[PATCH 3/7] backports: Add read_poll_timeout{_atomic}()

[Hauke Mehrtens <hauke@hauke-m.de>]

These defines are used by the rtw88 driver.

These defines are copied from Linux commit 5f5323a14cad ("iopoll:
introduce read_poll_timeout macro") and 57a29df34146 ("iopoll: Introduce
read_poll_timeout_atomic macro")

linux/iopoll.h was only added in kernel 4.20, do not include the
original file in older versions.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
---
 backport/backport-include/linux/iopoll.h | 98 ++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 backport/backport-include/linux/iopoll.h

diff --git a/backport/backport-include/linux/iopoll.h b/backport/backport-include/linux/iopoll.h
new file mode 100644
index 00000000..f50187ad
--- /dev/null
+++ b/backport/backport-include/linux/iopoll.h
@@ -0,0 +1,98 @@
+#ifndef _BACKPORTS_LINUX_IOPOLL_H
+#define _BACKPORTS_LINUX_IOPOLL_H 1
+
+#if LINUX_VERSION_IS_GEQ(4,0,0)
+#include_next <linux/iopoll.h>
+#endif
+
+#ifndef read_poll_timeout
+/**
+ * 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; \
+})
+#endif /* read_poll_timeout */
+
+#ifndef read_poll_timeout_atomic
+/**
+ * read_poll_timeout_atomic - Periodically poll an address until a condition is
+ * 				met or a timeout occurs
+ * @op: accessor function (takes @addr as its only argument)
+ * @addr: Address to poll
+ * @val: Variable to read the value into
+ * @cond: Break condition (usually involving @val)
+ * @delay_us: Time to udelay between reads in us (0 tight-loops).  Should
+ *            be less than ~10us since udelay is used (see
+ *            Documentation/timers/timers-howto.rst).
+ * @timeout_us: Timeout in us, 0 means never timeout
+ * @delay_before_read: if it is true, delay @delay_us before read.
+ *
+ * Returns 0 on success and -ETIMEDOUT upon a timeout. In either
+ * case, the last read value at @args is stored in @val.
+ *
+ * When available, you'll probably want to use one of the specialized
+ * macros defined below rather than this macro directly.
+ */
+#define read_poll_timeout_atomic(op, val, cond, delay_us, timeout_us, \
+					delay_before_read, args...) \
+({ \
+	u64 __timeout_us = (timeout_us); \
+	unsigned long __delay_us = (delay_us); \
+	ktime_t __timeout = ktime_add_us(ktime_get(), __timeout_us); \
+	if (delay_before_read && __delay_us) \
+		udelay(__delay_us); \
+	for (;;) { \
+		(val) = op(args); \
+		if (cond) \
+			break; \
+		if (__timeout_us && \
+		    ktime_compare(ktime_get(), __timeout) > 0) { \
+			(val) = op(args); \
+			break; \
+		} \
+		if (__delay_us) \
+			udelay(__delay_us); \
+	} \
+	(cond) ? 0 : -ETIMEDOUT; \
+})
+#endif /* read_poll_timeout_atomic */
+
+#endif /* _BACKPORTS_LINUX_IOPOLL_H */
-- 
2.20.1

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