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From: "Alan Chandler" <alan@chandlerfamily.org.uk>
To: Jens Axboe <axboe@suse.de>
Cc: Alan Chandler <alan@chandlerfamily.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: ide-cd problem
Date: Mon, 22 Nov 2004 12:53:41 +0000	[thread overview]
Message-ID: <E1CWDhN-00040Y-E6@home.chandlerfamily.org.uk> (raw)
In-Reply-To: <20041122113150.GF10463@suse.de>

Jens Axboe writes: 

> On Mon, Nov 22 2004, Alan Chandler wrote:
>> Jens Axboe writes: 

>> >400ns is the correctl value. Your writing is a little unclear to me -
>> >did it work or not, with that change alone? 
>> > 
>> 
>> To be clear ...  
>> 
>> 
>> I have modified ide-cd.c with  
>> 
>> 1) ndelay(400) at the head of cdrom_newpc_intr()  
>> 
>> 2) Alan Cox's patch in the place he originally identified for it to go  
>> 
>> 3) Some printk's in cdrom_newpc_intr() after the point where it reads the 
>> status and IREASON and length registers and just for the purposes of 
>> diagnostics.  
>> 
>> With only those changes it now works. 
> 
> You are not answering my question :-) 
> 
> Here's is Alans patch as I posted some mails ago. Does it work with that
> alone?? I'm curious of it is enough. It should not be necessary to incur
> extra delay in the interrupt handler, if it is invoked from a real irq.

Sorry, I misunderstood what you meant.  I presume you think that the 
interrupt may be triggered immediately the command packet has been sent but 
before 400ns delay had occurred. 

NO - with Alan's patch alone, this did not work. 

The delay seesm to be needed in the path between the interrupt occuring and 
the IDE_STATUS_REG being read. 

I had seen an note on a web site that said that there was two delays 
required in the ATA/ATAPI spec - the 400ns which Alan's patch deals with and 
a shorter delay (one PIO cycle) between busy being cleared and DRQ reaching 
the correct state where the technique had been to read the ALTSTATUS 
register.  That was why I had tried that approach but found it not to work. 

(I have subsequently downloaded a copy of the full spec and haven't been 
able to find this - but then its just short of 500 pages of dense text:-)). 

Thinking about it now, I tried the ALTSTATUS delay before applying Alan's 
patch, so maybe its the some of the two delays that maybe necessary.  If you 
think its appropriate I will try that again this evening. 

 --
Alan Chandler
alan@chandlerfamily.org.uk 


  reply	other threads:[~2004-11-22 12:55 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 [this message]
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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