device: introduce per device dma_pfn_offset
On few architectures, there are few restrictions on DMAble area of system
RAM. That also means that devices needs to know about this restrictions so
that the dma_masks can be updated accordingly and dma address translation
helpers can add/subtract the dma offset.
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
So we introduce per device dma_pfn_offset which can be popullated
by architecture init code while creating the devices.
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: Catalin Marinas <catalin.marinas@arm.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
1 file changed