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

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>

diff --git a/drivers/fpga/microchip-spi.c b/drivers/fpga/microchip-spi.c
index bb69f5beefe783993dd042795300a9047cac22b1..137fafdf57a6fa3450fbaf68b7da67ff8f656a1c 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)