RE: Sample implementation of a scheme to handle missing interrupts

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Mon, 2008-07-28 at 13:01 -0600, Moore, Eric wrote:
> On Sunday, July 27, 2008 11:56 PM, Matthew Wilcox wrote:
> 
> > There has been some discussion recently (both on the mailing
> > list and at
> > OLS) of MSI and it reminded me of a perennial problem that I have with
> > sym2.  When interrupts don't work, I often get the bug
> > reports, because
> > the user seems sym2 spewing error messages right before the panic when
> > it fails to mount their root filesystem.
> >
> 
> In my case, the MSI problem will manifest itself well before we bind
> with the scsi midlayer.    Meaning when there is a MSI problem, we
> can't even bring up the card.  Hence adding code in a eh_timed_out
> callback handler would be meaningless in solving our problem. What I
> need to do is find a problematic card, so I can verify some things.

Actually, you don't need this.  I verified the behaviour of the MSI
problem simply by commenting out the request_irq.  It looks like there's
no simple way to simulate MSI misrouting, but perhaps I should look at
that, since it would be useful.

>    My beliefs are that all the doorbell request at driver load time
> work becuase we are polling with interrupts masked.

This is the actual bug report:

http://bugzilla.kernel.org/show_bug.cgi?id=11045

>   The first command sent with interrupts enabled would be
> SendPortEnable.  If we have a timeout after calling
> mpt_handshake_req_reply_wait, we resend the port enable with MSI
> turned off, right?

James