freifunkist-firmware/target/linux/ramips/patches-4.14/0054-mtd-spi-nor-w25q256-respect-default-mode.patch

--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -142,20 +142,29 @@ static int read_fsr(struct spi_nor *nor)
  * location. Return the configuration register value.
  * Returns negative if error occurred.
  */
-static int read_cr(struct spi_nor *nor)
+static int _read_cr(struct spi_nor *nor, u8 reg)
 {
 	int ret;
 	u8 val;
 
-	ret = nor->read_reg(nor, SPINOR_OP_RDCR, &val, 1);
+	ret = nor->read_reg(nor, reg, &val, 1);
 	if (ret < 0) {
-		dev_err(nor->dev, "error %d reading CR\n", ret);
+		dev_err(nor->dev, "error %d reading %s\n", ret,
+			(reg==SPINOR_OP_RDCR)?"CR":"XCR");
 		return ret;
 	}
 
 	return val;
 }
 
+static inline int read_cr(struct spi_nor *nor) {
+	return _read_cr(nor, SPINOR_OP_RDCR);
+}
+
+static inline int read_xcr(struct spi_nor *nor) {
+	return _read_cr(nor, SPINOR_OP_RDXCR);
+}
+
 /*
  * Write status register 1 byte
  * Returns negative if error occurred.
@@ -2895,9 +2904,16 @@ int spi_nor_scan(struct spi_nor *nor, co
 	} else if (mtd->size > 0x1000000) {
 		/* enable 4-byte addressing if the device exceeds 16MiB */
 		nor->addr_width = 4;
-		if (info->flags & SPI_NOR_4B_READ_OP)
-			spi_nor_set_4byte_read(nor, info);
-		else if (JEDEC_MFR(info) == SNOR_MFR_SPANSION ||
+		if (info->flags & SPI_NOR_4B_READ_OP) {
+			if (JEDEC_MFR(info) == SNOR_MFR_WINBOND) {
+				ret = read_xcr(nor);
+				if (!(ret > 0 && (ret & XCR_DEF_4B_ADDR_MODE)))
+					spi_nor_set_4byte_read(nor, info);
+				else
+					set_4byte(nor, info, 1);
+			} else
+				spi_nor_set_4byte_read(nor, info);
+		} else if (JEDEC_MFR(info) == SNOR_MFR_SPANSION ||
 			 info->flags & SPI_NOR_4B_OPCODES)
 			spi_nor_set_4byte_opcodes(nor, info);
 		else
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -103,6 +103,7 @@
 #define SPINOR_OP_EN4B		0xb7	/* Enter 4-byte mode */
 #define SPINOR_OP_EX4B		0xe9	/* Exit 4-byte mode */
 #define SPINOR_OP_WREAR		0xc5	/* Write extended address register */
+#define SPINOR_OP_RDXCR		0x15	/* Read extended configuration register */
 
 /* Used for Spansion flashes only. */
 #define SPINOR_OP_BRWR		0x17	/* Bank register write */
@@ -135,6 +136,7 @@
 
 /* Configuration Register bits. */
 #define CR_QUAD_EN_SPAN		BIT(1)	/* Spansion Quad I/O */
+#define XCR_DEF_4B_ADDR_MODE	BIT(1)	/* Winbond 4B mode default */
 
 /* Status Register 2 bits. */
 #define SR2_QUAD_EN_BIT7	BIT(7)