Re: [PATCH v2 1/7] ARM: mm: Introduce archdata.dma_pfn_offset

On Thursday 27 February 2014 16:17:46 Santosh Shilimkar wrote:

From: Grygorii Strashko <redacted>

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

This patch introduces new field dma_pfn_offset in ARM dev_archdata
structure which has to be filed per-device at arch init time
(simplest way is to use Platform bus notifier to handle
BUS_NOTIFY_ADD_DEVICE event) and updates DMA address translation
routines in order to accommodate bus offset value by default.

Cc: Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
Cc: Arnd Bergmann <redacted>
Cc: Olof Johansson <redacted>
Signed-off-by: Grygorii Strashko <redacted>
Signed-off-by: Santosh Shilimkar <redacted>

This was my suggestion, and the implementation is trivial, so

Acked-by: Arnd Bergmann <redacted>

This should be most of what LinusW needs to generalize the
mach-integrator PCI DMA mapping.
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