RE: Do we still need the scsi IPR driver ?

From: Brian King <brking@linux.vnet.ibm.com>
To: Hannes Reinecke <hare@suse.de>,
	John Garry <john.garry@huawei.com>,
	Damien Le Moal <damien.lemoal@opensource.wdc.com>,
	Brian King <brking@us.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org
Subject: RE: Do we still need the scsi IPR driver ?
Date: Wed, 12 Oct 2022 22:36:39 -0500	[thread overview]
Message-ID: <b7c0f38b-b56f-761b-9ce7-7b3d67a564d0@linux.vnet.ibm.com> (raw)
In-Reply-To: <6c1f12d2-9211-85ef-dfd5-e091ea1559d7@suse.de>

On 10/6/22 2:35 AM, Hannes Reinecke wrote:
> On 10/5/22 19:20, Brian King wrote:
>> On 9/20/22 8:07 AM, John Garry wrote:
>>> On 21/06/2022 23:12, Damien Le Moal wrote:
>>>>>> We still need it around for now. IBM still sells these adapters
>>>>>> and they can still be ordered even on our latest Power 10 systems.
>>>>> At one point I did look into modifying ipr to use an ->error_handler.
>>>>> I recall I ran into some issues that resulted in this getting put
>>>>> on the shelf, but its been a while. I'll go dig that code up and
>>>>> see what it looks like.
>>>> Thanks. It would be really great if you can convert to using
>>>> error_handler. This is really the last ata/libsas driver that does not use
>>>> this.
>>>>
>>>
>>> Hi Brian,
>>>
>>> I am wondering if there is any update here?
>>>
>>> As you may have seen in [0], I think that we need to make progress on this topic first to keep the solution there a bit simpler.
>>>
>>> [0] https://lore.kernel.org/linux-scsi/1663669630-21333-1-git-send-email-john.garry@huawei.com/T/#mf890cb4f1627112652831524dca62cbde4a0a637  
>>
>> I've made some progress. I was able to dig up the code to move ipr to use error_handler
>> and have gotten it to compile, but haven't gotten to trying it in the lab yet.
>>
> Hmm. In which machines can I find an IPR installed? I could go hunting in our lab, maybe I can locate one and aid testing/development ...

Any Power 9 or older generation PowerVM based system would have an IPR installed as the boot device.
Additionally, on Power 10 systems, ipr SAS controllers are available as an add in card. 

However, the SATA support in ipr was only used to attach the onboard SATA DVD. Power 8 systems were
the last generation of systems that had an onboard SATA DVD. So, to do any testing with a
SATA DVD, you'd need a Power 8 or older system. 

Right now I have a patch that removes the SATA support from ipr completely and a patch that changes
to use the error_handler libata support. The one that changes to use the error_handler libata API
adds a bit of complexity for a function that should have few or no users that would need this support
on a current upstream kernel, since only Power 8 and older systems use this support. I'm getting
a system setup to try out both patches, but at this point I'm leaning towards the patch that
removes the libata dependency from ipr.

Thanks,

Brian

-- 
Brian King
Power Linux I/O
IBM Linux Technology Center