[PATCH AUTOSEL 5.6 30/38] i2c: tegra: Better handle case where CPU0 is busy for a long time

Sasha Levin
2020-04-24T12:31:38Z

From: Dmitry Osipenko <digetx@gmail.com>

[ Upstream commit a900aeac253729411cf33c6cb598c152e9e4137f ]

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 <digetx@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 cbc2ad49043e4..0daa863fb26f2 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;
--
2.20.1