wilc1000: changes for SPI communication stall issue found with Iperf

Added retry mechanism to ensure VMM enable bit is set during the
block transfer of data between host and WILC FW.
Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201208103739.28597-1-ajay.kathat@microchip.com

drivers/net/wireless/microchip/wilc1000/spi.c

@@ -35,6 +35,7 @@ static const struct wilc_hif_func wilc_hif_spi;
 #define CMD_SINGLE_READ				0xca
 #define CMD_RESET				0xcf
 
+#define SPI_ENABLE_VMM_RETRY_LIMIT		2
 #define DATA_PKT_SZ_256				256
 #define DATA_PKT_SZ_512				512
 #define DATA_PKT_SZ_1K				1024
@@ -856,8 +857,26 @@ static int wilc_spi_read_int(struct wilc *wilc, u32 *int_status)
 
 static int wilc_spi_clear_int_ext(struct wilc *wilc, u32 val)
 {
-	return spi_internal_write(wilc, WILC_SPI_INT_CLEAR - WILC_SPI_REG_BASE,
-				  val);
+	int ret;
+	int retry = SPI_ENABLE_VMM_RETRY_LIMIT;
+	u32 check;
+
+	while (retry) {
+		ret = spi_internal_write(wilc,
+					 WILC_SPI_INT_CLEAR - WILC_SPI_REG_BASE,
+					 val);
+		if (ret)
+			break;
+
+		ret = spi_internal_read(wilc,
+					WILC_SPI_INT_CLEAR - WILC_SPI_REG_BASE,
+					&check);
+		if (ret || ((check & EN_VMM) == (val & EN_VMM)))
+			break;
+
+		retry--;
+	}
+	return ret;
 }
 
 static int wilc_spi_sync_ext(struct wilc *wilc, int nint)