linux-kernel - Re: [V4 PATCH 3/6] pci: Generic function for setting up PCI device DMA coherency

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Message-ID: <20150520093401.GC25313@e104818-lin.cambridge.arm.com>
Date:	Wed, 20 May 2015 10:34:01 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org, linaro-acpi@...ts.linaro.org,
	will.deacon@....com, herbert@...dor.apana.org.au,
	al.stone@...aro.org, linux-acpi@...r.kernel.org,
	Murali Karicheri <m-karicheri2@...com>, msalter@...hat.com,
	grant.likely@...aro.org, hanjun.guo@...aro.org,
	thomas.lendacky@....com, Rob Herring <robh+dt@...nel.org>,
	bhelgaas@...gle.com, netdev@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, leo.duran@....com,
	linux-crypto@...r.kernel.org,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	lenb@...nel.org, David Woodhouse <dwmw2@...radead.org>,
	davem@...emloft.net
Subject: Re: [V4 PATCH 3/6] pci: Generic function for setting up PCI device
 DMA coherency

On Wed, May 20, 2015 at 11:27:54AM +0200, Arnd Bergmann wrote:
> On Wednesday 20 May 2015 10:24:15 Catalin Marinas wrote:
> > On Sat, May 16, 2015 at 01:59:00AM +0200, Rafael J. Wysocki wrote:
> > > On Friday, May 15, 2015 04:23:11 PM Suravee Suthikulpanit wrote:
> > > > +/**
> > > > + * pci_dma_configure - Setup DMA configuration
> > > > + * @pci_dev: ptr to pci_dev struct of the PCI device
> > > > + *
> > > > + * Function to update PCI devices's DMA configuration using the same
> > > > + * info from the OF node or ACPI node of host bridge's parent (if any).
> > > > + */
> > > > +static void pci_dma_configure(struct pci_dev *pci_dev)
> > > > +{
> > > > +   struct device *dev = &pci_dev->dev;
> > > > +   struct device *bridge = pci_get_host_bridge_device(pci_dev);
> > > > +   struct device *host = bridge->parent;
> > > > +   struct acpi_device *adev;
> > > > +
> > > > +   if (!host)
> > > > +           return;
> > > > +
> > > > +   if (acpi_disabled) {
> > > > +           of_dma_configure(dev, host->of_node);
> > > 
> > > I'd rather do
> > > 
> > >       if (IS_ENABLED(CONFIG_OF) && host->of_node) {
> > >               of_dma_configure(dev, host->of_node);
> > 
> > Nitpick: do we need the CONFIG_OF check? If disabled, I don't think
> > anyone would set host->of_node.
> 
> If of_dma_configure() is defined in a file that is built conditionally
> based on CONFIG_OF, you need it.

We have a dummy of_dma_configure() already when !CONFIG_OF, otherwise
we would need #ifndef here. I already replied, I think for other
architectures we need this check to avoid a useless host->of_node test.

-- 
Catalin
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