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[13/14] mtd: nand: invalidate cache on unaligned reads

Message ID 1315426421-16243-14-git-send-email-computersforpeace@gmail.com
State Accepted
Commit 6d77b9d0af57409c918ab9501866233082546ba6
Headers show

Commit Message

Brian Norris Sept. 7, 2011, 8:13 p.m. UTC
In rare cases, we are given an unaligned parameter `from' in
`nand_do_read_ops()'. In such cases, we use the page cache
(chip->buffers->databuf) as an intermediate buffer before dumping to the
client buffer. However, there are also cases where this buffer is not
cleanly reusable. In those cases, we need to make sure that we
explicitly invalidate the cache.

This patch prevents accidental reusage of the page cache, and for me,
this solves some problems I come across when reading a corrupted BBT
from flash (NAND_BBT_USE_FLASH and NAND_BBT_NO_OOB).

Note: the rare "unaligned" case is a result of the extra BBT pattern +
version located in the data area instead of OOB.

Also, this patch disables caching on raw reads, since we are reading
without error correction. This is, obviously, prone to errors and should
not be cached.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
---
 drivers/mtd/nand/nand_base.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)
diff mbox

Patch

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index c9767b5..51653d9 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1479,14 +1479,22 @@  static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
 			else
 				ret = chip->ecc.read_page(mtd, chip, bufpoi,
 							  page);
-			if (ret < 0)
+			if (ret < 0) {
+				if (!aligned)
+					/* Invalidate page cache */
+					chip->pagebuf = -1;
 				break;
+			}
 
 			/* Transfer not aligned data */
 			if (!aligned) {
 				if (!NAND_SUBPAGE_READ(chip) && !oob &&
-				    !(mtd->ecc_stats.failed - stats.failed))
+				    !(mtd->ecc_stats.failed - stats.failed) &&
+				    (ops->mode != MTD_OPS_RAW))
 					chip->pagebuf = realpage;
+				else
+					/* Invalidate page cache */
+					chip->pagebuf = -1;
 				memcpy(buf, chip->buffers->databuf + col, bytes);
 			}