ARM: DMA-API: better handing of DMA masks for coherent allocations

We need to start treating DMA masks as something which is specific to
the bus that the device resides on, otherwise we're going to hit all
sorts of nasty issues with LPAE and 32-bit DMA controllers in >32-bit
systems, where memory is offset from PFN 0.

In order to start doing this, we convert the DMA mask to a PFN using
the device specific dma_to_pfn() macro.  This is the reverse of the
pfn_to_dma() macro which is used to get the DMA address for the device.

This gives us a PFN mask, which we can then check against the PFN
limit of the DMA zone.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index febaee7ca57b..8aab24f35a5e 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -218,6 +218,7 @@ EXPORT_SYMBOL(arm_dma_zone_size);
  * so a successful GFP_DMA allocation will always satisfy this.
  */
 phys_addr_t arm_dma_limit;
+unsigned long arm_dma_pfn_limit;
 
 static void __init arm_adjust_dma_zone(unsigned long *size, unsigned long *hole,
         unsigned long dma_size)
@@ -240,6 +241,7 @@ void __init setup_dma_zone(const struct machine_desc *mdesc)
                 arm_dma_limit = PHYS_OFFSET + arm_dma_zone_size - 1;
         } else
                 arm_dma_limit = 0xffffffff;
+        arm_dma_pfn_limit = arm_dma_limit >> PAGE_SHIFT;
 #endif
 }