Re: AHCI - remove probing of ata2

[Greg Trounson <gregt@maths.otago.ac.nz>]

At the risk of sounding like a "me too" post:

I also have an Asus P5W-DH, with the following drives connected:

SATA: ST3250820AS, connected to sata1
PATA: HL-DT-ST GSA-H12N, ATAPI DVD Writer, Primary master

On bootup of 2.6.19 and 2.6.20, the kernel stalls for 1 minute when probing sata2, 
eventually giving up and continuing the boot process.  There is no physical sata2 
connector on the Motherboard, just solder lugs between sata1 and sata3.  From other users 
I understand this is really a Silicon Image SIL4723 SATA to 2-Port SATA splitter.  It is 
detected by the kernel as a disk, as below.

The relevant part of the boot process looks like:
...
libata version 2.00 loaded.
ahci 0000:00:1f.2: version 2.0
ACPI: PCI Interrupt 0000:00:1f.2[B] -> GSI 23 (level, low) -> IRQ 22
PCI: Setting latency timer of device 0000:00:1f.2 to 64
ahci 0000:00:1f.2: AHCI 0001.0100 32 slots 4 ports 3 Gbps 0xf impl SATA mode
ahci 0000:00:1f.2: flags: 64bit ncq led clo pio slum part
ata1: SATA max UDMA/133 cmd 0xF882A900 ctl 0x0 bmdma 0x0 irq 219
ata2: SATA max UDMA/133 cmd 0xF882A980 ctl 0x0 bmdma 0x0 irq 219
ata3: SATA max UDMA/133 cmd 0xF882AA00 ctl 0x0 bmdma 0x0 irq 219
ata4: SATA max UDMA/133 cmd 0xF882AA80 ctl 0x0 bmdma 0x0 irq 219
scsi0 : ahci
ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
ata1.00: ATA-7, max UDMA/133, 488397168 sectors: LBA48 NCQ (depth 31/32)
ata1.00: ata1: dev 0 multi count 16
ata1.00: configured for UDMA/133
scsi1 : ahci
ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)

...waits 20 seconds...

ata2.00: qc timeout (cmd 0xec)
ata2.00: failed to IDENTIFY (I/O error, err_mask=0x104)

...waits 5 seconds...

ata2: port is slow to respond, please be patient (Status 0x80)

...waits 30 seconds...

ata2: port failed to respond (30 secs, Status 0x80)
ata2: COMRESET failed (device not ready)
ata2: hardreset failed, retrying in 5 secs

...waits 5 seconds...

ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata2.00: ATA-6, max UDMA/133, 640 sectors: LBA
ata2.00: ata2: dev 0 multi count 1
ata2.00: configured for UDMA/133
scsi2 : ahci
ata3: SATA link down (SStatus 0 SControl 300)
...

A bit of poking about shows:

fdisk -l /dev/sdb
Disk /dev/sdb: 0 MB, 327680 bytes
255 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/sdb doesn't contain a valid partition table

So it presents itself as a 320k disk, filled with zeroes as below:

dd if=/dev/sdb |hexdump
0000000 0000 0000 0000 0000 0000 0000 0000 0000
*
0050000

640+0 records in
640+0 records out
327680 bytes (328 kB) copied, 0.0106662 seconds, 30.7 MB/s

Note that this is not a fatal error.  The machine still boots eventually, but the 
seemingly mandatory 60 second pause makes startup rather cumbersome for the user.

So far none of the suggested fixes have managed to stop ata2 from being detected. 
(noprobe=ata2, irqpoll, etc).  I understand this problem wasn't present in 2.6.16 so the 
problem must lie in some patch since then.  I see Tejun is working towards patches for 
this and I would be happy to try them here.

thanks,
Greg