mtd: spi-nor: Parse SFDP SCCR Map

Parse just the 22nd dword and look for the 'DTR Octal Mode Enable
Volatile bit'.

SPI_NOR_IO_MODE_EN_VOLATILE should be set just for the flashes
that don't define the optional SFDP SCCR Map. For the others,
let the SFDP do its job and fill the SNOR_F_IO_MODE_EN_VOLATILE
flag. We avoid this way polluting the flash flags when declaring
one.
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20201005153138.6437-10-p.yadav@ti.com

drivers/mtd/spi-nor/sfdp.c

@@ -21,6 +21,10 @@
 #define SFDP_SECTOR_MAP_ID	0xff81	/* Sector Map Table */
 #define SFDP_4BAIT_ID		0xff84  /* 4-byte Address Instruction Table */
 #define SFDP_PROFILE1_ID	0xff05	/* xSPI Profile 1.0 table. */
+#define SFDP_SCCR_MAP_ID	0xff87	/*
+					 * Status, Control and Configuration
+					 * Register Map.
+					 */
 
 #define SFDP_SIGNATURE		0x50444653U
 
@@ -1195,6 +1199,46 @@ static int spi_nor_parse_profile1(struct spi_nor *nor,
 	return ret;
 }
 
+#define SCCR_DWORD22_OCTAL_DTR_EN_VOLATILE		BIT(31)
+
+/**
+ * spi_nor_parse_sccr() - Parse the Status, Control and Configuration Register
+ *                        Map.
+ * @nor:		pointer to a 'struct spi_nor'
+ * @sccr_header:	pointer to the 'struct sfdp_parameter_header' describing
+ *			the SCCR Map table length and version.
+ * @params:		pointer to the 'struct spi_nor_flash_parameter' to be.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spi_nor_parse_sccr(struct spi_nor *nor,
+			      const struct sfdp_parameter_header *sccr_header,
+			      struct spi_nor_flash_parameter *params)
+{
+	u32 *dwords, addr;
+	size_t len;
+	int ret;
+
+	len = sccr_header->length * sizeof(*dwords);
+	dwords = kmalloc(len, GFP_KERNEL);
+	if (!dwords)
+		return -ENOMEM;
+
+	addr = SFDP_PARAM_HEADER_PTP(sccr_header);
+	ret = spi_nor_read_sfdp(nor, addr, len, dwords);
+	if (ret)
+		goto out;
+
+	le32_to_cpu_array(dwords, sccr_header->length);
+
+	if (FIELD_GET(SCCR_DWORD22_OCTAL_DTR_EN_VOLATILE, dwords[22]))
+		nor->flags |= SNOR_F_IO_MODE_EN_VOLATILE;
+
+out:
+	kfree(dwords);
+	return ret;
+}
+
 /**
  * spi_nor_parse_sfdp() - parse the Serial Flash Discoverable Parameters.
  * @nor:		pointer to a 'struct spi_nor'
@@ -1300,6 +1344,10 @@ int spi_nor_parse_sfdp(struct spi_nor *nor,
 			err = spi_nor_parse_profile1(nor, param_header, params);
 			break;
 
+		case SFDP_SCCR_MAP_ID:
+			err = spi_nor_parse_sccr(nor, param_header, params);
+			break;
+
 		default:
 			break;
 		}