From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Date: Wed, 6 Dec 2017 10:53:41 +0800
Subject: mtd: spi-nor: add an API to restore the status of SPI flash chip

Git-commit: 8dee1d971af9af2f7b5f54c2eac4ebd04c5c237c
Patch-mainline: v4.16-rc1
References: fate#326572

Add this API to restore the status of SPI flash chip to the default
such as addressing mode, whenever detach the driver from device or
reboot the system.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
 Documentation/mtd/spi-nor.txt |    3 +++
 drivers/mtd/spi-nor/spi-nor.c |   10 ++++++++++
 include/linux/mtd/spi-nor.h   |    6 ++++++
 3 files changed, 19 insertions(+)

--- a/Documentation/mtd/spi-nor.txt
+++ b/Documentation/mtd/spi-nor.txt
@@ -60,3 +60,6 @@ The main API is spi_nor_scan(). Before y
 initialize the necessary fields for spi_nor{}. Please see
 drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to fsl-quadspi.c
 when you want to write a new driver for a SPI NOR controller.
+Another API is spi_nor_restore(), this is used to restore the status of SPI
+flash chip such as addressing mode. Call it whenever detach the driver from
+device or reboot the system.
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -2665,6 +2665,16 @@ static int spi_nor_init(struct spi_nor *
 	return 0;
 }
 
+void spi_nor_restore(struct spi_nor *nor)
+{
+	/* restore the addressing mode */
+	if ((nor->addr_width == 4) &&
+	    (JEDEC_MFR(nor->info) != SNOR_MFR_SPANSION) &&
+	    !(nor->info->flags & SPI_NOR_4B_OPCODES))
+		set_4byte(nor, nor->info, 0);
+}
+EXPORT_SYMBOL_GPL(spi_nor_restore);
+
 int spi_nor_scan(struct spi_nor *nor, const char *name,
 		 const struct spi_nor_hwcaps *hwcaps)
 {
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -394,4 +394,10 @@ struct spi_nor_hwcaps {
 int spi_nor_scan(struct spi_nor *nor, const char *name,
 		 const struct spi_nor_hwcaps *hwcaps);
 
+/**
+ * spi_nor_restore_addr_mode() - restore the status of SPI NOR
+ * @nor:	the spi_nor structure
+ */
+void spi_nor_restore(struct spi_nor *nor);
+
 #endif