From mboxrd@z Thu Jan 1 00:00:00 1970 From: Santosh Shilimkar Subject: Re: [PATCH v2 5/7] ARM: dma: Use dma_pfn_offset for dma address translation Date: Mon, 21 Apr 2014 09:38:01 -0400 Message-ID: <53551F39.90908@ti.com> References: <1397917972-6293-1-git-send-email-santosh.shilimkar@ti.com> <1397917972-6293-6-git-send-email-santosh.shilimkar@ti.com> <20140419194334.GL24070@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140419194334.GL24070-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Russell King - ARM Linux Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Grygorii Strashko , Greg Kroah-Hartman , Arnd Bergmann , Olof Johansson , Grant Likely , Rob Herring , Catalin Marinas , Linus Walleij List-Id: devicetree@vger.kernel.org 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 >> >> 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 >> Cc: Russell King >> Cc: Arnd Bergmann >> Cc: Olof Johansson >> Cc: Grant Likely >> Cc: Rob Herring >> Cc: Catalin Marinas >> Cc: Linus Walleij >> Signed-off-by: Grygorii Strashko >> Signed-off-by: Santosh Shilimkar >> --- >> 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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html