linux-kernel - Re: [PATCH ide] : Increase WAIT

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Message-Id: <20091202.215738.12118816.davem@davemloft.net>
Date:	Wed, 02 Dec 2009 21:57:38 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	liml@....ca
Cc:	hancockrwd@...il.com, phdm@...qel.be, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH ide] : Increase WAIT_DRQ to support slow CF cards

From: Mark Lord <liml@....ca>
Date: Sat, 31 Oct 2009 09:56:26 -0400

> Robert Hancock wrote:
> ..
>> This has come up before:
>> http://marc.info/?l=linux-ide&m=123064513313466&w=2
>> I think this timeout should not even exist. libata has no such timeout
>> (only the overall command completion timeout), and I can't find any
>> reference in current ATA specs to the device being required to raise
>> DRQ in any particular amount of time.
> ..
> 
> The reason for the original (20ms, then 50ms) timeout was this text
> from the ATA1 specification, long since outdated:
> 
>   -  Upon receipt of a Class 3 command, the drive sets BSY within 400 nsec,
>      sets  up the sector buffer for a write operation, sets DRQ within 20
>      msec, and clears BSY within 400 nsec of setting DRQ.

Ok, I'd like to resolve this as follows.  We had stated "at least
500msec for SSD drives" so I doubled it.

This should be a pretty safe change.  The only major side effect is
that if the device really does hang before setting DRQ it will take
a full second before we notice it.

Any major objections?

ide: Increase WAIT_DRQ to accomodate some CF cards and SSD drives.

Based upon a patch by Philippe De Muyter, and feedback from Mark
Lord and Robert Hancock.

As noted by Mark Lord, the outdated ATA1 spec specifies a 20msec
timeout for setting DRQ but lots of common devices overshoot this.

Signed-off-by: David S. Miller <davem@...emloft.net>

diff --git a/include/linux/ide.h b/include/linux/ide.h
index e4135d6..0ec6129 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -125,8 +125,8 @@ struct ide_io_ports {
  * Timeouts for various operations:
  */
 enum {
-	/* spec allows up to 20ms */
-	WAIT_DRQ	= HZ / 10,	/* 100ms */
+	/* spec allows up to 20ms, but CF cards and SSD drives need more */
+	WAIT_DRQ	= 1 * HZ,	/* 1s */
 	/* some laptops are very slow */
 	WAIT_READY	= 5 * HZ,	/* 5s */
 	/* should be less than 3ms (?), if all ATAPI CD is closed at boot */
--
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