linux-kernel - [PATCH v2 1/2] iopoll: Introduce read_poll_timeout

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Message-Id: <20200424184918.30360-1-kai.heng.feng@canonical.com>
Date:   Sat, 25 Apr 2020 02:49:14 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     yhchuang@...ltek.com, kvalo@...eaurora.org
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        "David S. Miller" <davem@...emloft.net>,
        Dejin Zheng <zhengdejin5@...il.com>,
        Allison Randal <allison@...utok.net>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 1/2] iopoll: Introduce read_poll_timeout_atomic macro

Like read_poll_timeout, an atomic variant for multiple parameter read
function can be useful.

Will be used by a later patch.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
---
v2:
 - Cc linux-wireless.

 include/linux/iopoll.h | 62 +++++++++++++++++++++++++++++-------------
 1 file changed, 43 insertions(+), 19 deletions(-)

diff --git a/include/linux/iopoll.h b/include/linux/iopoll.h
index cb20c733b15a..bc89ac625f26 100644
--- a/include/linux/iopoll.h
+++ b/include/linux/iopoll.h
@@ -57,6 +57,48 @@
 	(cond) ? 0 : -ETIMEDOUT; \
 })
 
+/**
+ * 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; \
+})
+
 /**
  * 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)
@@ -96,25 +138,7 @@
  * macros defined below rather than this macro directly.
  */
 #define readx_poll_timeout_atomic(op, addr, val, cond, delay_us, timeout_us) \
-({ \
-	u64 __timeout_us = (timeout_us); \
-	unsigned long __delay_us = (delay_us); \
-	ktime_t __timeout = ktime_add_us(ktime_get(), __timeout_us); \
-	for (;;) { \
-		(val) = op(addr); \
-		if (cond) \
-			break; \
-		if (__timeout_us && \
-		    ktime_compare(ktime_get(), __timeout) > 0) { \
-			(val) = op(addr); \
-			break; \
-		} \
-		if (__delay_us) \
-			udelay(__delay_us);	\
-	} \
-	(cond) ? 0 : -ETIMEDOUT; \
-})
-
+	read_poll_timeout_atomic(op, val, cond, delay_us, timeout_us, false, addr)
 
 #define readb_poll_timeout(addr, val, cond, delay_us, timeout_us) \
 	readx_poll_timeout(readb, addr, val, cond, delay_us, timeout_us)
-- 
2.17.1