mtd: spi-nor: add spi_nor_init() function

This patch extracts some chunks from spi_nor_init_params and spi_nor_scan()
and moves them into a new spi_nor_init() function.

Indeed, spi_nor_init() regroups all the required SPI flash commands to be
sent to the SPI flash memory before performing any runtime operations
(Fast Read, Page Program, Sector Erase, ...). Hence spi_nor_init():
1) removes the flash protection if applicable for certain vendors.
2) sets the Quad Enable bit, if needed, before using Quad SPI protocols.
3) makes the memory enter its (stateful) 4-byte address mode, if needed,
for SPI flash memory > 128Mbits not supporting the 4-byte address
instruction set.

spi_nor_scan() now ends by calling spi_nor_init() once the probe phase has
completed. Further patches could also use spi_nor_init() to implement the
mtd->_resume() handler for the spi-nor framework.

Signed-off-by: Kamal Dasu <[e-mail]>
Signed-off-by: Cyrille Pitchen <[e-mail]>

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

···
 	/* Enable Quad I/O if needed. */
 	enable_quad_io = (spi_nor_get_protocol_width(nor->read_proto) == 4 ||
 			  spi_nor_get_protocol_width(nor->write_proto) == 4);
-	if (enable_quad_io && params->quad_enable) {
-		err = params->quad_enable(nor);
+	if (enable_quad_io && params->quad_enable)
+		nor->quad_enable = params->quad_enable;
+	else
+		nor->quad_enable = NULL;
+
+	return 0;
+}
+
+static int spi_nor_init(struct spi_nor *nor)
+{
+	int err;
+
+	/*
+	 * Atmel, SST, Intel/Numonyx, and others serial NOR tend to power up
+	 * with the software protection bits set
+	 */
+	if (JEDEC_MFR(nor->info) == SNOR_MFR_ATMEL ||
+	    JEDEC_MFR(nor->info) == SNOR_MFR_INTEL ||
+	    JEDEC_MFR(nor->info) == SNOR_MFR_SST ||
+	    nor->info->flags & SPI_NOR_HAS_LOCK) {
+		write_enable(nor);
+		write_sr(nor, 0);
+		spi_nor_wait_till_ready(nor);
+	}
+
+	if (nor->quad_enable) {
+		err = nor->quad_enable(nor);
 		if (err) {
 			dev_err(nor->dev, "quad mode not supported\n");
 			return err;
 		}
 	}
+
+	if ((nor->addr_width == 4) &&
+	    (JEDEC_MFR(nor->info) != SNOR_MFR_SPANSION) &&
+	    !(nor->info->flags & SPI_NOR_4B_OPCODES))
+		set_4byte(nor, nor->info, 1);
 
 	return 0;
 }
···
 	ret = spi_nor_init_params(nor, info, &params);
 	if (ret)
 		return ret;
-
-	/*
-	 * Atmel, SST, Intel/Numonyx, and others serial NOR tend to power up
-	 * with the software protection bits set
-	 */
-
-	if (JEDEC_MFR(info) == SNOR_MFR_ATMEL ||
-	    JEDEC_MFR(info) == SNOR_MFR_INTEL ||
-	    JEDEC_MFR(info) == SNOR_MFR_SST ||
-	    info->flags & SPI_NOR_HAS_LOCK) {
-		write_enable(nor);
-		write_sr(nor, 0);
-		spi_nor_wait_till_ready(nor);
-	}
 
 	if (!mtd->name)
 		mtd->name = dev_name(dev);
···
 		if (JEDEC_MFR(info) == SNOR_MFR_SPANSION ||
 		    info->flags & SPI_NOR_4B_OPCODES)
 			spi_nor_set_4byte_opcodes(nor, info);
-		else
-			set_4byte(nor, info, 1);
 	} else {
 		nor->addr_width = 3;
 	}
···
 		if (ret)
 			return ret;
 	}
+
+	/* Send all the required SPI flash commands to initialize device */
+	nor->info = info;
+	ret = spi_nor_init(nor);
+	if (ret)
+		return ret;
 
 	dev_info(dev, "%s (%lld Kbytes)\n", info->name,
 			(long long)mtd->size >> 10);

include/linux/mtd/spi-nor.h

···
 };
 
 /**
+ * struct flash_info - Forward declaration of a structure used internally by
+ *		       spi_nor_scan()
+ */
+struct flash_info;
+
+/**
  * struct spi_nor - Structure for defining a the SPI NOR layer
  * @mtd:		point to a mtd_info structure
  * @lock:		the lock for the read/write/erase/lock/unlock operations
  * @dev:		point to a spi device, or a spi nor controller device.
+ * @info:		spi-nor part JDEC MFR id and other info
  * @page_size:		the page size of the SPI NOR
  * @addr_width:		number of address bytes
  * @erase_opcode:	the opcode for erasing a sector
···
  * @flash_lock:		[FLASH-SPECIFIC] lock a region of the SPI NOR
  * @flash_unlock:	[FLASH-SPECIFIC] unlock a region of the SPI NOR
  * @flash_is_locked:	[FLASH-SPECIFIC] check if a region of the SPI NOR is
+ * @quad_enable:	[FLASH-SPECIFIC] enables SPI NOR quad mode
  *			completely locked
  * @priv:		the private data
  */
···
 	struct mtd_info		mtd;
 	struct mutex		lock;
 	struct device		*dev;
+	const struct flash_info	*info;
 	u32			page_size;
 	u8			addr_width;
 	u8			erase_opcode;
···
 	int (*flash_lock)(struct spi_nor *nor, loff_t ofs, uint64_t len);
 	int (*flash_unlock)(struct spi_nor *nor, loff_t ofs, uint64_t len);
 	int (*flash_is_locked)(struct spi_nor *nor, loff_t ofs, uint64_t len);
+	int (*quad_enable)(struct spi_nor *nor);
 
 	void *priv;
 };