From: Alan Chandler <alan@chandlerfamily.org.uk>
To: Jens Axboe <axboe@suse.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: ide-cd problem
Date: Fri, 26 Nov 2004 23:39:01 +0000 [thread overview]
Message-ID: <200411262339.01306.alan@chandlerfamily.org.uk> (raw)
In-Reply-To: <200411232149.31701.alan@chandlerfamily.org.uk>
On Tuesday 23 November 2004 21:49, Alan Chandler wrote:
>
> Before, I thought my hardware was a little out of spec - now I think there
> is something else at play here.
>
Firstly, I think there might be another race condition like the one Alan Cox
found. I attach a patch below with the fix for that (against 2.6.10-rc2, an
including Alan's patch) I'm not 100% sure its necessary, but it seems fix a
variation I have been seeing.
With it in place, and apart from the ongoing issue - see below, I have managed
to remove the delay in drive_is_ready() altogether without any ill effects.
[my reading of the ATA spec is that 400ns is needed after reading the status
reg before IRQ is removed, I had wondered whether it would be better to
record the time here and then check whether we had used up the 400ns just
before returning from the interrupt state]
> Nov 23 20:37:33 kanger kernel: ide-cd:cdrom_newpc_intr - cmd=0x0 stat=0x50
> ireason=3 len=2048 rq len=0
..
> Nov 23 20:37:33 kanger kernel: ide-cd:cdrom_newpc_intr - cmd=0x1b stat=0x58
> ireason=2 len=0 rq len=0
I think these two lines hold the crux of the problem. They are the result of
a printk in cdrom_newpc_intr just after reading the interrupt reason register
and byte count registers.
However, I have been unable to get any closer as to why DRQ gets set.
The patch
--- ide-cd.c 2004-11-26 20:29:59.000000000 +0000
+++ ide-cd.patch.c 2004-11-26 20:51:23.000000000 +0000
@@ -890,8 +890,12 @@
ide_execute_command(drive, WIN_PACKETCMD, handler, ATAPI_WAIT_PC,
cdrom_timer_expiry);
return ide_started;
} else {
+ unsigned long flags;
+ spin_lock_irqsave(&ide_lock, flags);
+ HWIF(drive)->OUTBSYNC(drive, WIN_PACKETCMD, IDE_COMMAND_REG);
+ ndelay(400);
+ spin_unlock_irqrestore(&ide_lock, flags);
/* packet command */
- HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
return (*handler) (drive);
}
}
@@ -938,8 +942,12 @@
cmd_len = ATAPI_MIN_CDB_BYTES;
/* Send the command to the device. */
+ unsigned long flags;
+ spin_lock_irqsave(&ide_lock, flags);
HWIF(drive)->atapi_output_bytes(drive, rq->cmd, cmd_len);
-
+ ndelay(400);
+ spin_unlock_irqrestore(&ide_lock, flags);
+
/* Start the DMA if need be */
if (info->dma)
hwif->dma_start(drive);
--
Alan Chandler
alan@chandlerfamily.org.uk
First they ignore you, then they laugh at you,
then they fight you, then you win. --Gandhi
next prev parent reply other threads:[~2004-11-26 23:46 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-11-20 18:42 ide-cd problem Alan Chandler
2004-11-20 19:47 ` Jens Axboe
2004-11-21 0:53 ` Alan Chandler
2004-11-21 8:56 ` Jens Axboe
2004-11-21 10:25 ` Alan Chandler
2004-11-21 16:13 ` Alan Chandler
2004-11-22 7:52 ` Alan Chandler
2004-11-22 8:01 ` Jens Axboe
2004-11-22 10:30 ` Alan Chandler
2004-11-22 10:51 ` Jens Axboe
2004-11-22 11:29 ` Alan Chandler
2004-11-22 11:31 ` Jens Axboe
2004-11-22 12:53 ` Alan Chandler
2004-11-22 13:02 ` Jens Axboe
2004-11-22 19:19 ` Alan Chandler
2004-11-22 23:48 ` Alan Chandler
2004-11-23 7:13 ` Alan Chandler
2004-11-23 14:51 ` Jens Axboe
2004-11-23 21:49 ` Alan Chandler
2004-11-26 23:39 ` Alan Chandler [this message]
2004-11-29 17:29 ` Bill Davidsen
2004-11-30 8:59 ` Alan Chandler
2004-12-10 21:32 ` ide-cd problem revisited - more brainpower needed Alan Chandler
2004-12-10 23:14 ` Alan Cox
2004-12-12 0:17 ` Alan Chandler
2004-12-12 11:39 ` Alan Cox
2004-12-12 13:34 ` Alan Chandler
2004-12-14 0:20 ` Alan Chandler
2004-12-16 15:56 ` Bill Davidsen
2004-12-17 23:59 ` Alan Chandler
2004-11-24 23:19 ` ide-cd problem Alan Cox
2004-11-25 15:29 ` Jens Axboe
2004-11-25 16:25 ` Alan Cox
2004-11-25 18:12 ` Jens Axboe
2004-11-25 18:45 ` Alan Chandler
2004-11-23 18:34 ` Jeff Garzik
2004-11-23 19:13 ` Jens Axboe
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