Re: [PATCH 6/7] ARM: use the common dma_to_phys/phys_to_dma implementation where possible

From: Christoph Hellwig <hch@lst.de>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>,
	Russell King <linux@armlinux.org.uk>,
	Linus Walleij <linus.walleij@linaro.org>,
	Andre Przywara <andre.przywara@arm.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Gregory Clement <gregory.clement@bootlin.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	Laurentiu Tudor <laurentiu.tudor@nxp.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	"open list:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	USB list <linux-usb@vger.kernel.org>
Subject: Re: [PATCH 6/7] ARM: use the common dma_to_phys/phys_to_dma implementation where possible
Date: Thu, 21 Apr 2022 16:12:29 +0200	[thread overview]
Message-ID: <20220421141229.GB20492@lst.de> (raw)
In-Reply-To: <CAK8P3a3BD5zLiXf=Wr0kcJp-k3+vmhBkEP5DNRw_-H=OX9CoGA@mail.gmail.com>

On Thu, Apr 21, 2022 at 10:05:11AM +0200, Arnd Bergmann wrote:
> > -unsigned long __pfn_to_bus(unsigned long pfn)
> > +#else
> > +static inline unsigned long fb_bus_sdram_offset(void)
> >  {
> > -       return __pfn_to_phys(pfn) + (fb_bus_sdram_offset() - PHYS_OFFSET);
> > +       return BUS_OFFSET;
> >  }
> > -EXPORT_SYMBOL(__pfn_to_bus);
> > +#endif /* CONFIG_FOOTBRIDGE_ADDIN */
> 
> I have an older patch to remove CONFIG_FOOTBRIDGE_ADDIN
> completely, as it does a couple of other nasty things and there are
> apparently no users. Would that help here?

For this series it doesn't really make much of a difference.  The addin
case actually is simpler than the host mode for DMA,  But overall
CONFIG_FOOTBRIDGE_ADDIN seems to be a collection of special cases, so
if it is unused and can be remove that would probably be a good thing.

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