[PATCH 3/7 revised] mmc_spi: adjust for delayed data token response

[Wolfgang Mües]

From: Wolfgang Muees <wolfgang.mues@xxxxxxxxxxxx>

o 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@xxxxxxxxxxxx>

---

This is the revised patch #3, to apply after the already accepted 
patches #1,2 and #5. It contains the bugfix and a better explanation
of what is going on here.

diff -uprN 2_6_29_rc7_patch125/drivers/mmc/host/mmc_spi.c 2_6_29_rc7_patch1253/drivers/mmc/host/mmc_spi.c
--- 2_6_29_rc7_patch125/drivers/mmc/host/mmc_spi.c	2009-03-11 13:00:06.000000000 +0100
+++ 2_6_29_rc7_patch1253/drivers/mmc/host/mmc_spi.c	2009-03-16 12:15:36.000000000 +0100
@@ -612,6 +612,7 @@ mmc_spi_writeblock(struct mmc_spi_host *
 	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 *
 	 * 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.
-	 */
-	switch (SPI_MMC_RESPONSE_CODE(scratch->status[0])) {
+	 *
+	 * 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!!!
+	 */
+	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 *
 	/* 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);

---
regards

i. A. Wolfgang Mües
-- 
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Hardware Development
Telefon: +49 (0)5306 9219 0
Telefax: +49 (0)5306 9219 94 
E-Mail: Wolfgang.Mues@xxxxxxxxxxxx
Web: http://www.auerswald.de
 
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