[U-Boot] [PATCH] spi: mxc: Fix data loss for non aligned write buffers.

[Martin Fuzzey]

When writing buffers that are not 32 bit aligned data loss occurs.

This can also occur when the total transfer size is not a multiple of 4 bytes
since the extra bytes are written first causing the rest to be unaligned.

This can be seen by writing to SPI flash a 57 byte file containing 00 01 .. 38:

U-Boot > dhcp data.bin
...
Bytes transferred = 57 (39 hex)
U-Boot > md.b $loadaddr
72000000: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f    ................
72000010: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f    ................
72000020: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f     !"#$%&'()*+,-./
72000030: 30 31 32 33 34 35 36 37 38 ff ff ff ff ff ff ff    012345678.......
U-Boot > sf write $loadaddr 0 $filesize

U-Boot > mw.b $loadaddr ff 100
U-Boot > sf read $loadaddr 0 100
U-Boot > md.b $loadaddr
72000000: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f    ................
72000010: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f    ................
72000020: 20 21 22 23 24 29 2a 2b 2c 31 32 33 34 ff ff ff     !"#$)*+,1234...
72000030: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................

[bytes 25-28, 2d-30, 35-38 are missing]

Activating debug in the write command gave:
spi_xchg_single: bitlen 256 dout 0x72000000 din 0x0
Sending SPI 0x10203
Sending SPI 0x4050607
Sending SPI 0x8090a0b
Sending SPI 0xc0d0e0f
Sending SPI 0x10111213
Sending SPI 0x14151617
Sending SPI 0x18191a1b
Sending SPI 0x1c1d1e1f
SPI Rx: 0xffffffff 0xffffffff
...
SPI Rx: 0xffffffff 0xffffffff
spi_xchg_single: bitlen 200 dout 0x72000020 din 0x0
Sending SPI 0x20
Sending SPI 0x21222324
Sending SPI 0x292a2b2c	<===  What happened to 25262728?
Sending SPI 0x31323334
Sending SPI 0xffffffff
...
SF: program success 57 bytes @ 0x0


The problem was that the pointer was being incremented twice for the non aligned case.

Signed-off-by: Martin Fuzzey <mfuzzey at parkeon.com>
---
 drivers/spi/mxc_spi.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/mxc_spi.c b/drivers/spi/mxc_spi.c
index 859c43f..964a2b7 100644
--- a/drivers/spi/mxc_spi.c
+++ b/drivers/spi/mxc_spi.c
@@ -274,8 +274,8 @@ int spi_xchg_single(struct spi_slave *slave, unsigned int bitlen,
 			} else {
 				data = *(u32 *)dout;
 				data = cpu_to_be32(data);
+				dout += 4;
 			}
-			dout += 4;
 		}
 		debug("Sending SPI 0x%x\n", data);
 		reg_write(&regs->txdata, data);