Odd behaviour of device in response to idleimmediate with unload

[Elias Oltmanns <eo@nebensachen.de>]

Hi all,

apparently, we have the first case of a quirky implementation of
idleimmediate with unload feature in a device, or I'm barking up the
wrong tree, of course. Evgeni Golov has reported the following on
hdaps-devel:

Evgeni Golov <sargentd@die-welt.net> wrote:
> Hi,
>
> I have a ThinkPad Z61m with a 100GB S-ATA TOSHIBA MK1032GSX.
[...]
> Now I thought I should try the new interface and compiled 2.6.28-rc2,
[...]
> After that I could park the heads and got the following in dmesg:
>
> ata1: exception Emask 0x10 SAct 0x0 SErr 0x50000 action 0xf
> ata1: SError: { PHYRdyChg CommWake }
> ata1: hard resetting link
> ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
> ata1.00: ACPI cmd ef/02:00:00:00:00:a0 succeeded
> ata1.00: ACPI cmd f5/00:00:00:00:00:a0 filtered out
> ata1.00: ACPI cmd ef/10:03:00:00:00:a0 filtered out
> ata1.00: ACPI cmd ef/02:00:00:00:00:a0 succeeded
> ata1.00: ACPI cmd f5/00:00:00:00:00:a0 filtered out
> ata1.00: ACPI cmd ef/10:03:00:00:00:a0 filtered out
> ata1.00: configured for UDMA/100
> ata1.00: configured for UDMA/100
> ata1: EH complete
> sd 0:0:0:0: [sda] 195371568 512-byte hardware sectors: (100 GB/93.1 GiB)
> sd 0:0:0:0: [sda] Write Protect is off
> sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
> sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't
> support DPO or FUA
> sd 0:0:0:0: [sda] 195371568 512-byte hardware sectors: (100 GB/93.1 GiB)
> sd 0:0:0:0: [sda] Write Protect is off
> sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
> sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't
> support DPO or FUA

The only explanation I could come up with so far is that the head park
command, for some reason or other, causes the device to set
SERR_PHYRDY_CHG and SERR_COMM_WAKE in serror, thus triggering the
handling of hotplug events. Do you have any idea what's really going on
here and what can / should be done about it?

Regards,

Elias