netdev - Re: [RFC 0/7] Fixing dma mask setting in various network drivers

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Message-ID: <20130617204505.GT2718@n2100.arm.linux.org.uk>
Date:	Mon, 17 Jun 2013 21:45:05 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Alex Duyck <alexander.h.duyck@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Carolyn Wyborny <carolyn.wyborny@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	e1000-devel@...ts.sourceforge.net,
	Greg Rose <gregory.v.rose@...el.com>,
	John Ronciak <john.ronciak@...el.com>, netdev@...r.kernel.org,
	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>,
	Rasesh Mody <rmody@...cade.com>,
	Tushar Dave <tushar.n.dave@...el.com>
Subject: Re: [RFC 0/7] Fixing dma mask setting in various network drivers

On Mon, Jun 17, 2013 at 01:35:41PM -0700, Jeff Kirsher wrote:
> On Mon, 2013-06-17 at 15:01 +0100, Russell King - ARM Linux wrote:
> > On Tue, Jun 11, 2013 at 11:12:30AM -0700, Jesse Brandeburg wrote:
> > > This is my proposed change to the intel drivers.  Comments?
> > > 
> > > +	if (!dma_set_mask(&pdev->dev, DMA_BIT_MASK(64))) {
> > > +		pci_using_dac = true;
> > > +		/* coherent mask for the same size will always succeed if
> > > +		 * dma_set_mask does
> > > +		 */
> > > +		dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(64));
> > > +	} else if (!dma_set_mask(&pdev->dev, DMA_BIT_MASK(32))) {
> > > +		pci_using_dac = false;
> > > +		dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32));
> > > +	} else {
> > > +		dev_err(&pdev->dev, "%s: DMA configuration failed: %d\n",
> > > +			 __func__, err);
> > > +		err = -EIO;
> > > +		goto err_dma;
> > >  	}
> > > 
> > 
> > So, will you be going with this change rather than mine, which apparantly
> > Jeff queued?  Please let me know what you decide so I can keep my private
> > git tree in sync with what you've decided to avoid conflicting with
> > further dma-mask changes which I'm working on.
> > 
> > Thanks.
> 
> I thought the kernel helper function dma_set_mask_and_coherent(...) was
> the best solution.
> 
> I dropped your original series of patches from my queue since it
> appeared that there was a better alternative to this solution.

Such a helper doesn't exist yet, and I'm not sure these changes should
wait for that.  Hmm, okay, it's probably too late in the -rc cycle
anyway for these changes now.

I'll respin them according to Jesse's patch above, but as I have already
mentioned, this will be part of a much larger series, and I was hoping
to get those trivial fixes in for 3.10 to avoid that kind of dependency.
Instead, they'll be stuck at the bottom of a much larger series, which
will depend on these changes.  Bah.
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