r3874 - trunk/src/target/kernel/patches

[werner at sita.openmoko.org]

Author: werner
Date: 2008-01-17 19:08:02 +0100 (Thu, 17 Jan 2008)
New Revision: 3874

Added:
   trunk/src/target/kernel/patches/fix-hwecc-2410.patch
Modified:
   trunk/src/target/kernel/patches/series
Log:
NAND ECC error correction mis-calculated the bit position, thus turning a
correctable single-bit error into two errors. Fittingly, also reported
uncorrectable errors as success.

Note that, unlike 2.6.24, 2.6.22.5 requires ecc.correct to return -1 to signal
an uncorrectable error, not just any negative value. So this patch is not
identical to the one in the 2.6.24 tree.

series:
- added fix-hwecc-2410.patch

fix-hwecc-2410.patch:  
- drivers/mtd/nand/s3c2410.c (s3c2410_nand_correct_data): use Pn bits to
  calculate error position, not Pn'
- drivers/mtd/nand/s3c2410.c (s3c2410_nand_correct_data): don't report
  uncorrectable errors as "no error"



Added: trunk/src/target/kernel/patches/fix-hwecc-2410.patch
===================================================================
--- trunk/src/target/kernel/patches/fix-hwecc-2410.patch	2008-01-17 18:07:09 UTC (rev 3873)
+++ trunk/src/target/kernel/patches/fix-hwecc-2410.patch	2008-01-17 18:08:02 UTC (rev 3874)
@@ -0,0 +1,59 @@
+S3C24xx ECC mis-calculates the bit to flip:
+http://lists.infradead.org/pipermail/linux-mtd/2007-October/019586.html
+If the error couldn't be corrected, we returned "no problem" :-(
+http://lists.infradead.org/pipermail/linux-mtd/2007-October/019615.html
+
+Note that, unlike 2.6.24, 2.6.22.5 requires ecc.correct to return -1 to signal
+an uncorrectable error, not just any negative value.
+
+Signed-off-by: Werner Almesberger <werner at openmoko.org>
+
+Index: linux-2.6.24-rc7/drivers/mtd/nand/s3c2410.c
+===================================================================
+--- linux-2.6.24-rc7.orig/drivers/mtd/nand/s3c2410.c
++++ linux-2.6.24-rc7/drivers/mtd/nand/s3c2410.c
+@@ -364,23 +364,21 @@
+ 	    ((diff2 ^ (diff2 >> 1)) & 0x55) == 0x55) {
+ 		/* calculate the bit position of the error */
+ 
+-		bit  = (diff2 >> 2) & 1;
+-		bit |= (diff2 >> 3) & 2;
+-		bit |= (diff2 >> 4) & 4;
++		bit  = ((diff2 >> 3) & 1) |
++		       ((diff2 >> 4) & 2) |
++		       ((diff2 >> 5) & 4);
+ 
+ 		/* calculate the byte position of the error */
+ 
+-		byte  = (diff1 << 1) & 0x80;
+-		byte |= (diff1 << 2) & 0x40;
+-		byte |= (diff1 << 3) & 0x20;
+-		byte |= (diff1 << 4) & 0x10;
+-
+-		byte |= (diff0 >> 3) & 0x08;
+-		byte |= (diff0 >> 2) & 0x04;
+-		byte |= (diff0 >> 1) & 0x02;
+-		byte |= (diff0 >> 0) & 0x01;
+-
+-		byte |= (diff2 << 8) & 0x100;
++		byte = ((diff2 << 7) & 0x100) |
++		       ((diff1 << 0) & 0x80)  |
++		       ((diff1 << 1) & 0x40)  |
++		       ((diff1 << 2) & 0x20)  |
++		       ((diff1 << 3) & 0x10)  |
++		       ((diff0 >> 4) & 0x08)  |
++		       ((diff0 >> 3) & 0x04)  |
++		       ((diff0 >> 2) & 0x02)  |
++		       ((diff0 >> 1) & 0x01);
+ 
+ 		dev_dbg(info->device, "correcting error bit %d, byte %d\n",
+ 			bit, byte);
+@@ -399,7 +397,7 @@
+ 	if ((diff0 & ~(1<<fls(diff0))) == 0)
+ 		return 1;
+ 
+-	return 0;
++	return -1;
+ }
+ 
+ /* ECC functions

Modified: trunk/src/target/kernel/patches/series
===================================================================
--- trunk/src/target/kernel/patches/series	2008-01-17 18:07:09 UTC (rev 3873)
+++ trunk/src/target/kernel/patches/series	2008-01-17 18:08:02 UTC (rev 3874)
@@ -58,3 +58,5 @@
 # work in progress. hangs the kernel, if enabled.
 gta02-acc.patch
 gta02-leds.patch
+# bad bug
+fix-hwecc-2410.patch