Re: [PATCH] hpsa: do not attempt to read from a write-only register

[scameron@beardog.cce.hp.com]

On Mon, Jul 11, 2011 at 02:04:50PM -0700, Andrew Morton wrote:
> On Mon, 11 Jul 2011 15:51:24 -0500
> scameron@beardog.cce.hp.com wrote:
> 
> > On Mon, Jul 11, 2011 at 01:19:11PM -0700, Andrew Morton wrote:
> > > On Fri, 08 Jul 2011 14:59:26 -0500
> > > "Stephen M. Cameron" <scameron@beardog.cce.hp.com> wrote:
> > > 
> > > > From: Stephen M. Cameron <scameron@beardog.cce.hp.com>
> > > > 
> > > > Most smartarrays tolerate it, but a few new ones don't.
> > > > 
> > > > Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
> > > > ---
> > > >  drivers/scsi/hpsa.h |    2 +-
> > > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > > > 
> > > > diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h
> > > > index 6d8dcd4..7f53cea 100644
> > > > --- a/drivers/scsi/hpsa.h
> > > > +++ b/drivers/scsi/hpsa.h
> > > > @@ -214,7 +214,7 @@ static void SA5_submit_command(struct ctlr_info *h,
> > > >  	dev_dbg(&h->pdev->dev, "Sending %x, tag = %x\n", c->busaddr,
> > > >  		c->Header.Tag.lower);
> > > >  	writel(c->busaddr, h->vaddr + SA5_REQUEST_PORT_OFFSET);
> > > > -	(void) readl(h->vaddr + SA5_REQUEST_PORT_OFFSET);
> > > > +	(void) readl(h->vaddr + SA5_SCRATCHPAD_OFFSET);
> > > >  	h->commands_outstanding++;
> > > >  	if (h->commands_outstanding > h->max_outstanding)
> > > >  		h->max_outstanding = h->commands_outstanding;
> > > 
> > > The changelog forgot to tell us the user-visible effects of the bug. 
> > > That was really really bad of it.  Bad changelog.  No bone for you.
> > 
> > Oh, sorry.  When the controller doesn't tolerate the bug, the firmware
> > on it locks up.  No interrupts are received, no commands complete. I/o
> > on that controller grinds to a halt.
> 
> OK, that was important.
> 
> Presumably you'd like those newer controllers to work with older
> kernels?  In which case we should mark the patch for -stable
> backporting?

Yes.

> 
> I've done that to my copy and have updated the changelog.
> 
> > I can resubmit if you like.
> 
> I have two other needed-in-3.0 scsi patches.  I'll send all three
> Jameswards now.