kern/164694: Regression in 3726 port multiplier support in 9.0

[Allen Belletti]

The following reply was made to PR kern/164694; it has been noted by GNATS.

From: Allen Belletti <allen at gtf.org>
To: bug-followup at freebsd.org
Cc:  
Subject: Re: kern/164694: Regression in 3726 port multiplier support in 9.0
Date: Thu, 02 Feb 2012 13:08:13 -0500

 I've reached a dead end but come up with a few more bits of information. 
   It's definitely some sort of irq setup/handling problem.  I 
 experimented with setting hint.siis.X.msi=1 for these cards. 
 Surprisingly, they almost seem to work.  They're able to immediately 
 detect the pmp device and recognize the four disks on the other side of 
 it.  However, after a few seconds of I/O, it'll get stuck and time out. 
   Presumably MSI just doesn't work on these cards which is why it 
 defaults to disabled (I've seen hints of problems like that in my 
 search.)  I did also try forcing hint.siisch.X.sata_rev=1 but it didn't 
 seem to improve the situation, which makes sense if it's fundamentally 
 an interrupt handling problem.
 
 It's unlikely that I can get any further on my own, but it seems likely 
 that some sort of IRQ handling problem was introduced between 8.2 and 9.0.
 
 Thanks,
 Allen