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Message-ID: <435E6C74.8010406@ru.mvista.com>
Date: Tue, 25 Oct 2005 21:33:40 +0400
From: Sergei Shtylylov <sshtylyov@ru.mvista.com>
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Cc: Konstantin Baidarov <kbaidarov@ru.mvista.com>
Subject: [PATCH] CFI: prevent the false software timeouts on writes
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Hello.

       We've noticed that sometimes "MTD do_write_buffer(): software timeout"
message was printed out when writing to a Fujitsu NOR flash.
       It turned out that this was because of a race in the timeout handling
do_write_buffer(). A small timeout of (HZ / 1000) + 1 is used there, and
sometimes if the timer interrupt handling takes more than one or even two
jiffies (which is 1-2 ms with HZ == 1000) and that interrupt happens just
after chip_ready() call, the driver bails out from a ready polling loop
despite the chip has actually become ready while all those interrupts were
handled. To deal with this issue, extra check for chip ready is neccessary on
timeout expiration (and the checks should better be reordered).
       As do_write_oneword() uses the same approach, it needs to also be changed.

Signed-off-by: Konstantin Baidarov <kbaidarov@ru.mvista.com>
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>





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 filename="cfi_cmdset_0002-write-timeout.patch"

Index: drivers/mtd/chips/cfi_cmdset_0002.c
===================================================================
RCS file: /home/cvs/mtd/drivers/mtd/chips/cfi_cmdset_0002.c,v
retrieving revision 1.120
diff -a -u -p -r1.120 cfi_cmdset_0002.c
--- drivers/mtd/chips/cfi_cmdset_0002.c	20 Jul 2005 21:01:13 -0000	1.120
+++ drivers/mtd/chips/cfi_cmdset_0002.c	25 Oct 2005 15:38:44 -0000
@@ -1014,16 +1014,16 @@ static int __xipram do_write_oneword(str
 			continue;
 		}
 
-		if (chip_ready(map, adr))
-			break;
-
-		if (time_after(jiffies, timeo)) {
+		if (time_after(jiffies, timeo) && !chip_ready(map, adr)){
 			xip_enable(map, chip, adr);
 			printk(KERN_WARNING "MTD %s(): software timeout\n", __func__);
 			xip_disable(map, chip, adr);
-                        break;
+			break;
 		}
 
+		if (chip_ready(map, adr))
+			break;
+
 		/* Latency issues. Drop the lock, wait a while and retry */
 		UDELAY(map, chip, adr, 1);
 	}
@@ -1275,13 +1275,13 @@ static int __xipram do_write_buffer(stru
 			continue;
 		}
 
+		if (time_after(jiffies, timeo) && !chip_ready(map, adr))
+			break;
+
 		if (chip_ready(map, adr)) {
 			xip_enable(map, chip, adr);
 			goto op_done;
 		}
-		    
-		if( time_after(jiffies, timeo))
-			break;
 
 		/* Latency issues. Drop the lock, wait a while and retry */
 		UDELAY(map, chip, adr, 1);





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