From patchwork Wed Mar 27 09:50:25 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ulf Hansson X-Patchwork-Id: 2349061 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork1.kernel.org Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by patchwork1.kernel.org (Postfix) with ESMTP id 41BB53FC8C for ; Wed, 27 Mar 2013 09:54:28 +0000 (UTC) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UKn1V-0000rT-Ma; Wed, 27 Mar 2013 09:52:01 +0000 Received: from eu1sys200aog105.obsmtp.com ([207.126.144.119]) by merlin.infradead.org with smtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1UKn0O-0000U2-7w for linux-arm-kernel@lists.infradead.org; Wed, 27 Mar 2013 09:50:53 +0000 Received: from beta.dmz-ap.st.com ([138.198.100.35]) (using TLSv1) by eu1sys200aob105.postini.com ([207.126.147.11]) with SMTP ID DSNKUVLA8oXGDpU8fJWbqdcpXPCXgKs6Zeur@postini.com; Wed, 27 Mar 2013 09:50:51 UTC Received: from zeta.dmz-ap.st.com (ns6.st.com [138.198.234.13]) by beta.dmz-ap.st.com (STMicroelectronics) with ESMTP id 51D0D119; Wed, 27 Mar 2013 09:42:32 +0000 (GMT) Received: from relay1.stm.gmessaging.net (unknown [10.230.100.17]) by zeta.dmz-ap.st.com (STMicroelectronics) with ESMTP id C17FDEC1; Wed, 27 Mar 2013 09:50:38 +0000 (GMT) Received: from exdcvycastm004.EQ1STM.local (alteon-source-exch [10.230.100.61]) (using TLSv1 with cipher RC4-MD5 (128/128 bits)) (Client CN "exdcvycastm004", Issuer "exdcvycastm004" (not verified)) by relay1.stm.gmessaging.net (Postfix) with ESMTPS id CE0B524C07C; Wed, 27 Mar 2013 10:50:32 +0100 (CET) Received: from steludxu1397.lud.stericsson.com (10.230.100.153) by smtp.stericsson.com (10.230.100.2) with Microsoft SMTP Server (TLS) id 8.3.279.5; Wed, 27 Mar 2013 10:50:37 +0100 From: Ulf Hansson To: , Mike Turquette Subject: [PATCH V3 3/3] clk: Fixup locking issues for clk_set_parent Date: Wed, 27 Mar 2013 10:50:25 +0100 Message-ID: <1364377825-6171-4-git-send-email-ulf.hansson@stericsson.com> X-Mailer: git-send-email 1.7.10 In-Reply-To: <1364377825-6171-1-git-send-email-ulf.hansson@stericsson.com> References: <1364377825-6171-1-git-send-email-ulf.hansson@stericsson.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130327_055052_551436_897AEE8D X-CRM114-Status: GOOD ( 17.24 ) X-Spam-Score: -4.2 (----) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-4.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [207.126.144.119 listed in list.dnswl.org] -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: Linus Walleij , Ulf Hansson , Par-Olof Hakansson X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: Ulf Hansson Updating the clock tree topology must be protected with the spinlock when doing clk_set_parent, otherwise we can not handle the migration of the enable_count in a safe manner. While issuing the .set_parent callback to make the clk-hw perform the switch to the new parent, we can not hold the spinlock since it is must be allowed to be slow path. This complicates error handling, but is still possible to achieve. Signed-off-by: Ulf Hansson --- drivers/clk/clk.c | 67 +++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 52 insertions(+), 15 deletions(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 6fa301b..90dcbd5 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1300,31 +1300,71 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent, u8 p_index) unsigned long flags; int ret = 0; struct clk *old_parent = clk->parent; + bool migrated_enable = false; - /* migrate prepare and enable */ + /* migrate prepare */ if (clk->prepare_count) __clk_prepare(parent); - /* FIXME replace with clk_is_enabled(clk) someday */ spin_lock_irqsave(&enable_lock, flags); - if (clk->enable_count) + + /* migrate enable */ + if (clk->enable_count) { __clk_enable(parent); + migrated_enable = true; + } + + /* update the clk tree topology */ + clk_reparent(clk, parent); + spin_unlock_irqrestore(&enable_lock, flags); /* change clock input source */ if (parent && clk->ops->set_parent) ret = clk->ops->set_parent(clk->hw, p_index); - /* clean up old prepare and enable */ - spin_lock_irqsave(&enable_lock, flags); - if (clk->enable_count) + if (ret) { + /* + * The error handling is tricky due to that we need to release + * the spinlock while issuing the .set_parent callback. This + * means the new parent might have been enabled/disabled in + * between, which must be considered when doing rollback. + */ + spin_lock_irqsave(&enable_lock, flags); + + clk_reparent(clk, old_parent); + + if (migrated_enable && clk->enable_count) { + __clk_disable(parent); + } else if (migrated_enable && (clk->enable_count == 0)) { + __clk_disable(old_parent); + } else if (!migrated_enable && clk->enable_count) { + __clk_disable(parent); + __clk_enable(old_parent); + } + + spin_unlock_irqrestore(&enable_lock, flags); + + if (clk->prepare_count) + __clk_unprepare(parent); + + return ret; + } + + /* clean up enable for old parent if migration was done */ + if (migrated_enable) { + spin_lock_irqsave(&enable_lock, flags); __clk_disable(old_parent); - spin_unlock_irqrestore(&enable_lock, flags); + spin_unlock_irqrestore(&enable_lock, flags); + } + /* clean up prepare for old parent if migration was done */ if (clk->prepare_count) __clk_unprepare(old_parent); - return ret; + /* update debugfs with new clk tree topology */ + clk_debug_reparent(clk, parent); + return 0; } /** @@ -1387,14 +1427,11 @@ int clk_set_parent(struct clk *clk, struct clk *parent) /* do the re-parent */ ret = __clk_set_parent(clk, parent, p_index); - /* propagate ABORT_RATE_CHANGE if .set_parent failed */ - if (ret) { + /* propagate rate recalculation accordingly */ + if (ret) __clk_recalc_rates(clk, ABORT_RATE_CHANGE); - goto out; - } - - /* propagate rate recalculation downstream */ - __clk_reparent(clk, parent); + else + __clk_recalc_rates(clk, POST_RATE_CHANGE); out: mutex_unlock(&prepare_lock);