[U-Boot] [PATCH] sf: Add SPI_FLASH_4BYTE_MODE_ONLY option to support 4-byte mode

[Stefan Roese]

Some SPI NOR chips only support 4-byte mode addressing. Here the default
3-byte mode does not work and leads to incorrect accesses. Setting this
option enables the use of such SPI NOR chips, that only support this
4-byte mode.

This was noticed on the LinkIt Smart 7688 modul, which is equipped with
an Macronix MX25L25635F device. But this device does *NOT* support
switching to 3-byte mode via the EX4B command.

Signed-off-by: Stefan Roese <sr at denx.de>
Cc: Jagan Teki <jagan at openedev.com>
---
 drivers/mtd/spi/Kconfig       | 9 +++++++++
 drivers/mtd/spi/sf_internal.h | 5 +++++
 drivers/mtd/spi/spi_flash.c   | 7 +++++++
 3 files changed, 21 insertions(+)

diff --git a/drivers/mtd/spi/Kconfig b/drivers/mtd/spi/Kconfig
index 4484cf8195..5738cd66e8 100644
--- a/drivers/mtd/spi/Kconfig
+++ b/drivers/mtd/spi/Kconfig
@@ -49,6 +49,15 @@ config SF_DUAL_FLASH
 	  Enable this option to support two flash memories connected to a single
 	  controller. Currently Xilinx Zynq qspi supports this.
 
+config SPI_FLASH_4BYTE_MODE_ONLY
+	bool "SPI 4-byte mode only supported"
+	depends on SPI_FLASH
+	help
+	  Some SPI NOR chips only support 4-byte mode addressing. Here
+	  the default 3-byte mode does not work and leads to incorrect
+	  accesses. Setting this option enables the use of such SPI
+	  NOR chips, that only support this 4-byte mode.
+
 if SPI_FLASH
 
 config SPI_FLASH_ATMEL
diff --git a/drivers/mtd/spi/sf_internal.h b/drivers/mtd/spi/sf_internal.h
index 4f63cacc64..78be6e442f 100644
--- a/drivers/mtd/spi/sf_internal.h
+++ b/drivers/mtd/spi/sf_internal.h
@@ -26,7 +26,12 @@ enum spi_nor_option_flags {
 };
 
 #define SPI_FLASH_3B_ADDR_LEN		3
+#define SPI_FLASH_4B_ADDR_LEN		4
+#ifdef CONFIG_SPI_FLASH_4BYTE_MODE_ONLY
+#define SPI_FLASH_CMD_LEN		(1 + SPI_FLASH_4B_ADDR_LEN)
+#else
 #define SPI_FLASH_CMD_LEN		(1 + SPI_FLASH_3B_ADDR_LEN)
+#endif
 #define SPI_FLASH_16MB_BOUN		0x1000000
 
 /* CFI Manufacture ID's */
diff --git a/drivers/mtd/spi/spi_flash.c b/drivers/mtd/spi/spi_flash.c
index c159124259..3b26d8ca88 100644
--- a/drivers/mtd/spi/spi_flash.c
+++ b/drivers/mtd/spi/spi_flash.c
@@ -23,9 +23,16 @@
 static void spi_flash_addr(u32 addr, u8 *cmd)
 {
 	/* cmd[0] is actual command */
+#ifdef CONFIG_SPI_FLASH_4BYTE_MODE_ONLY
+	cmd[1] = addr >> 24;
+	cmd[2] = addr >> 16;
+	cmd[3] = addr >> 8;
+	cmd[4] = addr >> 0;
+#else
 	cmd[1] = addr >> 16;
 	cmd[2] = addr >> 8;
 	cmd[3] = addr >> 0;
+#endif
 }
 
 static int read_sr(struct spi_flash *flash, u8 *rs)
-- 
2.18.0