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Subject[PATCH] regmap: add iopoll-like polling macro
Date
This patch adds a macro regmap_read_poll_timeout that works similar
to the readx_poll_timeout defined in linux/iopoll.h, except that this
can also return the error value returned by a failed regmap_read.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
include/linux/regmap.h | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)

diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 3dc08ce..26914df 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -95,6 +95,45 @@ struct reg_sequence {
#define regmap_fields_force_update_bits(field, id, mask, val) \
regmap_fields_update_bits_base(field, id, mask, val, NULL, false, true)

+/**
+ * regmap_read_poll_timeout - Poll until a condition is met or a timeout occurs
+ * @map: Regmap to read from
+ * @addr: Address to poll
+ * @val: Unsigned integer 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.txt).
+ * @timeout_us: Timeout in us, 0 means never timeout
+ *
+ * Returns 0 on success and -ETIMEDOUT upon a timeout or the regmap_read
+ * error return value in case of a error read. In the two former cases,
+ * 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.
+ *
+ * This is modelled after the readx_poll_timeout macros in linux/iopoll.h.
+ */
+#define regmap_read_poll_timeout(map, addr, val, cond, sleep_us, timeout_us) \
+({ \
+ ktime_t timeout = ktime_add_us(ktime_get(), timeout_us); \
+ int ret; \
+ might_sleep_if(sleep_us); \
+ for (;;) { \
+ ret = regmap_read((map), (addr), &(val)); \
+ if (ret) \
+ break; \
+ if (cond) \
+ break; \
+ if (timeout_us && ktime_compare(ktime_get(), timeout) > 0) { \
+ ret = regmap_read((map), (addr), &(val)); \
+ break; \
+ } \
+ if (sleep_us) \
+ usleep_range((sleep_us >> 2) + 1, sleep_us); \
+ } \
+ ret ?: ((cond) ? 0 : -ETIMEDOUT); \
+})
+
#ifdef CONFIG_REGMAP

enum regmap_endian {
--
2.8.1
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