On another machine, I saw this with write caching turned off:
ata2.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x6 frozen
ata2.00: cmd 61/08:00:28:1f:80/00:00:00:00:00/40 tag 0 ncq 4096 out
res 40/00:00:40:1f:80/00:00:00:00:00/40 Emask 0x4 (timeout)
ata2.00: status: { DRDY }
ata2: hard resetting link
ata2: softreset failed (device not ready)
ata2: hard resetting link
ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata2.00: configured for UDMA/133
ata2: EH complete
ata2.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x6 frozen
ata2.00: cmd 61/08:00:28:1f:80/00:00:00:00:00/40 tag 0 ncq 4096 out
res 40/00:00:20:1f:80/00:00:00:00:00/40 Emask 0x4 (timeout)
ata2.00: status: { DRDY }
ata2: hard resetting link
ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata2.00: qc timeout (cmd 0xef)
ata2.00: failed to set xfermode (err_mask=0x4)
ata2: hard resetting link
ata2: softreset failed (device not ready)
ata2: hard resetting link
ata2: softreset failed (device not ready)
ata2: hard resetting link
ata2: link is slow to respond, please be patient (ready=0)
ata2: softreset failed (device not ready)
ata2: limiting SATA link speed to 1.5 Gbps
ata2: hard resetting link
ata2: softreset failed (device not ready)
ata2: reset failed, giving up
ata2.00: disabled