---

yaml
---
r: 225763
b: refs/heads/master
c: 7decaa5
h: refs/heads/master
i:
  225761: 33aaf44
  225759: 1b8c3d6
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: fd3ee6d3421bc05ce42ee7f48071aee72051af28
+refs/heads/master: 7decaa557a20f48aabef35f817ec16ef563567b0

trunk/drivers/rtc/rtc-sa1100.c

@@ -117,7 +117,23 @@ static irqreturn_t sa1100_rtc_interrupt(int irq, void *dev_id)
 	rtsr = RTSR;
 	/* clear interrupt sources */
 	RTSR = 0;
-	RTSR = (RTSR_AL | RTSR_HZ) & (rtsr >> 2);
+	/* Fix for a nasty initialization problem the in SA11xx RTSR register.
+	 * See also the comments in sa1100_rtc_probe(). */
+	if (rtsr & (RTSR_ALE | RTSR_HZE)) {
+		/* This is the original code, before there was the if test
+		 * above. This code does not clear interrupts that were not
+		 * enabled. */
+		RTSR = (RTSR_AL | RTSR_HZ) & (rtsr >> 2);
+	} else {
+		/* For some reason, it is possible to enter this routine
+		 * without interruptions enabled, it has been tested with
+		 * several units (Bug in SA11xx chip?).
+		 *
+		 * This situation leads to an infinite "loop" of interrupt
+		 * routine calling and as a result the processor seems to
+		 * lock on its first call to open(). */
+		RTSR = RTSR_AL | RTSR_HZ;
+	}
 
 	/* clear alarm interrupt if it has occurred */
 	if (rtsr & RTSR_AL)
@@ -382,6 +398,30 @@ static int sa1100_rtc_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, rtc);
 
+	/* Fix for a nasty initialization problem the in SA11xx RTSR register.
+	 * See also the comments in sa1100_rtc_interrupt().
+	 *
+	 * Sometimes bit 1 of the RTSR (RTSR_HZ) will wake up 1, which means an
+	 * interrupt pending, even though interrupts were never enabled.
+	 * In this case, this bit it must be reset before enabling
+	 * interruptions to avoid a nonexistent interrupt to occur.
+	 *
+	 * In principle, the same problem would apply to bit 0, although it has
+	 * never been observed to happen.
+	 *
+	 * This issue is addressed both here and in sa1100_rtc_interrupt().
+	 * If the issue is not addressed here, in the times when the processor
+	 * wakes up with the bit set there will be one spurious interrupt.
+	 *
+	 * The issue is also dealt with in sa1100_rtc_interrupt() to be on the
+	 * safe side, once the condition that lead to this strange
+	 * initialization is unknown and could in principle happen during
+	 * normal processing.
+	 *
+	 * Notice that clearing bit 1 and 0 is accomplished by writting ONES to
+	 * the corresponding bits in RTSR. */
+	RTSR = RTSR_AL | RTSR_HZ;
+
 	return 0;
 }