mmc_spi: adjust for delayed data token response

Some cards are not able to send the data token in time, but
miss the time frame for some bits(!). So synchronize to the
start of the token.
Signed-off-by: Wolfgang Muees <wolfgang.mues@auerswald.de>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/host/mmc_spi.c

@@ -612,6 +612,7 @@ mmc_spi_writeblock(struct mmc_spi_host *host, struct spi_transfer *t,
 	struct spi_device	*spi = host->spi;
 	int			status, i;
 	struct scratch		*scratch = host->data;
+	u32			pattern;
 
 	if (host->mmc->use_spi_crc)
 		scratch->crc_val = cpu_to_be16(
@@ -639,8 +640,27 @@ mmc_spi_writeblock(struct mmc_spi_host *host, struct spi_transfer *t,
 	 * doesn't necessarily tell whether the write operation succeeded;
 	 * it just says if the transmission was ok and whether *earlier*
 	 * writes succeeded; see the standard.
+	 *
+	 * In practice, there are (even modern SDHC-)cards which are late
+	 * in sending the response, and miss the time frame by a few bits,
+	 * so we have to cope with this situation and check the response
+	 * bit-by-bit. Arggh!!!
 	 */
-	switch (SPI_MMC_RESPONSE_CODE(scratch->status[0])) {
+	pattern  = scratch->status[0] << 24;
+	pattern |= scratch->status[1] << 16;
+	pattern |= scratch->status[2] << 8;
+	pattern |= scratch->status[3];
+
+	/* First 3 bit of pattern are undefined */
+	pattern |= 0xE0000000;
+
+	/* left-adjust to leading 0 bit */
+	while (pattern & 0x80000000)
+		pattern <<= 1;
+	/* right-adjust for pattern matching. Code is in bit 4..0 now. */
+	pattern >>= 27;
+
+	switch (pattern) {
 	case SPI_RESPONSE_ACCEPTED:
 		status = 0;
 		break;
@@ -671,8 +691,9 @@ mmc_spi_writeblock(struct mmc_spi_host *host, struct spi_transfer *t,
 	/* Return when not busy.  If we didn't collect that status yet,
 	 * we'll need some more I/O.
 	 */
-	for (i = 1; i < sizeof(scratch->status); i++) {
-		if (scratch->status[i] != 0)
+	for (i = 4; i < sizeof(scratch->status); i++) {
+		/* card is non-busy if the most recent bit is 1 */
+		if (scratch->status[i] & 0x01)
 			return 0;
 	}
 	return mmc_spi_wait_unbusy(host, timeout);