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, 9 insertions, 9 deletions

diff --git a/arch/mips/powertv/asic/asic_devices.c b/arch/mips/powertv/asic/asic_devices.c
index 9ec523e4dd06..c81dd497ed7b 100644
--- a/arch/mips/powertv/asic/asic_devices.c
+++ b/arch/mips/powertv/asic/asic_devices.c
@@ -80,8 +80,8 @@ static bool usb_configured;
  * Don't recommend to use it directly, it is usually used by kernel internally.
  * Portable code should be using interfaces such as ioremp, dma_map_single, etc.
  */
-unsigned long phys_to_bus_offset;
-EXPORT_SYMBOL(phys_to_bus_offset);
+unsigned long phys_to_dma_offset;
+EXPORT_SYMBOL(phys_to_dma_offset);
 
 /*
  *
@@ -533,10 +533,10 @@ void __init configure_platform(void)
 
         switch (asic) {
         case ASIC_ZEUS:
-                phys_to_bus_offset = 0x30000000;
+                phys_to_dma_offset = 0x30000000;
                 break;
         case ASIC_CALLIOPE:
-                phys_to_bus_offset = 0x10000000;
+                phys_to_dma_offset = 0x10000000;
                 break;
         case ASIC_CRONUSLITE:
                 /* Fall through */
@@ -546,10 +546,10 @@ void __init configure_platform(void)
                  * 0x2XXXXXXX. If 0x10000000 aliases into 0x60000000-
                  * 0x6XXXXXXX, the offset should be 0x50000000, not 0x10000000.
                  */
-                phys_to_bus_offset = 0x10000000;
+                phys_to_dma_offset = 0x10000000;
                 break;
         default:
-                phys_to_bus_offset = 0x00000000;
+                phys_to_dma_offset = 0x00000000;
                 break;
         }
 }
@@ -603,7 +603,7 @@ void __init platform_alloc_bootmem(void)
                 int size = gp_resources[i].end - gp_resources[i].start + 1;
                 if ((gp_resources[i].start != 0) &&
                         ((gp_resources[i].flags & IORESOURCE_MEM) != 0)) {
-                        reserve_bootmem(bus_to_phys(gp_resources[i].start),
+                        reserve_bootmem(dma_to_phys(gp_resources[i].start),
                                 size, 0);
                         total += gp_resources[i].end -
                                 gp_resources[i].start + 1;
@@ -627,7 +627,7 @@ void __init platform_alloc_bootmem(void)
 
                         else {
                                 gp_resources[i].start =
-                                        phys_to_bus(virt_to_phys(mem));
+                                        phys_to_dma(virt_to_phys(mem));
                                 gp_resources[i].end =
                                         gp_resources[i].start + size - 1;
                                 total += size;
@@ -691,7 +691,7 @@ static void __init pmem_setup_resource(void)
         if (resource && pmemaddr && pmemlen) {
                 /* The address provided by bootloader is in kseg0. Convert to
                  * a bus address. */
-                resource->start = phys_to_bus(pmemaddr - 0x80000000);
+                resource->start = phys_to_dma(pmemaddr - 0x80000000);
                 resource->end = resource->start + pmemlen - 1;
 
                 pr_info("persistent memory: start=0x%x  end=0x%x\n",