Comment 25 for bug 344093

My particular problem seems to be caused by the VIA VT8251 controller causing errors on the SATA bus and the SATA bus dropping back to UDMA/33. See editied version of Kernel log below:

2010-04-25 16:42:12 [ 1705.688583] ata3.00: exception Emask 0x10 SAct 0x0 SErr 0x580100 action 0x6 frozen
2010-04-25 16:42:12 [ 1705.688589] ata3.00: irq_stat 0x08000000, interface fatal error
2010-04-25 16:42:12 [ 1705.688594] ata3: SError: { UnrecovData 10B8B Dispar Handshk }
2010-04-25 16:42:12 [ 1705.688604] ata3.00: cmd 35/00:00:1f:59:fa/00:04:16:00:00/e0 tag 0 dma 524288 out
2010-04-25 16:42:12 [ 1705.688605] res 50/00:00:1e:59:fa/00:00:16:00:00/e0 Emask 0x10 (ATA bus error)
2010-04-25 16:42:12 [ 1705.688609] ata3.00: status: { DRDY }
2010-04-25 16:42:12 [ 1705.688615] ata3: hard resetting link
2010-04-25 16:42:13 [ 1706.212549] ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
2010-04-25 16:42:13 [ 1706.332620] ata3.00: configured for UDMA/133

2010-04-25 16:46:34 [ 1968.012445] ata3.00: limiting speed to UDMA/100:PIO4
2010-04-25 16:46:34 [ 1968.012457] ata3.00: exception Emask 0x0 SAct 0x0 SErr 0x180000 action 0x6 frozen
2010-04-25 16:46:34 [ 1968.012467] ata3: SError: { 10B8B Dispar }
2010-04-25 16:46:34 [ 1968.012484] ata3.00: cmd 35/00:00:9f:e2:81/00:04:17:00:00/e0 tag 0 dma 524288 out
2010-04-25 16:46:34 [ 1968.012486] res 40/00:00:6e:08:7b/00:00:17:00:00/e0 Emask 0x4 (timeout)
2010-04-25 16:46:34 [ 1968.012493] ata3.00: status: { DRDY }
2010-04-25 16:46:34 [ 1968.012520] ata3: hard resetting link
2010-04-25 16:46:35 [ 1968.540878] ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
2010-04-25 16:46:35 [ 1968.644397] ata3.00: configured for UDMA/100
2010-04-25 16:46:35 [ 1968.644424] ata3: EH complete

2010-04-25 16:49:14 [ 2128.010067] ata3.00: limiting speed to UDMA/33:PIO4
2010-04-25 16:49:14 [ 2128.010078] ata3.00: exception Emask 0x0 SAct 0x0 SErr 0x180000 action 0x6 frozen
2010-04-25 16:49:14 [ 2128.010088] ata3: SError: { 10B8B Dispar }
2010-04-25 16:49:14 [ 2128.010104] ata3.00: cmd 35/00:00:47:a5:8a/00:04:17:00:00/e0 tag 0 dma 524288 out
2010-04-25 16:49:14 [ 2128.010107] res 40/00:00:3e:9d:8a/00:00:17:00:00/e0 Emask 0x4 (timeout)
2010-04-25 16:49:14 [ 2128.010114] ata3.00: status: { DRDY }
2010-04-25 16:49:14 [ 2128.010123] ata3: hard resetting link
2010-04-25 16:49:15 [ 2128.542591] ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
2010-04-25 16:49:15 [ 2128.634875] ata3.00: configured for UDMA/33
2010-04-25 16:49:15 [ 2128.634907] ata3: EH complete

This appears to be similar to the above problem although with a different SATA controller.

See my blog http://tinyurl.com/2v5cnpu for more info.

I think this bug and Bug #282536 are similar if not the same, and possibly Bug #190492.