sf: Add memory mapped read support

Qspi controller can have a memory mapped port which can be used for
data read. Added support to enable memory mapped port read.

This patch enables the following:
- It enables exchange of memory map address between mtd and qspi
through the introduction of "memory_map" flag.
- Add support to communicate to the driver that memory mapped
 transfer is to be started through introduction of new flags like
"SPI_XFER_MEM_MAP" and "SPI_XFER_MEM_MAP_END".

This will enable the spi controller to do memory mapped configurations
if required.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>

drivers/mtd/spi/sf_ops.c

@@ -269,7 +269,9 @@ int spi_flash_cmd_read_ops(struct spi_flash *flash, u32 offset,
 
 	/* Handle memory-mapped SPI */
 	if (flash->memory_map) {
+		spi_xfer(flash->spi, 0, NULL, NULL, SPI_XFER_MMAP);
 		memcpy(data, flash->memory_map + offset, len);
+		spi_xfer(flash->spi, 0, NULL, NULL, SPI_XFER_MMAP_END);
 		return 0;
 	}
 

drivers/mtd/spi/sf_probe.c

@@ -203,6 +203,7 @@ struct spi_flash *spi_flash_validate_params(struct spi_slave *spi, u8 *idcode)
 	flash->page_size = (ext_jedec == 0x4d00) ? 512 : 256;
 	flash->sector_size = params->sector_size;
 	flash->size = flash->sector_size * params->nr_sectors;
+	flash->memory_map = spi->memory_map;
 
 	/* Compute erase sector and command */
 	if (params->flags & SECT_4K) {

include/spi.h

@@ -27,6 +27,8 @@
 /* SPI transfer flags */
 #define SPI_XFER_BEGIN	0x01			/* Assert CS before transfer */
 #define SPI_XFER_END	0x02			/* Deassert CS after transfer */
+#define SPI_XFER_MMAP	0x08			/* Memory Mapped start */
+#define SPI_XFER_MMAP_END	0x10		/* Memory Mapped End */
 
 /* Header byte that marks the start of the message */
 #define SPI_PREAMBLE_END_BYTE		0xec
@@ -46,6 +48,7 @@ struct spi_slave {
 	unsigned int bus;
 	unsigned int cs;
 	unsigned int max_write_size;
+	void *memory_map;
 };
 
 /**