Re: [PATCH] CFI: prevent the false software timeouts on writes

Vitaly Wool
2005-10-31T14:25:18Z

Hi Sergey,

I'm going to verify if this works with XIP and get back to you.

Best regards,
Vitaly

Sergei Shtylylov wrote:

> 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>
>
>
>
>
>------------------------------------------------------------------------
>
>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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