[PATCH] powerpc/powernv: Turn on SCSI_AACRAID in powernv_defconfig

[Brian King]

On 08/31/2017 07:37 AM, Michael Ellerman wrote:
> Stewart Smith <stewart at linux.vnet.ibm.com> writes:
> 
>> Michael Ellerman <mpe at ellerman.id.au> writes:
>>> OK. So maybe when the petitboot kernel moves up to 4.14 they may want to
>>> flip it back to being a module.
>>
>> Yeah. We tend to keep all RAID adapters as modules because they almost
>> all uniquely try to undo all boot time optimization done by anybody,
>> anywhere, ever.
> 
> Yes I know what you mean. I am thinking of one In ParticulaR.

Ouch. In all fairness over the life of ipr I've done a couple things to
improve initialization time.

1. On a PowerVM machine, the ipr boot device should not get reset between
   the FCODE driver and the Linux driver, so init is extremely fast. If its
   a non-boot device, then you'll have to wait for the firmware to initialize
   on those adapters.
2. On a bare metal machine, if you set ipr.fast_reboot=1 on the skiboot
   kernel, then we should also avoid resetting the ipr adapter, so ipr
   init on the kernel being kexec booted from skiboot should be extremely fast. 

As to improving ipr init time in the skiboot kernel, that becomes more
difficult to do safely. The firmware stack still needs to boot, do device
discovery, potentially spin up disks, etc, which all takes time.

Additionally, we put in changes in the firmware and driver to address
complaints largely from Anton about it taking too long for ipr to timeout on
bad adapters.

If you've got cases where ipr init is taking a long time, I'd be
interested to know what scenarios are the most annoying to see if there
is any opportunity to improve.

-Brian

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