mtd: spi-nor: micron-st: Skip FSR reading if SPI controller does not support it

The Intel SPI controller does not support low level operations, like
reading the flag status register (FSR). It only exposes a set of high
level operations for software to use. For this reason check the return
value of micron_st_nor_read_fsr() and if the operation was not
supported, use the status register value only. This allows the chip to
work even when attached to Intel SPI controller (there are such systems
out there).
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20220506105158.43613-1-mika.westerberg@linux.intel.com

drivers/mtd/spi-nor/micron-st.c

@@ -399,8 +399,16 @@ static int micron_st_nor_ready(struct spi_nor *nor)
 		return sr_ready;
 
 	ret = micron_st_nor_read_fsr(nor, nor->bouncebuf);
-	if (ret)
-		return ret;
+	if (ret) {
+		/*
+		 * Some controllers, such as Intel SPI, do not support low
+		 * level operations such as reading the flag status
+		 * register. They only expose small amount of high level
+		 * operations to the software. If this is the case we use
+		 * only the status register value.
+		 */
+		return ret == -EOPNOTSUPP ? sr_ready : ret;
+	}
 
 	if (nor->bouncebuf[0] & (FSR_E_ERR | FSR_P_ERR)) {
 		if (nor->bouncebuf[0] & FSR_E_ERR)