[PATCH V2] mtd: bcm47xxsflash: support reading flash out of mapping window

[Rafał Miłecki]

From: Rafał Miłecki <rafal at milecki.pl>

For reading flash content we use MMIO but it's possible to read only
first 16 MiB this way. It's simply an arch design/limitation.
To support flash sizes bigger than 16 MiB implement indirect access
using ChipCommon registers.
This has been tested using MX25L25635F.

Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
V2: Simplify line writing to buf
    Add some trivial comment for OPCODE_ST_READ4B
    Both requested by Marek
---
 drivers/mtd/devices/bcm47xxsflash.c | 12 +++++++++++-
 drivers/mtd/devices/bcm47xxsflash.h |  3 +++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/devices/bcm47xxsflash.c b/drivers/mtd/devices/bcm47xxsflash.c
index 4decd8c..8d4c1db 100644
--- a/drivers/mtd/devices/bcm47xxsflash.c
+++ b/drivers/mtd/devices/bcm47xxsflash.c
@@ -110,7 +110,17 @@ static int bcm47xxsflash_read(struct mtd_info *mtd, loff_t from, size_t len,
 	if ((from + len) > mtd->size)
 		return -EINVAL;
 
-	memcpy_fromio(buf, b47s->window + from, len);
+	if (from + len <= BCM47XXSFLASH_WINDOW_SIZE) {
+		memcpy_fromio(buf, b47s->window + from, len);
+	} else {
+		size_t i;
+
+		for (i = 0; i < len; i++) {
+			b47s->cc_write(b47s, BCMA_CC_FLASHADDR, from++);
+			bcm47xxsflash_cmd(b47s, OPCODE_ST_READ4B);
+			*buf++ = b47s->cc_read(b47s, BCMA_CC_FLASHDATA);
+		}
+	}
 	*retlen = len;
 
 	return len;
diff --git a/drivers/mtd/devices/bcm47xxsflash.h b/drivers/mtd/devices/bcm47xxsflash.h
index 1564b62..6b478af 100644
--- a/drivers/mtd/devices/bcm47xxsflash.h
+++ b/drivers/mtd/devices/bcm47xxsflash.h
@@ -3,6 +3,8 @@
 
 #include <linux/mtd/mtd.h>
 
+#define BCM47XXSFLASH_WINDOW_SIZE		SZ_16M
+
 /* Used for ST flashes only. */
 #define OPCODE_ST_WREN		0x0006		/* Write Enable */
 #define OPCODE_ST_WRDIS		0x0004		/* Write Disable */
@@ -16,6 +18,7 @@
 #define OPCODE_ST_RES		0x03ab		/* Read Electronic Signature */
 #define OPCODE_ST_CSA		0x1000		/* Keep chip select asserted */
 #define OPCODE_ST_SSE		0x0220		/* Sub-sector Erase */
+#define OPCODE_ST_READ4B	0x6313		/* Read Data Bytes in 4Byte address */
 
 /* Used for Atmel flashes only. */
 #define OPCODE_AT_READ				0x07e8
-- 
2.10.1