sata_sil boot failure with 2.6.35

["Jan Beulich" <JBeulich@novell.com>]

Hi,

on one of my systems (the only one with that sort of controller) boot
fails with .35 due to an identify failure for the drive that has the root
partition (and others):

libata version 3.00 loaded.
sata_sil 0000:00:12.0: version 2.4
sata_sil 0000:00:12.0: enabling device (0005 -> 0007)
  alloc irq_desc for 22 on node -1
  alloc kstat_irqs on node -1
sata_sil 0000:00:12.0: PCI INT A -> GSI 22 (level, low) -> IRQ 22
scsi0 : sata_sil
scsi1 : sata_sil
ata1: SATA max UDMA/100 mmio m512@0xc0000000 tf 0xc0000080 irq 22
ata2: SATA max UDMA/100 mmio m512@0xc0000000 tf 0xc00000c0 irq 22
input: ImExPS/2 Generic Explorer Mouse as /devices/platform/i8042/serio1/input/input1
ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
ata1.00: NODEV after polling detection
ata2: SATA link down (SStatus 0 SControl 300)

With some debugging printk-s added I found that "status" as passed
from ata_sff_pio_task() to ata_sff_hsm_move() is 0x50 (instead of
the expected 0x58), and I also found that adding a certain delay
at the top of ata_sff_pio_task() for just the very first invocation
makes the problem go away: putting udelay(400) there works,
while udelay(300) isn't sufficient.

2.6.34.x is working fine.

The controller is reported as

00:12.0 IDE interface [0101]: ATI Technologies Inc IXP SB400 Serial ATA Controller [1002:4379]

Thanks for any hints towards debugging or resolving this problem.

Jan