Re: libata fails to recover from HSM violation involving DRQ status

[Mark Lord <liml@rtr.ca>]

> 
>>> Ah.. one more thing, is this draining also needed after DMA commands or
>>> only after PIO commands?
> 
> My drive doesn't do IDENTIFY_DMA, so I fed it a READ_DMA instead
> with "no data", and libata recovered without draining. 

More specifically, here's what happens for READ_DMA(1 sector)
with "NON_DATA" specified (same circustances as the failed IDENTIFY):

ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x2 frozen
ata1.00: cmd c8/00:01:00:00:00/00:00:00:00:00/40 tag 0 cdb 0x0 data 0
         res 40/00:00:00:00:00/00:00:00:00:00/40 Emask 0x4 (timeout)
ata1: port is slow to respond, please be patient (Status 0xd0)
ata1: port failed to respond (30 secs, Status 0xd0)
ata1: soft resetting port
ATA: abnormal status 0xD0 on port 0x000101f7
ATA: abnormal status 0xD0 on port 0x000101f7
ata1.00: configured for UDMA/100
ata1: EH complete
SCSI device sda: 312581808 512-byte hdwr sectors (160042 MB)
sda: Write Protect is off
sda: Mode Sense: 00 3a 00 00
SCSI device sda: write cache: enabled, read cache: enabled, doesn't support DPO or FUA

So no draining, and all is well again.
Odds look pretty good that this is just a PIO thing.

-ml