linux-kernel - [PATCH] mmc_spi: use EILSEQ for possible transmission errors

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Date:	Thu, 14 May 2009 12:24:27 +0100
From:	Wolfgang Mües <wolfgang.mues@...rswald.de>
To:	Pierre Ossman <drzeus@...eus.cx>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Matt Fleming" <matt@...sole-pimps.org>,
	"David Brownell" <dbrownell@...rs.sourceforge.net>,
	"Mike Frysinger" <vapier.adi@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] mmc_spi: use EILSEQ for possible transmission errors

From: Wolfgang Muees <wolfgang.mues@...rswald.de>

o This patch changes the reported error code for the responses
  to a command from EINVAL/EIO to EILSEQ, as EINVAL is reserved
  for non-recoverable host errors, and the responses from
  the SD/MMC card may be because of recoverable transmission
  errors in the command or in the response. Response codes
  are NOT protected by a checksum, so don't trust them.

Signed-off-by: Wolfgang Muees <wolfgang.mues@...rswald.de>

---
diff -uprN 2_6_29_rc7_patch_wearout_speedup/drivers/mmc/host/mmc_spi.c 2_6_29_rc7_patch_EILSEQ/drivers/mmc/host/mmc_spi.c
--- 2_6_29_rc7_patch_wearout_speedup/drivers/mmc/host/mmc_spi.c	2009-04-08 11:11:20.000000000 +0200
+++ 2_6_29_rc7_patch_EILSEQ/drivers/mmc/host/mmc_spi.c	2009-05-14 12:49:42.000000000 +0200
@@ -334,17 +334,18 @@ checkstatus:
 	cmd->error = 0;

 	/* Status byte: the entire seven-bit R1 response.  */
-	if (cmd->resp[0] != 0) {
-		if ((R1_SPI_PARAMETER | R1_SPI_ADDRESS
-				      | R1_SPI_ILLEGAL_COMMAND)
-				& cmd->resp[0])
-			value = -EINVAL;
-		else if (R1_SPI_COM_CRC & cmd->resp[0])
-			value = -EILSEQ;
-		else if ((R1_SPI_ERASE_SEQ | R1_SPI_ERASE_RESET)
-				& cmd->resp[0])
-			value = -EIO;
-		/* else R1_SPI_IDLE, "it's resetting" */
+	/*
+	 * Note that we have a problem here: as the response is NOT protected
+	 * by a CRC or checksum, a transmission error in the response will
+	 * be interpreted as an error code. So we map all error codes to
+	 * EILSEQ here, to allow for the upper layer to retry the command.
+	 * If one of these error codes is a non-recoverable error, retries
+	 * will do no harm.
+	 */
+
+	/* Allow only 0 and R1_SPI_IDLE here */
+	if (cmd->resp[0] & ~R1_SPI_IDLE) {
+		value = -EILSEQ;
 	}

 	switch (mmc_spi_resp_type(cmd)) {
---
regards

i. A. Wolfgang Mües
-- 
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