On 09/13/2012 04:39 PM, Jack Wang wrote:
>>>>> For hard disk runtime power off, Is there (hardware?) requirement for
>>> hard
>>>>> drive to support similar feature?
>>>>
>>>> No requirement for hard drive, as it does not need to remote wake up
>>>> itself while powered off.
>>>>
>>>> Please note that there is a v7 sent yesterday, you may want to take a
>>>> look at that instead of v6.
>>>>
>>>> And the runtime power off of hard drive is dropped from that patch set,
>>>> I'll submit it in another patch set(pretty small changes needed).
>>>>
>>>> Thanks,
>>>> Aaron
>>> [Jack Wang] Thanks Aaron for quick replay, for disk runtime power off,
> will
>>> it a different proach from block runtime power management patch set
> from
>>> Lin Ming?
>>
>> I suppose you mean the "block layer runtime pm" from Lin Ming?
>> No, they are different things.
>>
>> That patch set introduced a mechanism to decide when a device can enter
>> runtime suspend based on block layer request, while my patch cares about
>> when it is runtime suspended, how to remove its power.
>>
>> Thanks,
>> Aaron
> [Jack Wang] Thanks, but I still not get how to remove hard disk power?
> Through acpi? But libata acpi not cover scsi disk right? Sorry if my
> question is too stupid.
When scsi disk is runtime suspended, the ata port it attached to will be
runtime suspended, and then the power will be removed through ACPI.
Please check libata-acpi.c, function ata_acpi_set_state.
The parent/child relationship of the devices:
ata_host
ata_port
scsi_host
scsi_target
scsi_device
If you have more questions on how it works, please send email only
to me, other people might be too busy to read such emails :-)
Thanks,
Aaron
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