mtd: spi-nor: Add a RWW flag

Introduce a new (no SFDP) flag for the feature that we are about to
support: Read While Write. This means, if the chip has several banks and
supports RWW, once a page of data to write has been transferred into the
chip's internal SRAM, another read operation happening on a different
bank can be performed during the tPROG delay.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20230328154105.448540-7-miquel.raynal@bootlin.com
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>

drivers/mtd/spi-nor/core.c

@@ -2530,6 +2530,9 @@ static void spi_nor_init_flags(struct spi_nor *nor)
 
 	if (flags & NO_CHIP_ERASE)
 		nor->flags |= SNOR_F_NO_OP_CHIP_ERASE;
+
+	if (flags & SPI_NOR_RWW)
+		nor->flags |= SNOR_F_RWW;
 }
 
 /**

drivers/mtd/spi-nor/core.h

@@ -130,6 +130,7 @@ enum spi_nor_option_flags {
 	SNOR_F_IO_MODE_EN_VOLATILE = BIT(11),
 	SNOR_F_SOFT_RESET	= BIT(12),
 	SNOR_F_SWP_IS_VOLATILE	= BIT(13),
+	SNOR_F_RWW		= BIT(14),
 };
 
 struct spi_nor_read_command {
@@ -462,6 +463,7 @@ struct spi_nor_fixups {
  *   NO_CHIP_ERASE:           chip does not support chip erase.
  *   SPI_NOR_NO_FR:           can't do fastread.
  *   SPI_NOR_QUAD_PP:         flash supports Quad Input Page Program.
+ *   SPI_NOR_RWW:             flash supports reads while write.
  *
  * @no_sfdp_flags:  flags that indicate support that can be discovered via SFDP.
  *                  Used when SFDP tables are not defined in the flash. These
@@ -513,6 +515,7 @@ struct flash_info {
 #define NO_CHIP_ERASE			BIT(7)
 #define SPI_NOR_NO_FR			BIT(8)
 #define SPI_NOR_QUAD_PP			BIT(9)
+#define SPI_NOR_RWW			BIT(10)
 
 	u8 no_sfdp_flags;
 #define SPI_NOR_SKIP_SFDP		BIT(0)

drivers/mtd/spi-nor/debugfs.c

@@ -25,6 +25,7 @@ static const char *const snor_f_names[] = {
 	SNOR_F_NAME(IO_MODE_EN_VOLATILE),
 	SNOR_F_NAME(SOFT_RESET),
 	SNOR_F_NAME(SWP_IS_VOLATILE),
+	SNOR_F_NAME(RWW),
 };
 #undef SNOR_F_NAME