Re: sata suspend resume ...

[Matt Mackall <mpm@selenic.com>]

On Fri, Apr 21, 2006 at 09:44:59PM +0100, Hugh Dickins wrote:
> On Fri, 21 Apr 2006, Pavel Machek wrote:
> > 
> > Not sure why it needs time. Waiting for disk to spin up?
> 
> I don't know, and can't hear, but doubt it (I can't see why
> it'd need disk spun up just to do an ata_dev_set_xfermode).
> 
> > Will it recover from the timeout?
> 
> No, after that wait for 30 seconds, it degenerates into attempting I/O,
> getting errors, remounting the root readonly, can't get much further.
> 
> > Would sticking ata_set_mode() at the end of timeout routine help?
> 
> Well, moving the ata_set_mode after the ata_start_drive does help:
> then the ata_start_drive times out and fails, but that does not seem
> to matter at all, and the ata_set_mode then succeeds and all is well.
> I guess that amounts to what you meant; but all the same, I won't be
> alone in preferring to wait 2 seconds than 30 seconds!
> 
> But you've made me try a bit harder, and the patch below, waiting for
> ATA_BUSY to clear, copying a line used in several other places there,
> fixes it in a much more satisfactory way than mdelay(2000).  (I checked
> how long it in fact was waiting, saw various waits between 0.8s and 1.3s).
> 
> This is a patch I'd not be ashamed to send Jeff Garzik cc linux-ide,
> even if we can't name precisely why it's ATA_BUSY then.  But I'll
> give it a day or so of real-life suspend/resuming first - Arkadiusz
> and I both noticed we're more likely to resume successfully after
> a brief suspend, so longer suspends are needed for proper testing.

Well this looks like definite progress. Does kind of look like
spinning up.

> +		ata_busy_sleep(ap, ATA_TMOUT_BOOT_QUICK, ATA_TMOUT_BOOT);

Huh. That function actually "busy sleeps". How aptly named.

-- 
Mathematics is the supreme nostalgia of our time.