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authorunsik Kim <donari75@gmail.com>2009-07-28 08:52:07 +0200
committerJens Axboe <jens.axboe@oracle.com>2009-07-28 08:52:07 +0200
commiteb32baec15c38ae6f06cb898a9f791578c5f8c79 (patch)
treeecc439936edd9cb629a24e473a67241a4d2a586c
parent48f5690d45b79ffeedc5ab24243b576056f1d2ff (diff)
downloadblackbird-op-linux-eb32baec15c38ae6f06cb898a9f791578c5f8c79.tar.gz
blackbird-op-linux-eb32baec15c38ae6f06cb898a9f791578c5f8c79.zip
mg_disk: fix reading invalid status when use polling driver
When using polling driver, little delay is required to access status register. Without this, host might read invalid status. Signed-off-by: unsik Kim <donari75@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
-rw-r--r--drivers/block/mg_disk.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/block/mg_disk.c b/drivers/block/mg_disk.c
index 5b120eab2baa..6440d5945414 100644
--- a/drivers/block/mg_disk.c
+++ b/drivers/block/mg_disk.c
@@ -219,6 +219,16 @@ static unsigned int mg_wait(struct mg_host *host, u32 expect, u32 msec)
host->error = MG_ERR_NONE;
expire = jiffies + msecs_to_jiffies(msec);
+ /* These 2 times dummy status read prevents reading invalid
+ * status. A very little time (3 times of mflash operating clk)
+ * is required for busy bit is set. Use dummy read instead of
+ * busy wait, because mflash's PLL is machine dependent.
+ */
+ if (prv_data->use_polling) {
+ status = inb((unsigned long)host->dev_base + MG_REG_STATUS);
+ status = inb((unsigned long)host->dev_base + MG_REG_STATUS);
+ }
+
status = inb((unsigned long)host->dev_base + MG_REG_STATUS);
do {
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