From: Dejin Zheng <zhengdejin5@gmail.com>
Date: Mon, 23 Mar 2020 23:05:51 +0800
Subject: iopoll: introduce read_poll_timeout macro

Git-commit: 5f5323a14cad19323060a8cbf9d96f2280a462dd
Patch-mainline: v5.7-rc1
References: git-fixes

this macro is an extension of readx_poll_timeout macro. the accessor
function op just supports only one parameter in the readx_poll_timeout
macro, but this macro can supports multiple variable parameters for
it. so functions like phy_read(struct phy_device *phydev, u32 regnum)
and phy_read_mmd(struct phy_device *phydev, int devad, u32 regnum) can
also use this poll timeout core. and also expand it can sleep some time
before read operation.

Signed-off-by: Dejin Zheng <zhengdejin5@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 include/linux/iopoll.h | 44 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/include/linux/iopoll.h b/include/linux/iopoll.h
index 35e15dfd4155..70f89b389648 100644
--- a/include/linux/iopoll.h
+++ b/include/linux/iopoll.h
@@ -13,6 +13,50 @@
 #include <linux/errno.h>
 #include <linux/io.h>
 
+/**
+ * read_poll_timeout - Periodically poll an address until a condition is
+ *			met or a timeout occurs
+ * @op: accessor function (takes @args as its arguments)
+ * @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).  Should be less than ~20ms since usleep_range
+ *            is used (see Documentation/timers/timers-howto.rst).
+ * @timeout_us: Timeout in us, 0 means never timeout
+ * @sleep_before_read: if it is true, sleep @sleep_us before read.
+ * @args: arguments for @op poll
+ *
+ * Returns 0 on success and -ETIMEDOUT upon a timeout. In either
+ * case, the last read value at @args is stored in @val. Must not
+ * be called from atomic context if sleep_us or timeout_us are used.
+ *
+ * When available, you'll probably want to use one of the specialized
+ * macros defined below rather than this macro directly.
+ */
+#define read_poll_timeout(op, val, cond, sleep_us, timeout_us, \
+				sleep_before_read, args...) \
+({ \
+	u64 __timeout_us = (timeout_us); \
+	unsigned long __sleep_us = (sleep_us); \
+	ktime_t __timeout = ktime_add_us(ktime_get(), __timeout_us); \
+	might_sleep_if((__sleep_us) != 0); \
+	if (sleep_before_read && __sleep_us) \
+		usleep_range((__sleep_us >> 2) + 1, __sleep_us); \
+	for (;;) { \
+		(val) = op(args); \
+		if (cond) \
+			break; \
+		if (__timeout_us && \
+		    ktime_compare(ktime_get(), __timeout) > 0) { \
+			(val) = op(args); \
+			break; \
+		} \
+		if (__sleep_us) \
+			usleep_range((__sleep_us >> 2) + 1, __sleep_us); \
+	} \
+	(cond) ? 0 : -ETIMEDOUT; \
+})
+
 /**
  * readx_poll_timeout - Periodically poll an address until a condition is met or a timeout occurs
  * @op: accessor function (takes @addr as its only argument)
-- 
2.26.2