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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 C2428C432C3 for ; Sun, 7 Mar 2021 17:08:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9817D65107 for ; Sun, 7 Mar 2021 17:08:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232582AbhCGRIX (ORCPT ); Sun, 7 Mar 2021 12:08:23 -0500 Received: from aposti.net ([89.234.176.197]:40130 "EHLO aposti.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232563AbhCGRIC (ORCPT ); Sun, 7 Mar 2021 12:08:02 -0500 From: Paul Cercueil To: Michael Turquette , Stephen Boyd , Ulf Hansson , Russell King Cc: od@zcrc.me, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-mmc@vger.kernel.org, Paul Cercueil Subject: [PATCH 1/2] clk: Add clk_get_first_to_set_rate Date: Sun, 7 Mar 2021 17:07:41 +0000 Message-Id: <20210307170742.70949-2-paul@crapouillou.net> In-Reply-To: <20210307170742.70949-1-paul@crapouillou.net> References: <20210307170742.70949-1-paul@crapouillou.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The purpose of this function is to be used along with the notifier mechanism. When a parent clock can see its rate externally changed at any moment, and a driver needs a specific clock rate to function, it can register a notifier on the parent clock, and call clk_set_rate() on the base clock to adjust its frequency according to the new parent clock. This works fine, until the base clock has the CLK_SET_RATE_PARENT flag set. In that case, calling clk_set_rate() on the base clock will call clk_set_rate() on the parent clock, which will trigger the notifier again, and we're in a loop. For that reason, we need to register the notifier on the parent clock of the first ancestor of the base clock that will effectively modify its rate when clk_set_rate() is called, which we can now obtain with clk_get_first_to_set_rate(). Signed-off-by: Paul Cercueil --- drivers/clk/clk.c | 9 +++++++++ include/linux/clk.h | 16 ++++++++++++++++ 2 files changed, 25 insertions(+) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 5052541a0986..3fd75e283482 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -2450,6 +2450,15 @@ struct clk *clk_get_parent(struct clk *clk) } EXPORT_SYMBOL_GPL(clk_get_parent); +struct clk *clk_get_first_to_set_rate(struct clk *clk) +{ + while (clk && (clk->core->flags & CLK_SET_RATE_PARENT)) + clk = clk_get_parent(clk); + + return clk; +} + + static struct clk_core *__clk_init_parent(struct clk_core *core) { u8 index = 0; diff --git a/include/linux/clk.h b/include/linux/clk.h index 266e8de3cb51..f0ea6ac6aa39 100644 --- a/include/linux/clk.h +++ b/include/linux/clk.h @@ -766,6 +766,17 @@ struct clk *clk_get_parent(struct clk *clk); */ struct clk *clk_get_sys(const char *dev_id, const char *con_id); +/** + * clk_get_first_to_set_rate - get a pointer to the clock that will + * effectively modify its rate when clk_set_rate(clk) is called + * (might be clk itself, or any ancestor) + * @clk: clock source + * + * Returns struct clk corresponding to the matched clock source, or + * NULL on error. + */ +struct clk *clk_get_first_to_set_rate(struct clk *clk); + /** * clk_save_context - save clock context for poweroff * @@ -928,6 +939,11 @@ static inline struct clk *clk_get_parent(struct clk *clk) return NULL; } +static inline struct clk *clk_get_first_to_set_rate(struct clk *clk) +{ + return NULL; +} + static inline struct clk *clk_get_sys(const char *dev_id, const char *con_id) { return NULL; -- 2.30.1