[PATCH v3 1/2] iopoll: Introduce memory-mapped IO polling macros

[Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

From: Matt Wagantall <mattw-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>

It is sometimes necessary to poll a memory-mapped register until its
value satisfies some condition. Introduce a family of convenience macros
that do this. Tight-loop and sleeping versions are provided with and
without timeouts.

Cc: Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Signed-off-by: Matt Wagantall <mattw-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
Signed-off-by: Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
---
 include/linux/iopoll.h | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 include/linux/iopoll.h

diff --git a/include/linux/iopoll.h b/include/linux/iopoll.h
new file mode 100644
index 0000000000..594b0d4f03
--- /dev/null
+++ b/include/linux/iopoll.h
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2012-2014 The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _LINUX_IOPOLL_H
+#define _LINUX_IOPOLL_H
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/hrtimer.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/io.h>
+
+/**
+ * readl_poll_timeout - Periodically poll an address until a condition is met or a timeout occurs
+ * @addr: Address to poll
+ * @val: Variable to read the value into
+ * @cond: Break condition (usually involving @val)
+ * @sleep_us: Maximum time to sleep between reads in us (0 tight-loops)
+ * @timeout_us: Timeout in us, 0 means never timeout
+ *
+ * Returns 0 on success and -ETIMEDOUT upon a timeout. In either
+ * case, the last read value at @addr is stored in @val. Must not
+ * be called from atomic context if sleep_us or timeout_us are used.
+ */
+#define readl_poll_timeout(addr, val, cond, sleep_us, timeout_us) \
+({ \
+	ktime_t timeout = ktime_add_us(ktime_get(), timeout_us); \
+	might_sleep_if(timeout_us); \
+	for (;;) { \
+		(val) = readl(addr); \
+		if (cond) \
+			break; \
+		if (timeout_us && ktime_compare(ktime_get(), timeout) > 0) { \
+			(val) = readl(addr); \
+			break; \
+		} \
+		if (sleep_us) \
+			usleep_range(DIV_ROUND_UP(sleep_us, 4), sleep_us); \
+	} \
+	(cond) ? 0 : -ETIMEDOUT; \
+})
+
+/**
+ * readl_poll_timeout_atomic - Periodically poll an address until a condition is met or a timeout occurs
+ * @addr: Address to poll
+ * @val: Variable to read the value into
+ * @cond: Break condition (usually involving @val)
+ * @max_reads: Maximum number of reads before giving up
+ * @time_between_us: Time to udelay() between successive reads
+ *
+ * Returns 0 on success and -ETIMEDOUT upon a timeout.
+ */
+#define readl_poll_timeout_atomic(addr, val, cond, max_reads, time_between_us) \
+({ \
+	int count; \
+	for (count = (max_reads); count > 0; count--) { \
+		(val) = readl(addr); \
+		if (cond) \
+			break; \
+		udelay(time_between_us); \
+	} \
+	(cond) ? 0 : -ETIMEDOUT; \
+})
+
+#endif /* _LINUX_IOPOLL_H */
-- 
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