fpga: microchip-spi: rewrite status polling in a time measurable way

[ Upstream commit 88e705697e801299a13ecaf2ba54599964fe711c ]

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.

While at it, fix polling stop condition to met function's original
intention declared in the comment. The issue with original polling stop
condition is that it stops if any of mask bits is set, while intention
was to stop if all mask bits is set. This was not noticible because only
MPF_STATUS_READY is passed as mask argument and it is BIT(1).

Fixes: 5f8d4a900830 ("fpga: microchip-spi: add Microchip MPF FPGA manager")
Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20221230092922.18822-3-i.bornyakov@metrotek.ru
Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/fpga/microchip-spi.c b/drivers/fpga/microchip-spi.c
index bb69f5b..137fafd 100644 (file)
--- 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)
@@ -194,24 +195,25 @@ static int mpf_ops_parse_header(struct fpga_manager *mgr,
        return 0;
 }
 
-/* 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;
-       }
+       /*
+        * Busy poll HW status. Polling stops if any of the following
+        * conditions are met:
+        *  - timeout is reached
+        *  - mpf_read_status() returns an error
+        *  - busy bit is cleared AND mask bits are set
+        */
+       ret = read_poll_timeout(mpf_read_status, status,
+                               (status < 0) ||
+                               ((status & (MPF_STATUS_BUSY | mask)) == 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)