From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753457AbbAUQNK (ORCPT ); Wed, 21 Jan 2015 11:13:10 -0500 Received: from mail-pa0-f44.google.com ([209.85.220.44]:39468 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752449AbbAUQNF (ORCPT ); Wed, 21 Jan 2015 11:13:05 -0500 From: Thierry Reding To: dri-devel@lists.freedesktop.org Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, Russell King , Mike Turquette , Stephen Boyd Subject: [PATCH v2] clk: Introduce clk_has_parent() Date: Wed, 21 Jan 2015 17:13:00 +0100 Message-Id: <1421856780-32103-1-git-send-email-thierry.reding@gmail.com> X-Mailer: git-send-email 2.1.3 In-Reply-To: <1421750935-4023-2-git-send-email-thierry.reding@gmail.com> References: <1421750935-4023-2-git-send-email-thierry.reding@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thierry Reding This new function is similar to clk_set_parent(), except that it doesn't actually change the parent. It merely checks that the given parent clock can be a parent for the given clock. A situation where this is useful is to check that a particular setup is valid before switching to it. One specific use-case for this is atomic modesetting in the DRM framework where setting a mode is divided into a check phase where a given configuration is validated before applying changes to the hardware. Cc: Russell King Cc: Mike Turquette Cc: Stephen Boyd Signed-off-by: Thierry Reding --- Changes in v2: - lookup parent name in parent names array and make function lockless - rename function from clk_try_parent() to clk_has_parent() - return boolean drivers/clk/clk.c | 30 ++++++++++++++++++++++++++++++ include/linux/clk.h | 17 +++++++++++++++++ 2 files changed, 47 insertions(+) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index af06b7377d37..470266297dea 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1672,6 +1672,36 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent) } /** + * clk_has_parent - check if a clock is a possible parent for another + * @clk: clock source + * @parent: parent clock source + * + * This function can be used in drivers that need to check that a clock can be + * the parent of another without actually changing the parent. + * + * Returns true if @parent is a possible parent for @clk, false otherwise. + */ +bool clk_has_parent(struct clk *clk, struct clk *parent) +{ + unsigned int i; + + /* NULL clocks should be nops, so return success if either is NULL. */ + if (!clk || !parent) + return true; + + /* Optimize for the case where the parent is already the parent. */ + if (clk->parent == parent) + return true; + + for (i = 0; i < clk->num_parents; i++) + if (strcmp(clk->parent_names[i], parent->name) == 0) + return true; + + return false; +} +EXPORT_SYMBOL_GPL(clk_has_parent); + +/** * clk_set_parent - switch the parent of a mux clk * @clk: the mux clk whose input we are switching * @parent: the new input to clk diff --git a/include/linux/clk.h b/include/linux/clk.h index fb1ac65f127c..df28673be2a1 100644 --- a/include/linux/clk.h +++ b/include/linux/clk.h @@ -328,6 +328,18 @@ long clk_round_rate(struct clk *clk, unsigned long rate); int clk_set_rate(struct clk *clk, unsigned long rate); /** + * clk_has_parent - check if a clock is a possible parent for another + * @clk: clock source + * @parent: parent clock source + * + * This function can be used in drivers that need to check that a clock can be + * the parent of another without actually changing the parent. + * + * Returns true if @parent is a possible parent for @clk, false otherwise. + */ +bool clk_has_parent(struct clk *clk, struct clk *parent); + +/** * clk_set_parent - set the parent clock source for this clock * @clk: clock source * @parent: parent clock source @@ -400,6 +412,11 @@ static inline long clk_round_rate(struct clk *clk, unsigned long rate) return 0; } +static inline bool clk_has_parent(struct clk *clk, struct clk *parent) +{ + return true; +} + static inline int clk_set_parent(struct clk *clk, struct clk *parent) { return 0; -- 2.1.3