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Message-ID: <0aecdabb-0472-34d6-447f-6a292e802683@opensource.wdc.com>
Date:   Wed, 21 Sep 2022 17:31:33 +0900
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Subject: Re: [PATCH RFC 0/6] libata/scsi/libsas: Allocate SCSI device earlier
 for ata port probe
Content-Language: en-US
To:     John Garry <john.garry@huawei.com>, jejb@linux.ibm.com,
        martin.petersen@oracle.com, hare@suse.de, hch@lst.de
Cc:     linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-scsi@vger.kernel.org, brking@us.ibm.com
References: <1663669630-21333-1-git-send-email-john.garry@huawei.com>
 <40b9e090-5ba3-1191-4fe9-80467284ae72@opensource.wdc.com>
 <0ae5000d-8e9a-da0f-b470-9f87f1b5e290@huawei.com>
From:   Damien Le Moal <damien.lemoal@opensource.wdc.com>
Organization: Western Digital Research
In-Reply-To: <0ae5000d-8e9a-da0f-b470-9f87f1b5e290@huawei.com>
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On 9/21/22 17:24, John Garry wrote:
> On 21/09/2022 05:04, Damien Le Moal wrote:
>> On 9/20/22 19:27, John Garry wrote:
>>> Currently for libata the SCSI device (sdev) associated with an=20
>>> ata_device
>>> is allocated when the port probe has completed.
>>>
>>> It's useful to have the SCSI device and its associated request queue
>>> available earlier for the port probe. Specifically if we have the
>>> request queue available, then we can:
>>> - Easily put ATA qc in SCSI cmnd priv data
>>> - Send ATA internal commands on SCSI device request queue for [0]. Th=
e
>>> =C2=A0=C2=A0 current solution there is to use the shost sdev request =
queue, which
>>> =C2=A0=C2=A0 isn't great.
>>> This series changes the ata port probe to alloc the sdev in the
>>> ata_device revalidation, and then just do a SCSI starget scan=20
>>> afterwards.
>>>
>>> Why an RFC?
>>> 1. IPR=C2=A0 driver needs to be fixed up - it does not use ATA EH por=
t probe
>>> =C2=A0=C2=A0=C2=A0 Mail [1] needs following up
>>
>> Yes. If IPR could be converted to ata error_handler, a lot of code can=
=20
>> be simplified in libata too.
>=20
> Hmmm... yeah, it would be good to see progress there.
>=20
>>
>>> 2. SATA PMP support needs verification, but I don't have a setup
>>
>> Port multiplier behind a sas HBA will be challenging to setup :)
>> I can try, but I will need to open up one of my servers and hook a=20
>> small PMP box to one of the pm8001 plugs. I may have the cables for=20
>> that... Let me check.
>=20
> I was more thinking of just AHCI with a port multiplier.

OK. I got confused :)
Easy then, my test box is all hooked up already.
Will give this a spin.

>=20
> As for SAS controllers, I don't think it's something to be concerned=20
> about. For a start, I know for sure that hisi_sas HW does not support=20
> port multipliers, and I don't think that pm8001 does either. In=20
> addition, libsas does not even support it - I did see a series in the=20
> scsi list from years ago (to support it), but it did not progress.
>=20
> Thanks,
> John

--=20
Damien Le Moal
Western Digital Research