From eb32baec15c38ae6f06cb898a9f791578c5f8c79 Mon Sep 17 00:00:00 2001
From: unsik Kim <donari75@gmail.com>
Date: Tue, 28 Jul 2009 08:52:07 +0200
Subject: [PATCH] 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>
---
drivers/block/mg_disk.c | 10 ++++++++++
1 file changed, 10 insertions(+)
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 {