From: Jens Axboe <axboe@suse.de>
To: Alan Chandler <alan@chandlerfamily.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: ide-cd problem
Date: Mon, 22 Nov 2004 11:51:58 +0100 [thread overview]
Message-ID: <20041122105157.GB10463@suse.de> (raw)
In-Reply-To: <E1CWBSN-0003mF-4s@home.chandlerfamily.org.uk>
On Mon, Nov 22 2004, Alan Chandler wrote:
> Jens Axboe writes:
>
> >On Mon, Nov 22 2004, Alan Chandler wrote:
> >>On Sunday 21 November 2004 16:13, Alan Chandler wrote:
> >>...
> >>>
> >>> This seems to be some combination of frequently occuring timing problem,
> >>> and the difference treatment in cdrom_newpc_intr to cdrom_pc_intr
> >>
> >>I put a ndelay(400) at the head of cdrom_newpc_intr and the problem of
> >>DRQ being set when there was no data to transfer disappeared. It
> >>appears that my hardware is too slow.
> >>
> >>I have been reading the ATA/ATAPI - 6 spec, and it implies that the
> >>state of DRQ line need one pio cycle before being correct and that you
> >>should read the alternative status register to achieve this. I tried
> >>a simple
> >>
> >>HWIF(drive)->INB( IDE_ALTSTATUS_REG);
> >>
> >>But that made no difference.
> >
> >ALTSTATUS read should be fine as well, but the implicit delay is
> >probably better.
> >
>
> I don't know why, but the ALTSTATUS read did NOT work when I tried it
> yesterday (am currently at work using web mail to access my mail - can't do
> more until this evening). Its possible I put it in the wrong place (ie
> after the cdrom_decode_status call, but I don't think so.
>
> The ndelay(400) did work.
>
> >Is this enough to fix it? For ->drq_interrupt we already should have
> >an adequate delay, Alan fixed this one recently.
> >
>
> Yes, I had included this patch quite early in my process of tracking
> the problem down (when I corrected it like you have (add the drive
> parameter to the OUTBSYNC macro like you have, you also need to
> declare an unsigned long flags at the head of the routine that was
> also not in that patch). Indeed it was this that was the inspiration
> for the 400 nanosecs in my change. I have no idea what the right
> number should be
400ns is the correctl value. Your writing is a little unclear to me -
did it work or not, with that change alone?
--
Jens Axboe
next prev parent reply other threads:[~2004-11-22 10:56 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 [this message]
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
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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