Comment 16 for bug 1318218

Further to my earlier comment, it seems that these settings don't entirely eliminate SATA errors. I've tried with both "medium_power" and "min_power" as settings for the link_power_management_policy, and still get some errors. They're slightly different, and also less regular; around 10 every 5 minutes as opposed to once a second on "max_performance". Here's a sample of the errors produced on "medium_power". I've added some line breaks to make the difference in timestamps easier to follow.

[367622.113130] ata1.00: exception Emask 0x10 SAct 0x0 SErr 0x4040000 action 0xe frozen
[367622.113134] ata1.00: irq_stat 0x80000040, connection status changed
[367622.113136] ata1: SError: { CommWake DevExch }
[367622.113139] ata1.00: failed command: WRITE DMA EXT
[367622.113143] ata1.00: cmd 35/00:08:80:7b:0d/00:00:16:00:00/e0 tag 24 dma 4096 out
[367622.113143] res 50/00:00:77:3f:ff/00:00:0f:00:00/ef Emask 0x10 (ATA bus error)
[367622.113145] ata1.00: status: { DRDY }
[367622.113148] ata1: hard resetting link
[367622.836250] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
[367622.836665] ata1.00: unexpected _GTF length (8)
[367622.837097] ata1.00: unexpected _GTF length (8)
[367622.837103] ata1.00: configured for UDMA/33
[367622.837188] ata1: EH complete

[367668.468555] ata1.00: exception Emask 0x10 SAct 0x0 SErr 0x4040000 action 0xe frozen
[367668.468565] ata1.00: irq_stat 0x80000040, connection status changed
[367668.468570] ata1: SError: { CommWake DevExch }
[367668.468578] ata1.00: failed command: READ DMA
[367668.468588] ata1.00: cmd c8/00:08:f8:e6:e0/00:00:00:00:00/ee tag 26 dma 4096 in
[367668.468588] res 50/00:00:a7:e1:4a/00:00:1b:00:00/e0 Emask 0x10 (ATA bus error)
[367668.468594] ata1.00: status: { DRDY }
[367668.468601] ata1: hard resetting link
[367669.192455] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
[367669.192953] ata1.00: unexpected _GTF length (8)
[367669.193458] ata1.00: unexpected _GTF length (8)
[367669.193462] ata1.00: configured for UDMA/33
[367669.193568] ata1: EH complete

[367676.039388] ata1.00: exception Emask 0x10 SAct 0x0 SErr 0x4040000 action 0xe frozen
[367676.039393] ata1.00: irq_stat 0x80000040, connection status changed
[367676.039396] ata1: SError: { CommWake DevExch }
[367676.039401] ata1.00: failed command: WRITE DMA EXT
[367676.039407] ata1.00: cmd 35/00:08:20:f2:fd/00:00:15:00:00/e0 tag 28 dma 4096 out
[367676.039407] res 50/00:00:07:e3:7d/00:00:12:00:00/e0 Emask 0x10 (ATA bus error)
[367676.039410] ata1.00: status: { DRDY }
[367676.039414] ata1: hard resetting link
[367676.762336] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
[367676.762813] ata1.00: unexpected _GTF length (8)
[367676.763339] ata1.00: unexpected _GTF length (8)
[367676.763342] ata1.00: configured for UDMA/33
[367676.763497] ata1: EH complete

[368192.378495] ata1.00: exception Emask 0x10 SAct 0x0 SErr 0x4040000 action 0xe frozen
[368192.378505] ata1.00: irq_stat 0x80000040, connection status changed
[368192.378510] ata1: SError: { CommWake DevExch }
[368192.378517] ata1.00: failed command: WRITE DMA
[368192.378528] ata1.00: cmd ca/00:80:10:d9:6a/00:00:00:00:00/ee tag 15 dma 65536 out
[368192.378528] res 50/00:00:00:00:00/00:00:00:00:00/a0 Emask 0x10 (ATA bus error)
[368192.378533] ata1.00: status: { DRDY }
[368192.378541] ata1: hard resetting link
[368193.101144] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
[368193.101540] ata1.00: unexpected _GTF length (8)
[368193.101964] ata1.00: unexpected _GTF length (8)
[368193.101967] ata1.00: configured for UDMA/33
[368193.102043] ata1: EH complete

[368383.548958] ata1.00: exception Emask 0x10 SAct 0x0 SErr 0x4040000 action 0xe frozen
[368383.548963] ata1.00: irq_stat 0x80000040, connection status changed
[368383.548966] ata1: SError: { CommWake DevExch }
[368383.548969] ata1.00: failed command: WRITE DMA EXT
[368383.548973] ata1.00: cmd 35/00:98:e0:60:0f/00:00:16:00:00/e0 tag 30 dma 77824 out
[368383.548973] res 50/00:00:00:00:00/00:00:00:00:00/a0 Emask 0x10 (ATA bus error)
[368383.548975] ata1.00: status: { DRDY }
[368383.548979] ata1: hard resetting link
[368384.270310] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
[368384.270711] ata1.00: unexpected _GTF length (8)
[368384.271160] ata1.00: unexpected _GTF length (8)
[368384.271166] ata1.00: configured for UDMA/33
[368384.271246] ata1: EH complete