MIPS: PowerTV: Use O(1) algorthm for phys_to_dma/dma_to_phys

Replace phys_to_dma()/dma_to_phys() looping algorithm with an O(1) algorithm
The approach taken is inspired by the sparse memory implementation: take a
certain number of high-order bits off the address them, use this as an
index into a table containing an offset to the desired address and add
it to the original value. There is a table for mapping physical addresses
to DMA addresses and another one for the reverse mapping. The table sizes
depend on how fine-grained the mappings need to be; Coarser granularity
less to smaller tables.  On a processor with 32-bit physical and DMA
addresses, with 4 MIB granularity, memory usage is two 2048-byte arrays.
Each 32-byte cache line thus covers 64 MiB of address space.

Also, renames phys_to_bus() to phys_to_dma() and bus_to_phys() to
dma_to_phys() to align with kernel usage.

[Ralf: Fixed silly build breakage due to stackoverflow warning caused by
huge array on stack.]

Signed-off-by: David VomLehn <dvomlehn@cisco.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1257/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/mips/include/asm/mach-powertv/dma-coherence.h b/arch/mips/include/asm/mach-powertv/dma-coherence.h
index 5b8d5eb..f76029c 100644
--- a/arch/mips/include/asm/mach-powertv/dma-coherence.h
+++ b/arch/mips/include/asm/mach-powertv/dma-coherence.h
@@ -65,21 +65,21 @@ static inline dma_addr_t plat_map_dma_mem(struct device *dev, void *addr,
 	size_t size)
 {
 	if (is_kseg2(addr))
-		return phys_to_bus(virt_to_phys_from_pte(addr));
+		return phys_to_dma(virt_to_phys_from_pte(addr));
 	else
-		return phys_to_bus(virt_to_phys(addr));
+		return phys_to_dma(virt_to_phys(addr));
 }
 
 static inline dma_addr_t plat_map_dma_mem_page(struct device *dev,
 	struct page *page)
 {
-	return phys_to_bus(page_to_phys(page));
+	return phys_to_dma(page_to_phys(page));
 }
 
 static inline unsigned long plat_dma_addr_to_phys(struct device *dev,
 	dma_addr_t dma_addr)
 {
-	return bus_to_phys(dma_addr);
+	return dma_to_phys(dma_addr);
 }
 
 static inline void plat_unmap_dma_mem(struct device *dev, dma_addr_t dma_addr,