Date: Mon, 20 Jan 2014 13:28:29 +0000
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Vinod Koul <vinod.koul@intel.com>
Cc: Jonas Jensen <jonas.jensen@gmail.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        arm@kernel.org, dan.j.williams@intel.com
Subject: Re: [PATCH] dma: fix vchan_cookie_complete() debug print
Message-ID: <20140120132829.GD15937@n2100.arm.linux.org.uk>
References: <1386344529-25617-1-git-send-email-jonas.jensen@gmail.com> <20140120095917.GZ26823@intel.com> <20140120112822.GA15937@n2100.arm.linux.org.uk> <20140120120301.GE26823@intel.com>
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On Mon, Jan 20, 2014 at 05:33:01PM +0530, Vinod Koul wrote:
> On Mon, Jan 20, 2014 at 11:28:22AM +0000, Russell King - ARM Linux wrote:
> > On Mon, Jan 20, 2014 at 03:29:17PM +0530, Vinod Koul wrote:
> > > On Fri, Dec 06, 2013 at 04:42:09PM +0100, Jonas Jensen wrote:
> > > > vd->tx.cookie is set zero on dma_cookie_complete(),
> > > > save to local before printing it.
> > > > 
> > > > Signed-off-by: Jonas Jensen <jonas.jensen@gmail.com>
> > > > ---
> > > > 
> > > > Notes:
> > > >     dev_vdbg() could also be moved to happen earlier, what do you prefer?
> > > This would be preferred IMHO. Also pls cc dmaengine@vger on this
> > 
> > I prefer this version - it means that the verbose debug printk doesn't
> > impact the completion timing when printk is expensive (eg, because its
> > outputting via a serial port.)
> But if you know your printk is costly, do you want to enable these?

dev_vdbg() is for verbose debugging - you only enable it if you really
need to.  Even so, it should have _minimal_ impact where possible.  That's
why I prefer the first patch, because we mark the cookie as being
complete _before_ we call the verbose debugging, which isn't going to add
milliseconds to that.

If you don't care about debugging, then getting rid of the dev_vdbg().
But really, I could pull rank and say that this is *my* file, I get to
choose how stuff should be done here - I'd prefer not to but...

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