Re: PIO with SSDs: needs a long DRQ-after-command timeout for WRITEs

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Wednesday 31 December 2008, Mark Lord wrote:
> Alan Cox wrote:
> >> So.. how long does libata and current IDE allow for initial DRQ assertion?
> >> It should probably be at least 500msec or more now.
> > 
> > I think we need to rewrite the PIO code paths to use disable/enable_irq
> > masking first before getting into adding long delays on PIO paths.
> ..
> 
> Yeah, that would be a good thing to do.

Unless shared IRQs come into the picture -- in such case disabling IRQ
for 0.5sec doesn't sound too sexy...

> But in the meanwhile, a longer timeout there doesn't affect
> any currently working systems -- they'll still wait only as long
> as they currently do.  And a longer timeout *will* enable these
> SSDs to work where they otherwise would not.
> 
> But perhaps the timeout is already long enough?
> I don't know where the current timeout is hiding in libata.  :)

When it comes to IDE the timeout is defined by WAIT_DRQ in <linux/ide.h>
and is currently set to 100ms.  There should be no problem with increasing
it if it would help to get some devices to work (please just send a patch).

Thanks,
Bart