[PATCH v2 2/3] fpga: microchip-spi: rewrite status polling in a time measurable way

[Ivan Bornyakov <i.bornyakov@metrotek.ru>]

Original busy loop with retries count in mpf_poll_status() is not too
reliable, as it takes different times on different systems. Replace it
with read_poll_timeout() macro.

Fixes: 5f8d4a900830 ("fpga: microchip-spi: add Microchip MPF FPGA manager")
Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
---
 drivers/fpga/microchip-spi.c | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/drivers/fpga/microchip-spi.c b/drivers/fpga/microchip-spi.c
index e72fedd93a27..f3ddfab87499 100644
--- a/drivers/fpga/microchip-spi.c
+++ b/drivers/fpga/microchip-spi.c
@@ -6,6 +6,7 @@
 #include <asm/unaligned.h>
 #include <linux/delay.h>
 #include <linux/fpga/fpga-mgr.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/spi/spi.h>
@@ -33,7 +34,7 @@
 
 #define	MPF_BITS_PER_COMPONENT_SIZE	22
 
-#define	MPF_STATUS_POLL_RETRIES		10000
+#define	MPF_STATUS_POLL_TIMEOUT		(2 * USEC_PER_SEC)
 #define	MPF_STATUS_BUSY			BIT(0)
 #define	MPF_STATUS_READY		BIT(1)
 #define	MPF_STATUS_SPI_VIOLATION	BIT(2)
@@ -197,21 +198,17 @@ static int mpf_ops_parse_header(struct fpga_manager *mgr,
 /* Poll HW status until busy bit is cleared and mask bits are set. */
 static int mpf_poll_status(struct mpf_priv *priv, u8 mask)
 {
-	int status, retries = MPF_STATUS_POLL_RETRIES;
+	int ret, status;
 
-	while (retries--) {
-		status = mpf_read_status(priv);
-		if (status < 0)
-			return status;
-
-		if (status & MPF_STATUS_BUSY)
-			continue;
-
-		if (!mask || (status & mask))
-			return status;
-	}
+	ret = read_poll_timeout(mpf_read_status, status,
+				(status < 0) ||
+				(!(status & MPF_STATUS_BUSY) &&
+				 (!mask || (status & mask))),
+				0, MPF_STATUS_POLL_TIMEOUT, false, priv);
+	if (ret < 0)
+		return ret;
 
-	return -EBUSY;
+	return status;
 }
 
 static int mpf_spi_write(struct mpf_priv *priv, const void *buf, size_t buf_size)
-- 
2.38.2