mtd: bcm47xxsflash: support reading flash out of mapping window

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=ccc38234fdc70120be79e7fb2df5c27ca5cd4c8a
Commit:     ccc38234fdc70120be79e7fb2df5c27ca5cd4c8a
Parent:     9c8d7ff32a0aa001ac8506180e1662ecdf927f32
Author:     Rafał Miłecki <rafal at milecki.pl>
AuthorDate: Wed Feb 8 23:53:44 2017 +0100
Committer:  Brian Norris <computersforpeace at gmail.com>
CommitDate: Wed Feb 8 15:07:59 2017 -0800

    mtd: bcm47xxsflash: support reading flash out of mapping window
    
    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>
    Acked-by: Marek Vasut <marek.vasut at gmail.com>
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
---
 drivers/mtd/devices/bcm47xxsflash.c | 24 +++++++++++++++++++++---
 drivers/mtd/devices/bcm47xxsflash.h |  3 +++
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/devices/bcm47xxsflash.c b/drivers/mtd/devices/bcm47xxsflash.c
index 4decd8c..e2bd818 100644
--- a/drivers/mtd/devices/bcm47xxsflash.c
+++ b/drivers/mtd/devices/bcm47xxsflash.c
@@ -105,15 +105,33 @@ static int bcm47xxsflash_read(struct mtd_info *mtd, loff_t from, size_t len,
 			      size_t *retlen, u_char *buf)
 {
 	struct bcm47xxsflash *b47s = mtd->priv;
+	size_t orig_len = len;
 
 	/* Check address range */
 	if ((from + len) > mtd->size)
 		return -EINVAL;
 
-	memcpy_fromio(buf, b47s->window + from, len);
-	*retlen = len;
+	/* Read as much as possible using fast MMIO window */
+	if (from < BCM47XXSFLASH_WINDOW_SZ) {
+		size_t memcpy_len;
 
-	return len;
+		memcpy_len = min(len, (size_t)(BCM47XXSFLASH_WINDOW_SZ - from));
+		memcpy_fromio(buf, b47s->window + from, memcpy_len);
+		from += memcpy_len;
+		len -= memcpy_len;
+		buf += memcpy_len;
+	}
+
+	/* Use indirect access for content out of the window */
+	for (; len; len--) {
+		b47s->cc_write(b47s, BCMA_CC_FLASHADDR, from++);
+		bcm47xxsflash_cmd(b47s, OPCODE_ST_READ4B);
+		*buf++ = b47s->cc_read(b47s, BCMA_CC_FLASHDATA);
+	}
+
+	*retlen = orig_len;
+
+	return orig_len;
 }
 
 static int bcm47xxsflash_write_st(struct mtd_info *mtd, u32 offset, size_t len,
diff --git a/drivers/mtd/devices/bcm47xxsflash.h b/drivers/mtd/devices/bcm47xxsflash.h
index 1564b62..b2d7b38 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_SZ			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 addressing mode */
 
 /* Used for Atmel flashes only. */
 #define OPCODE_AT_READ				0x07e8