linux-kernel - Re: [PATCH 01/16] hpsa: do readl after writel in main i/o path to ensure commands don't get lost.

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Message-ID: <20110504125212.GC5997@beardog.cce.hp.com>
Date:	Wed, 4 May 2011 07:52:12 -0500
From:	scameron@...rdog.cce.hp.com
To:	Tomas Henzl <thenzl@...hat.com>
Cc:	james.bottomley@...senpartnership.com, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, smcameron@...oo.com,
	akpm@...ux-foundation.org, mikem@...rdog.cce.hp.com,
	scameron@...rdog.cce.hp.com
Subject: Re: [PATCH 01/16] hpsa: do readl after writel in main i/o path to ensure	commands don't get lost.

On Wed, May 04, 2011 at 01:15:50PM +0200, Tomas Henzl wrote:
> On 05/03/2011 09:58 PM, Stephen M. Cameron wrote:
> > From: Stephen M. Cameron <scameron@...rdog.cce.hp.com>
> >
> > Apparently we've been doin it rong for a decade, but only lately do we
> > run into problems.
> >
> > Signed-off-by: Stephen M. Cameron <scameron@...rdog.cce.hp.com>
> > ---
> >  drivers/scsi/hpsa.h |    1 +
> >  1 files changed, 1 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h
> > index 621a153..98c97ca 100644
> > --- a/drivers/scsi/hpsa.h
> > +++ b/drivers/scsi/hpsa.h
> > @@ -212,6 +212,7 @@ 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);
> >   
> Hi,
> a small nit -
> the (void) ^ is I think not needed for gcc and isn't present in the cciss.h patch

I just put it there to make it clear that it ignoring the return of readl is 
done intentionally, not accidentally.  If this goes against some coding convention,
whatever, I'm not super attached to the (void), but I did put it there on purpose,
and would have done it in cciss as well, had I thought of it at the time.

-- steve

> 
> Tomas
> 
> >  	h->commands_outstanding++;
> >  	if (h->commands_outstanding > h->max_outstanding)
> >  		h->max_outstanding = h->commands_outstanding;
> >
> > --
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> >   
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