From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:60814 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752795AbcEAXVW (ORCPT ); Sun, 1 May 2016 19:21:22 -0400 Subject: Patch "i2c: exynos5: Fix possible ABBA deadlock by keeping I2C clock prepared" has been added to the 4.4-stable tree To: javier@osg.samsung.com Cc: , From: Date: Sun, 01 May 2016 16:21:20 -0700 Message-ID: <146214488010114@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled i2c: exynos5: Fix possible ABBA deadlock by keeping I2C clock prepared to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: i2c-exynos5-fix-possible-abba-deadlock-by-keeping-i2c-clock-prepared.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 10ff4c5239a137abfc896ec73ef3d15a0f86a16a Mon Sep 17 00:00:00 2001 From: Javier Martinez Canillas Date: Sat, 16 Apr 2016 21:14:52 -0400 Subject: i2c: exynos5: Fix possible ABBA deadlock by keeping I2C clock prepared From: Javier Martinez Canillas commit 10ff4c5239a137abfc896ec73ef3d15a0f86a16a upstream. The exynos5 I2C controller driver always prepares and enables a clock before using it and then disables unprepares it when the clock is not used anymore. But this can cause a possible ABBA deadlock in some scenarios since a driver that uses regmap to access its I2C registers, will first grab the regmap lock and then the I2C xfer function will grab the prepare lock when preparing the I2C clock. But since the clock driver also uses regmap for I2C accesses, preparing a clock will first grab the prepare lock and then the regmap lock when using the regmap API. An example of this happens on the Exynos5422 Odroid XU4 board where a s2mps11 PMIC is used and both the s2mps11 regulators and clk drivers share the same I2C regmap. The possible deadlock is reported by the kernel lockdep: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sec_core:428:(regmap)->lock); lock(prepare_lock); lock(sec_core:428:(regmap)->lock); lock(prepare_lock); *** DEADLOCK *** Fix it by leaving the code prepared on probe and use {en,dis}able in the I2C transfer function. This patch is similar to commit 34e81ad5f0b6 ("i2c: s3c2410: fix ABBA deadlock by keeping clock prepared") that fixes the same bug in other driver for an I2C controller found in Samsung SoCs. Reported-by: Anand Moon Signed-off-by: Javier Martinez Canillas Reviewed-by: Anand Moon Reviewed-by: Krzysztof Kozlowski Signed-off-by: Wolfram Sang Signed-off-by: Greg Kroah-Hartman --- drivers/i2c/busses/i2c-exynos5.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) --- a/drivers/i2c/busses/i2c-exynos5.c +++ b/drivers/i2c/busses/i2c-exynos5.c @@ -671,7 +671,9 @@ static int exynos5_i2c_xfer(struct i2c_a return -EIO; } - clk_prepare_enable(i2c->clk); + ret = clk_enable(i2c->clk); + if (ret) + return ret; for (i = 0; i < num; i++, msgs++) { stop = (i == num - 1); @@ -695,7 +697,7 @@ static int exynos5_i2c_xfer(struct i2c_a } out: - clk_disable_unprepare(i2c->clk); + clk_disable(i2c->clk); return ret; } @@ -747,7 +749,9 @@ static int exynos5_i2c_probe(struct plat return -ENOENT; } - clk_prepare_enable(i2c->clk); + ret = clk_prepare_enable(i2c->clk); + if (ret) + return ret; mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); i2c->regs = devm_ioremap_resource(&pdev->dev, mem); @@ -799,6 +803,10 @@ static int exynos5_i2c_probe(struct plat platform_set_drvdata(pdev, i2c); + clk_disable(i2c->clk); + + return 0; + err_clk: clk_disable_unprepare(i2c->clk); return ret; @@ -810,6 +818,8 @@ static int exynos5_i2c_remove(struct pla i2c_del_adapter(&i2c->adap); + clk_unprepare(i2c->clk); + return 0; } @@ -821,6 +831,8 @@ static int exynos5_i2c_suspend_noirq(str i2c->suspended = 1; + clk_unprepare(i2c->clk); + return 0; } @@ -830,7 +842,9 @@ static int exynos5_i2c_resume_noirq(stru struct exynos5_i2c *i2c = platform_get_drvdata(pdev); int ret = 0; - clk_prepare_enable(i2c->clk); + ret = clk_prepare_enable(i2c->clk); + if (ret) + return ret; ret = exynos5_hsi2c_clock_setup(i2c); if (ret) { @@ -839,7 +853,7 @@ static int exynos5_i2c_resume_noirq(stru } exynos5_i2c_init(i2c); - clk_disable_unprepare(i2c->clk); + clk_disable(i2c->clk); i2c->suspended = 0; return 0; Patches currently in stable-queue which might be from javier@osg.samsung.com are queue-4.4/i2c-exynos5-fix-possible-abba-deadlock-by-keeping-i2c-clock-prepared.patch