[PATCH V3] of: Set the DMA mask to 64 bits when dma_addr_t is 64-bits

[lauraa@codeaurora.org (Laura Abbott)]

On 7/8/2013 3:42 AM, Russell King - ARM Linux wrote:
>>
>> The problem is the way the arm_dma_limit is set up, all dma allocations
>> are currently broken regardless of if the actual device supports 64-bit
>> addresses or not.
>
> Please explain this statement.
>

The statement was a bit shortsighted given recent discussions. My point 
was that on LPAE systems right now without ZONE_DMA, the allocation 
fails by default (i.e. no call to set_mask) even if the device could 
support 64-bit physical memory. Based on this thread though, drivers 
should stop assuming the dma_mask will be set up properly and always set 
the mask appropriately.

The conclusion also seems to be that if devices on an LPAE system can't 
handle > 32-bit addresses and want to limit via mask, ZONE_DMA must be 
set up.

Please correct me if I misunderstood anything.

Thanks,
Laura

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