i2c: tegra: Better handle case where CPU0 is busy for a long time

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: Thierry Reding <treding@nvidia.com>

drivers/i2c/busses/i2c-tegra.c

@@ -996,14 +996,13 @@ 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)) {
+		if (completion_done(complete)) {
-				s64 delta = ktime_ms_delta(ktimeout, ktime);
+			s64 delta = ktime_ms_delta(ktimeout, ktime);
 
-				return msecs_to_jiffies(delta) ?: 1;
+			return msecs_to_jiffies(delta) ?: 1;
-			}
 		}
 
 		ktime = ktime_get();
@@ -1030,14 +1029,18 @@ 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
+		 * Under some rare circumstances (like running KASAN +
-		 * synchronization, which is done by disable_irq().
+		 * 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)) {
+		if (ret == 0)
-			dev_warn(i2c_dev->dev,
+			ret = tegra_i2c_poll_completion_timeout(i2c_dev,
-				 "completion done after timeout\n");
+								complete, 0);
-			ret = 1;
-		}
 	}
 
 	return ret;