Hello,

I have an issue with AHCI driver, starting with kernel 3.17.0, where 
ata8 port is resetting multiple times during boot, and it takes about a 
minute until it gives up, dmesg excerpt:

[    0.698367] ata8: SATA max UDMA/133 abar m8192@0xfebfe000 port 
0xfebfe180 irq 16
[    6.052229] ata8: link is slow to respond, please be patient (ready=-19)
[   10.744229] ata8: COMRESET failed (errno=-16)
[   16.098114] ata8: link is slow to respond, please be patient (ready=-19)
[   20.790040] ata8: COMRESET failed (errno=-16)
[   26.144229] ata8: link is slow to respond, please be patient (ready=-19)
[   55.826199] ata8: COMRESET failed (errno=-16)
[   55.826386] ata8: limiting SATA link speed to 1.5 Gbps
[   60.874228] ata8: COMRESET failed (errno=-16)
[   60.874413] ata8: reset failed, giving up

In kernel 3.16.0 the same port was reported as dummy and the boot 
sequence was fast:

[    0.757323] ata8: DUMMY

I took some time, bisected between 3.16 and 3.17, and eventually found 
this commit as culprit:

commit 725c7b570fda4207e465ff8856c2c12c2645a685
Author: Antoine Ténart <antoine.tenart@free-electrons.com>
Date:   Wed Jul 30 20:13:56 2014 +0200

     ata: libahci_platform: move port_map parameters into the AHCI structure

Indeed, after reverting that commit in current 3.18-rc2, once again ata8 
is reported as dummy, and the machine boots fast.

I'm attaching the full dmesg output.

Regards,

-- 
Zlatko