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@milecki.pl>
Acked-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

diff --git a/drivers/mtd/devices/bcm47xxsflash.c b/drivers/mtd/devices/bcm47xxsflash.c
index 4decd8c..e2bd818 100644 (file)
--- 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 (file)
--- 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