linux-kernel - Re: [PATCH 6/7] ARM: use the common dma_to_phys/phys_to

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Message-ID: <20220421141229.GB20492@lst.de>
Date:   Thu, 21 Apr 2022 16:12:29 +0200
From:   Christoph Hellwig <hch@....de>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Christoph Hellwig <hch@....de>,
        Russell King <linux@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andre Przywara <andre.przywara@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 6/7] ARM: use the common dma_to_phys/phys_to_dma
 implementation where possible

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.