linux-kernel - Re: [PATCH v3 5/7] ARM: dma: Use dma_pfn

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Date:	Mon, 5 May 2014 20:50:40 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org,
	Grygorii Strashko <grygorii.strashko@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v3 5/7] ARM: dma: Use dma_pfn_offset for dma address
	translation

On Fri, May 02, 2014 at 11:05:16AM -0400, Santosh Shilimkar wrote:
> On Friday 02 May 2014 10:58 AM, Russell King - ARM Linux wrote:
> > On Thu, Apr 24, 2014 at 11:30:05AM -0400, Santosh Shilimkar wrote:
> >>  static inline void *dma_to_virt(struct device *dev, dma_addr_t addr)
> >>  {
> >> -	return (void *)__bus_to_virt((unsigned long)addr);
> >> +	if (!dev)
> >> +		return (void *)__bus_to_virt((unsigned long)addr);
> >> +	else
> >> +		return (void *)__bus_to_virt(__pfn_to_bus(dma_to_pfn(dev, addr)));
> > 
> > This is quite horrendous.  There's easier ways to do this...  I assume
> > you haven't looked at the assembler resulting from this at all with
> > stuff like the p2v patching enabled?
> > 
> I haven't. Will check.

	if (dev) {
		unsigned long pfn = dma_to_pfn(dev, addr);

		return phys_to_virt(__pfn_to_phys(pfn));
	}

	return (void *)__bus_to_virt((unsigned long)addr);

> >>  static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
> >>  {
> >> -	return (dma_addr_t)__virt_to_bus((unsigned long)(addr));
> >> +	if (!dev)
> >> +		return (dma_addr_t)__virt_to_bus((unsigned long)(addr));
> >> +	else
> >> +		return pfn_to_dma(dev,
> >> +				__bus_to_pfn(__virt_to_bus((unsigned long)(addr))));
> > 
> > Same here.
> > 
> ok.


	if (dev)
		return pfn_to_dma(dev, virt_to_pfn(addr));

	return (dma_addr_t)__virt_to_bus((unsigned long)(addr));

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