as a consumer to d0018000.sb-periph-clk xenon-sdhci d00d0000.sdhci: Linked as a consumer to d0013000.nb-periph-clk xenon-sdhci d00d0000.sdhci: Linked as a consumer to regulator.1 cpu cpu0: Linked as a consumer to d0013000.nb-periph-clk cpu cpu0: Dropping the link to d0013000.nb-periph-clk cpu cpu0: Linked as a consumer to d0013000.nb-periph-clk -----8<----- Thanks, Miquèl Changes since v2: ================= * Fixed compilation issue when not using the common clock framework: removed the static keyword in front of clk_link/unlink_consumer() dummy definitions in clkdev.c. Changes since v1: ================= * Add clock->clock links, not only device->clock links. * Helpers renamed: > clk_{link,unlink}_hierarchy() > clk_{link,unlink}_consumer() * Add two patches to pass a "struct device" to the clock registration helper. This way device links may work between clocks themselves (otherwise the link is not created). Miquel Raynal (4): clk: core: clarify the check for runtime PM clk: core: link consumer with clock driver clk: mvebu: armada-37xx-tbg: fill the device entry when registering the clocks clk: mvebu: armada-37xx-xtal: fill the device entry when registering the clock drivers/clk/clk.c | 64 ++++++++++++++++++++++++---- drivers/clk/clkdev.c | 16 +++++-- drivers/clk/mvebu/armada-37xx-tbg.c | 6 ++- drivers/clk/mvebu/armada-37xx-xtal.c | 3 +- include/linux/clk-provider.h | 2 + 5 files changed, 77 insertions(+), 14 deletions(-) -- 2.19.1