ATAng: DMA timeout, ICRC errors, ...

I've discovered several problems on my system with the ATAng driver.
Most of these seem related to one particular disk drive, but the
disk used to work fine with the older driver, so I assume the fault
lies with the new driver.

1) under heavy I/O, frequent occurences of "ad0: TIMEOUT - WRITE_DMA retrying".
Sometimes READ_DMA instead.
The IDE configuration:
	ata0 -> 80-pin cable, one ATA100 capable 180Gb hard disk drive
	ata1 -> 40-pin cable, a DVD reader and a DVD burner.

See dmesg.1, attached. This is the configuration where I get "TIMEOUT
- WRITE_DMA" on ad0.

2) I tried to add another (older) IDE drive which I put in the
following (non optimal) configuration:
	ata0 -> 80-pin cable, 180Gb hard disk, DVD burner
	ata1 -> 40-pin cable, 80Gb hard disk, DVD reader

The driver correctly disables the ATA66 mode on ata0, given that
the DVD burner is not ATA66-compliant. But no such message on ata1,
and I get many ICRC errors when accessing ad1, making ad1 totally
unusable.

See dmesg.2 attached.

3) both disk drives on ata0, both DVD drives on ata1:
ad0 (identified as ATA-6) is usable but thrashes on heavy I/O (DMA
problems when reading a DV file with fwcontrol(8)). Same problem
as 1) above, except the messages I get about timeouts are related
to firewire -- but I'm quite certain the problem is not firewire-related
as reading from firewire works perfectly fine when the file is
stored on the other drive.

Under heavy disk access (without firewire involved) I also get
bunches of:
ad0: WARNING - READ_DMA UDMA ICRC error (retrying request)
ad0: WARNING - READ_DMA UDMA ICRC error (retrying request)
ad0: WARNING - READ_DMA UDMA ICRC error (retrying request)
ad0: WARNING - READ_DMA UDMA ICRC error (retrying request)

Reading from/writing to ad1 (identified as ATA-5) exhibits no
problem.

See dmesg.3 attached.
-- 
Pierre Beyssac	      	    pb_at_fasterix.frmug.org pb_at_fasterix.freenix.org
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