Re: [patch]: ide dma timeout retry in pio

[Andre Hedrick]

On Tue, 29 May 2001, Jens Axboe wrote:

> This is bull shit. If IDE didn't muck around with the request so much in
> the first place, the info could always be trusted. Even so, we have the
> hard_* numbers to go by. So this argument does not hold.

Maybe if you looked at the new code model as a whole you would see that
the request-forking is gone.  The object is to preserve a copy of the io
instructions out to the registers to not have to repeat the do_request
call unless it is a do or die thing.  Also it is good to carry a copy of
the local request even if it is never used.  Also are you resetting the
pointer (back to the geginning) on rq->buffer on the retry?

You first flush the DMA engine and issue a device soft reset not using the
current drive reset, is presevers the hwgroup->busy state and allows the
request to be retried without reinserting.

> > As I recall, there is a way to reinsert the faulted request, but that
> 
> Again, look at the patch. The request is never off the list, so there is
> never a reason to reinsert. hwgroup->busy is cleared (and, again for
> good measure, hwgroup->rq), so ide_do_request/start_request will get the
> same request that we just handled.

I will have to poke in a few flags to verify this but if you say so.

> > means the request_struct needs fault counter.  If it is truly a DMA error
> 
> ->errors, it's already there.

Wrong location to poke and by that time it requires a full retry.
The new code would have had the task structs filled with the error.

> > because of re-seeks then the timeout value for that request must be
> > expanded.
> 
> Yep

In some cases yes, but it would be better if I had a standard counter that
meant something.  Also changing the jiffie counter in ide_delay_50ms to a
mdelay may have done more harm than good.

Andre Hedrick
Linux ATA Development
ASL Kernel Development
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