mtd: spi-nor: sfdp: detect Soft Reset sequence support from BFPT

A Soft Reset sequence will return the flash to Power-on-Reset (POR)
state. It consists of two commands: Soft Reset Enable and Soft Reset.
Find out if the sequence is supported from BFPT DWORD 16.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201005153138.6437-12-p.yadav@ti.com

drivers/mtd/spi-nor/core.h

@@ -27,6 +27,7 @@ enum spi_nor_option_flags {
 	SNOR_F_HAS_4BIT_BP      = BIT(12),
 	SNOR_F_HAS_SR_BP3_BIT6  = BIT(13),
 	SNOR_F_IO_MODE_EN_VOLATILE = BIT(14),
+	SNOR_F_SOFT_RESET	= BIT(15),
 };
 
 struct spi_nor_read_command {

drivers/mtd/spi-nor/sfdp.c

@@ -608,6 +608,10 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
 		break;
 	}
 
+	/* Soft Reset support. */
+	if (bfpt.dwords[BFPT_DWORD(16)] & BFPT_DWORD16_SWRST_EN_RST)
+		nor->flags |= SNOR_F_SOFT_RESET;
+
 	/* Stop here if not JESD216 rev C or later. */
 	if (bfpt_header->length == BFPT_DWORD_MAX_JESD216B)
 		return spi_nor_post_bfpt_fixups(nor, bfpt_header, &bfpt,

drivers/mtd/spi-nor/sfdp.h

@@ -90,6 +90,8 @@ struct sfdp_bfpt {
 #define BFPT_DWORD15_QER_SR2_BIT1_NO_RD		(0x4UL << 20)
 #define BFPT_DWORD15_QER_SR2_BIT1		(0x5UL << 20) /* Spansion */
 
+#define BFPT_DWORD16_SWRST_EN_RST		BIT(12)
+
 #define BFPT_DWORD18_CMD_EXT_MASK		GENMASK(30, 29)
 #define BFPT_DWORD18_CMD_EXT_REP		(0x0UL << 29) /* Repeat */
 #define BFPT_DWORD18_CMD_EXT_INV		(0x1UL << 29) /* Invert */