linux-kernel - Re: [PATCH v4 3/3] mmc: sdhci-pci: Do not set DMA mask in enable

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Message-ID: <20160314155211.GC13471@localhost>
Date:	Mon, 14 Mar 2016 10:52:12 -0500
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Alexandre Courbot <acourbot@...dia.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/3] mmc: sdhci-pci: Do not set DMA mask in
 enable_dma()

On Mon, Mar 14, 2016 at 03:00:36PM +0200, Adrian Hunter wrote:
> On 14/03/16 05:15, Alexandre Courbot wrote:
> > On Tue, Mar 8, 2016 at 10:18 PM, Adrian Hunter <adrian.hunter@...el.com> wrote:
> >> On 07/03/16 04:07, Alexandre Courbot wrote:
> >>> DMA mask will already be set by sdhci_set_dma_mask(), which
> >>> is equivalent to the removed code since pci_set_dma_mask()
> >>> expands to its DMA-API counterpart.
> >>>
> >>> There should also be no reason to set the DMA mask after probe.
> >>
> >> Let's run that by the PCI mailing list just to be sure.  The patches for
> >> reference:
> >>
> >>         http://marc.info/?l=linux-mmc&m=145731654328126&w=2
> >>         http://marc.info/?l=linux-mmc&m=145731654328128&w=2
> >>
> >> change the sdhci-pci driver to set the DMA mask once during probe instead of
> >> every time during resume.  Is there any reason a PCI device driver might
> >> need to set the DMA mask every time during resume?
> > 
> > Not seeing much reaction for this patchset. PCI being the only
> > possible point of contention, can we maybe roll it into -next and see
> > what happens?
> 
> +Rafael
> 
> Rafael, can you offer any thoughts on this:
> 
> PCI drivers that want to use DMA might call pci_set_master() in the pm
> resume callback.  Some drivers (like sdhci-pci) also, presumably out of
> convenience, set the DMA mask at the same time.  The question is: is it OK
> instead to set the DMA mask just once during probe, or is there some other
> reason the DMA mask needs to be set every time during resume?

I don't see a reason why the DMA mask would need to be set during
resume.

Bjorn