Merge tag 'regmap-3.4' into regmap-stride

regmap: Last minute bug fix for 3.4

This is a last minute bug fix that was only just noticed since the code
path that's being exercised here is one that is fairly rarely used.  The
changelog for the change itself is extremely clear and the code itself
is obvious to inspection so should be pretty safe.

Conflicts:
	drivers/base/regmap/regmap.c (overlap between the fix and stride code)

1 files changed, 22 insertions, 1 deletions

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index c6db9fb33c4..600060e25ec 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -141,7 +141,7 @@ static inline unsigned __read_seqcount_begin(const seqcount_t *s)
 	unsigned ret;
 
 repeat:
-	ret = s->sequence;
+	ret = ACCESS_ONCE(s->sequence);
 	if (unlikely(ret & 1)) {
 		cpu_relax();
 		goto repeat;
@@ -166,6 +166,27 @@ static inline unsigned read_seqcount_begin(const seqcount_t *s)
 }
 
 /**
+ * raw_seqcount_begin - begin a seq-read critical section
+ * @s: pointer to seqcount_t
+ * Returns: count to be passed to read_seqcount_retry
+ *
+ * raw_seqcount_begin opens a read critical section of the given seqcount.
+ * Validity of the critical section is tested by checking read_seqcount_retry
+ * function.
+ *
+ * Unlike read_seqcount_begin(), this function will not wait for the count
+ * to stabilize. If a writer is active when we begin, we will fail the
+ * read_seqcount_retry() instead of stabilizing at the beginning of the
+ * critical section.
+ */
+static inline unsigned raw_seqcount_begin(const seqcount_t *s)
+{
+	unsigned ret = ACCESS_ONCE(s->sequence);
+	smp_rmb();
+	return ret & ~1;
+}
+
+/**
  * __read_seqcount_retry - end a seq-read critical section (without barrier)
  * @s: pointer to seqcount_t
  * @start: count, from read_seqcount_begin