[RFC/PATCH 3/3] drivers: mtd: devices: Add memory mapped read support.

[Sourav Poddar]

Add memory mapped flash read support. In memory mapped, only the len, from
and t->rx_buf is required from the flash side, while other configuration
will be taken care of from the respective controller side with the help
of the transfer flag(memory_map).

Signed-off-by: Sourav Poddar <sourav.poddar at ti.com>
---

 drivers/mtd/devices/m25p80.c |   13 +++++++++++--
 include/linux/spi/spi.h      |    2 ++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index dc9bcbf..9d09bad 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -102,6 +102,7 @@ struct m25p {
 	u8			*command;
 	bool			fast_read;
 	bool			quad_read;
+	bool			mmap_read;
 };
 
 static inline struct m25p *mtd_to_m25p(struct mtd_info *mtd)
@@ -440,10 +441,15 @@ static int m25p80_quad_read(struct mtd_info *mtd, loff_t from, size_t len,
 	spi_message_init(&m);
 	memset(t, 0, (sizeof(t)));
 
+	if (flash->mmap_read)
+		t[0].memory_map = 1;
 	t[0].tx_buf = flash->command;
-	t[0].len = m25p_cmdsz(flash) + (flash->quad_read ? 1 : 0);
+	t[0].len = flash->mmap_read ? from : m25p_cmdsz(flash) +
+				(flash->quad_read ? 1 : 0);
 	spi_message_add_tail(&t[0], &m);
 
+	if (flash->mmap_read)
+		t[1].memory_map = 1;
 	t[1].rx_buf = buf;
 	t[1].len = len;
 	t[1].rx_nbits = SPI_NBITS_QUAD;
@@ -470,7 +476,7 @@ static int m25p80_quad_read(struct mtd_info *mtd, loff_t from, size_t len,
 
 	spi_sync(flash->spi, &m);
 
-	*retlen = m.actual_length - m25p_cmdsz(flash) -
+	*retlen = flash->mmap_read ? len : m.actual_length - m25p_cmdsz(flash) -
 			(flash->quad_read ? 1 : 0);
 
 	mutex_unlock(&flash->lock);
@@ -1207,6 +1213,9 @@ static int m25p_probe(struct spi_device *spi)
 	if (spi->mode && SPI_RX_QUAD)
 		flash->quad_read = true;
 
+	if (spi->mode && SPI_RX_MMAP)
+		flash->mmap_read = true;
+
 	flash->command = kmalloc(MAX_CMD_SIZE + (flash->fast_read ? 1 :
 				(flash->quad_read ? 1 : 0)), GFP_KERNEL);
 	if (!flash->command) {
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 4d634d6..a6ffb52 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -91,6 +91,7 @@ struct spi_device {
 #define	SPI_TX_QUAD	0x200			/* transmit with 4 wires */
 #define	SPI_RX_DUAL	0x400			/* receive with 2 wires */
 #define	SPI_RX_QUAD	0x800			/* receive with 4 wires */
+#define SPI_RX_MMAP	0x1000			/* Memory mapped read */
 	u8			bits_per_word;
 	int			irq;
 	void			*controller_state;
@@ -557,6 +558,7 @@ struct spi_transfer {
 	u16		delay_usecs;
 	u32		speed_hz;
 
+	bool	memory_map;
 	struct list_head transfer_list;
 };
 
-- 
1.7.1