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DateFri, 21 Apr 2006 15:50:42 -0500
FromMatt Mackall <>
SubjectRe: sata suspend resume ...
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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.
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