Re: Regression on linux-next (next-20250708)

Borah, Chaitanya Kumar
2025-07-29T08:43:35Z

On 7/29/2025 4:03 AM, Damien Le Moal wrote:
> On 7/29/25 01:24, Borah, Chaitanya Kumar wrote:
>>
>>
>> On 7/28/2025 9:41 AM, Damien Le Moal wrote:
>>> On 7/25/25 3:43 PM, Borah, Chaitanya Kumar wrote:
>>>> For some context in our kms_pm_rpm tests, we enable min_power policy for SATA
>>>> so that we can reach deep runtime power states and restore the original policy
>>>> after finishing. [5][6]
>>>>
>>>> IIUC, the above change is based on spec and not something which can be
>>>> reverted. So as I see it, we have to drop this code path for external ports.
>>>> However I am not sure if we can achieve deep power states without enforcing it
>>>> through the sysfs entry.
>>>>
>>>> Atleast for the basic-rte subtest, the test passes if we comment out the
>>>> functions controlling the SATA ports. We will need more testing to determine if
>>>> this approach work. Any thoughts on it?
>>>>
>>>> Also, are there other ways to detect a port is external other than receiving
>>>> EOPNOTSUPP on the sysfs write?
>>>
>>> The attached patch adds the "link_power_management_supported" sysfs device
>>> attribute for drives connected to AHCI. Would that work for you ?
>>>
>>
>> Yes this could work. I quickly hacked the test to ignore writing policy
>> if this file returns 0.
>>
>> Here is the state of the machine I am testing on.
>>
>> /sys/class/scsi_host/host0/link_power_management_supported: 0
>> /sys/class/scsi_host/host1/link_power_management_supported: 0
>> /sys/class/scsi_host/host2/link_power_management_supported: 0
>> /sys/class/scsi_host/host3/link_power_management_supported: 0
>> /sys/class/scsi_host/host4/link_power_management_supported: 1
>> /sys/class/scsi_host/host5/link_power_management_supported: 1
>> /sys/class/scsi_host/host6/link_power_management_supported: 1
>> /sys/class/scsi_host/host7/link_power_management_supported: 1
>
> Looks good. My test machine looks exactly like this too.
> I will send out this patch as it is useful anyway regardless of external/hotplug
> ports since not all adapters/drives support LPM.
>
> When posting this, can I tag it as a solution to the regression ?
>

Yes sure you can use it.

Adding Imre to the conversation if he has anything to say about this
change in our test.

Regards

Chaitanya

> And in addition to this patch, I will work on a flexible way of ignoring hotplug.
>
>