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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT autolearn=ham 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 2C379C43381 for ; Mon, 1 Apr 2019 17:26:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EA7E32133D for ; Mon, 1 Apr 2019 17:26:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554139615; bh=91Q69tv/y/KTKzi/Yhn2f6ZmuBZZ6TSTkqo4L+xxjPY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=vHaa7dFD88hNRkRtW1cFTAnlMuim8nS/1KdRI1tDcXpagYYsXcnlxjR7adkhYWKMh /klsKs0UwLXBcFOptT1ZJpHtLGbQy2vk2N+pwqRZU42k4j9Yk11CuU6qvHnpU84TcO QWJ2RQ8zbgyzfUbtEXeyHtCUU40ufNRnJwysZ/G8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732601AbfDAR0x (ORCPT ); Mon, 1 Apr 2019 13:26:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:59260 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728810AbfDAR0v (ORCPT ); Mon, 1 Apr 2019 13:26:51 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 961BC20856; Mon, 1 Apr 2019 17:26:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554139611; bh=91Q69tv/y/KTKzi/Yhn2f6ZmuBZZ6TSTkqo4L+xxjPY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=z2qIENlfFXN9ujq++ieiig7YXZRBff4WOSeeVvIZRlZZ7ZqK/YPmnb35goj3IBSG+ ARfAomdYN/xd2OVucEXc+AeMorTM0PvSFqOaZs3k9ejrUnZIcU0RStnOs2Pj1b1sBo yZUrB7m6QnFz0shT7LDfaHf+zibO15IC1B0Dqp10= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kohji Okuno , Shawn Guo Subject: [PATCH 4.9 19/56] ARM: imx6q: cpuidle: fix bug that CPU might not wake up at expected time Date: Mon, 1 Apr 2019 19:02:35 +0200 Message-Id: <20190401170104.859505425@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190401170103.398401360@linuxfoundation.org> References: <20190401170103.398401360@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kohji Okuno commit 91740fc8242b4f260cfa4d4536d8551804777fae upstream. In the current cpuidle implementation for i.MX6q, the CPU that sets 'WAIT_UNCLOCKED' and the CPU that returns to 'WAIT_CLOCKED' are always the same. While the CPU that sets 'WAIT_UNCLOCKED' is in IDLE state of "WAIT", if the other CPU wakes up and enters IDLE state of "WFI" istead of "WAIT", this CPU can not wake up at expired time. Because, in the case of "WFI", the CPU must be waked up by the local timer interrupt. But, while 'WAIT_UNCLOCKED' is set, the local timer is stopped, when all CPUs execute "wfi" instruction. As a result, the local timer interrupt is not fired. In this situation, this CPU will wake up by IRQ different from local timer. (e.g. broacast timer) So, this fix changes CPU to return to 'WAIT_CLOCKED'. Signed-off-by: Kohji Okuno Fixes: e5f9dec8ff5f ("ARM: imx6q: support WAIT mode using cpuidle") Cc: Signed-off-by: Shawn Guo Signed-off-by: Greg Kroah-Hartman --- arch/arm/mach-imx/cpuidle-imx6q.c | 27 ++++++++++----------------- 1 file changed, 10 insertions(+), 17 deletions(-) --- a/arch/arm/mach-imx/cpuidle-imx6q.c +++ b/arch/arm/mach-imx/cpuidle-imx6q.c @@ -16,30 +16,23 @@ #include "cpuidle.h" #include "hardware.h" -static atomic_t master = ATOMIC_INIT(0); -static DEFINE_SPINLOCK(master_lock); +static int num_idle_cpus = 0; +static DEFINE_SPINLOCK(cpuidle_lock); static int imx6q_enter_wait(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { - if (atomic_inc_return(&master) == num_online_cpus()) { - /* - * With this lock, we prevent other cpu to exit and enter - * this function again and become the master. - */ - if (!spin_trylock(&master_lock)) - goto idle; + spin_lock(&cpuidle_lock); + if (++num_idle_cpus == num_online_cpus()) imx6_set_lpm(WAIT_UNCLOCKED); - cpu_do_idle(); - imx6_set_lpm(WAIT_CLOCKED); - spin_unlock(&master_lock); - goto done; - } + spin_unlock(&cpuidle_lock); -idle: cpu_do_idle(); -done: - atomic_dec(&master); + + spin_lock(&cpuidle_lock); + if (num_idle_cpus-- == num_online_cpus()) + imx6_set_lpm(WAIT_CLOCKED); + spin_unlock(&cpuidle_lock); return index; }