From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: [PATCH v2 1/2] i2c: tegra: Better handle case where CPU0 is busy for a long time Date: Tue, 24 Mar 2020 22:12:16 +0300 Message-ID: <20200324191217.1829-2-digetx@gmail.com> References: <20200324191217.1829-1-digetx@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: Received: from mail-lj1-f196.google.com ([209.85.208.196]:38859 "EHLO mail-lj1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727747AbgCXTN3 (ORCPT ); Tue, 24 Mar 2020 15:13:29 -0400 In-Reply-To: <20200324191217.1829-1-digetx@gmail.com> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Thierry Reding , Jonathan Hunter , Laxman Dewangan , Wolfram Sang Cc: linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org Boot CPU0 always handle I2C interrupt and under some rare circumstances (like running KASAN + NFS root) it may stuck in uninterruptible state for a significant time. In this case we will get timeout if I2C transfer is running on a sibling CPU, despite of IRQ being raised. In order to handle this rare condition, the IRQ status needs to be checked after completion timeout. Signed-off-by: Dmitry Osipenko --- drivers/i2c/busses/i2c-tegra.c | 27 +++++++++++++++------------ 1 file changed, 15 insertions(+), 12 deletions(-) diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index cbc2ad49043e..0daa863fb26f 100644 --- a/drivers/i2c/busses/i2c-tegra.c +++ b/drivers/i2c/busses/i2c-tegra.c @@ -1000,14 +1000,13 @@ tegra_i2c_poll_completion_timeout(struct tegra_i2c_dev *i2c_dev, do { u32 status = i2c_readl(i2c_dev, I2C_INT_STATUS); - if (status) { + if (status) tegra_i2c_isr(i2c_dev->irq, i2c_dev); - if (completion_done(complete)) { - s64 delta = ktime_ms_delta(ktimeout, ktime); + if (completion_done(complete)) { + s64 delta = ktime_ms_delta(ktimeout, ktime); - return msecs_to_jiffies(delta) ?: 1; - } + return msecs_to_jiffies(delta) ?: 1; } ktime = ktime_get(); @@ -1034,14 +1033,18 @@ tegra_i2c_wait_completion_timeout(struct tegra_i2c_dev *i2c_dev, disable_irq(i2c_dev->irq); /* - * There is a chance that completion may happen after IRQ - * synchronization, which is done by disable_irq(). + * Under some rare circumstances (like running KASAN + + * NFS root) CPU, which handles interrupt, may stuck in + * uninterruptible state for a significant time. In this + * case we will get timeout if I2C transfer is running on + * a sibling CPU, despite of IRQ being raised. + * + * In order to handle this rare condition, the IRQ status + * needs to be checked after timeout. */ - if (ret == 0 && completion_done(complete)) { - dev_warn(i2c_dev->dev, - "completion done after timeout\n"); - ret = 1; - } + if (ret == 0) + ret = tegra_i2c_poll_completion_timeout(i2c_dev, + complete, 0); } return ret; -- 2.25.1