Re: ide-cd problem

[Alan Chandler]

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@xxxxxxxxxxxxxxxxxxxxx 

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/