Messages in this thread | | | Date | Mon, 21 Apr 2014 09:38:01 -0400 | From | Santosh Shilimkar <> | Subject | Re: [PATCH v2 5/7] ARM: dma: Use dma_pfn_offset for dma address translation |
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On Saturday 19 April 2014 03:43 PM, Russell King - ARM Linux wrote: > On Sat, Apr 19, 2014 at 10:32:50AM -0400, Santosh Shilimkar wrote: >> From: Grygorii Strashko <grygorii.strashko@ti.com> >> >> In most of cases DMA addresses can be performed using offset value of >> Bus address space relatively to physical address space as following: >> >> PFN->DMA: >> __pfn_to_phys(pfn + [-]dma_pfn_offset) >> >> DMA->PFN: >> __phys_to_pfn(dma_addr) + [-]dma_pfn_offset >> >> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >> Cc: Russell King <linux@arm.linux.org.uk> >> Cc: Arnd Bergmann <arnd@arndb.de> >> Cc: Olof Johansson <olof@lixom.net> >> Cc: Grant Likely <grant.likely@linaro.org> >> Cc: Rob Herring <robh+dt@kernel.org> >> Cc: Catalin Marinas <catalin.marinas@arm.com> >> Cc: Linus Walleij <linus.walleij@linaro.org> >> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com> >> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com> >> --- >> arch/arm/include/asm/dma-mapping.h | 17 +++++++++++++---- >> 1 file changed, 13 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h >> index e701a4d..8c12149 100644 >> --- a/arch/arm/include/asm/dma-mapping.h >> +++ b/arch/arm/include/asm/dma-mapping.h >> @@ -58,22 +58,31 @@ static inline int dma_set_mask(struct device *dev, u64 mask) >> #ifndef __arch_pfn_to_dma >> static inline dma_addr_t pfn_to_dma(struct device *dev, unsigned long pfn) >> { >> - return (dma_addr_t)__pfn_to_bus(pfn); >> + if (!dev) >> + return DMA_ERROR_CODE; >> + return (dma_addr_t)__pfn_to_bus(pfn - dev->dma_pfn_offset); > > How do ISA devices (iow, those which pass a NULL device) work with this? > This looks to me like it ends up breaking some drivers. > > I've also seen some drivers (such as the Freescale FEC driver) which > perform DMA coherent allocations with a NULL device - technically, that's > a bug in the driver, but the above change will cause them to regress. > Good point. We can keep the NULL case working as well...
static inline dma_addr_t pfn_to_dma(struct device *dev, unsigned long pfn) {
if (!dev) return (dma_addr_t)__pfn_to_bus(pfn); else return (dma_addr_t)__pfn_to_bus(pfn - dev->dma_pfn_offset); }
I will update the patch accordingly.
Regards, Santosh
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