Re: [git patches] libata updates for 3.3

[Linus Torvalds]

On Sun, Jan 8, 2012 at 4:32 PM, Jeff Garzik <jeff@xxxxxxxxxx> wrote:
>
> Summary (very little excitement at all this time):
>
> 0) Will play around with git signed tags with the next update.
>
> 1) PM improvements, including runtime suspend/resume work

Hmm. I don't know if this comes from the PM improvements or even this
particular pull, but links that aren't connected are *really* slow.

Annoyingly so.

My Macbook Air that I finally can resume reliably again used to come
back almost immediately from resume. No longer. And the reason seems
to be this:

 [  243.306149] ata_piix 0000:00:1f.2: setting latency timer to 64
 [  243.306180] bcma: Found rev 6 PMU (capabilities 0x108C2606)
 [  246.579648] ata1.01: failed to resume link (SControl 0)
 [  246.735472] ata1.00: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
 [  246.735485] ata1.01: SATA link down (SStatus 0 SControl 0)
 [  246.743632] ata1.00: ACPI cmd ef/03:46:00:00:00:a0 (SET FEATURES)
filtered out
 [  246.744353] ata1.00: configured for UDMA/100
 [  246.744537] sd 0:0:0:0: [sda] Starting disk
 [  247.769806] ata2.00: failed to resume link (SControl 0)
 [  248.796207] ata2.01: failed to resume link (SControl 0)
 [  248.807665] ata2.00: SATA link down (SStatus 4 SControl 0)
 [  248.807681] ata2.01: SATA link down (SStatus 0 SControl 0)
 [  248.808338] PM: resume of devices complete after 5511.027 msecs
 [  248.882074] PM: Finishing wakeup.

Notice the basically five-second timeout all basically for "failed to
resume link: for things that didn't have anything connected to them
anyway.

This is a bog-standard Intel controller, there's nothing odd there.

I'm pretty sure this used to be much faster, but I haven't bisected
any of it (and with all the problems I had with resume both due to
wireless and MCE, I really wouldn't want to even try).

Taking 5.5 seconds to come back from suspend-to-ram really is too
long. Not *all* of it is the SATA part, but a lot of it is.

For ATA suspend/resume, could we perhaps only resume the ports that
*used* to have something on them? And then, if somebody has plugged
something into the others, not consider that a resume thing at all,
but a hotplug thing that happens *after* the resume?

If it takes five seconds to notice new hardware after a resume, nobody
cares. But the disk we had before obviously needs to get resumed.. But
it does seem like it's the "no link" part that takes long.

Hmm? Or any other ideas?

         Linus
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