C FCode Memory Allocation

For OpenBoot 2

To get general-purpose memory, use buffer: or alloc-mem. Use free-mem to deallocate memory obtained with alloc-mem.

To map in portions of your device for ordinary access, use " map-in" $call-parent ( adr space size -- virt ), as in:

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my-address  offset +  my-space  size  " map-in" $call-parent  ( virt )

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To later map out those portions of your device, use " map-out" $call- parent ( virt size -- ), as in:

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( virt )  size  " map-out" $call-parent

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To use a region of system memory for DMA (for example, for both direct CPU access and DMA access from a device), first define the following mapping and allocation routines, then follow the steps below to ensure data coherency.

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: dma-alloc  ( n -- virt )  " dma-alloc" $call-parent  ;
: dma-free  ( virt n -- )    " dma-free" $call-parent  ;
: dma-map-in  ( virt n cache? -- devaddr )  " dma-map-in" $call-parent  ;
: dma-map-out  ( virt devaddr n -- )       " dma-map-out" $call-parent  ;
: dma-sync  ( virt devaddr size -- )  \ Correct even if "dma-sync" missing
   " dma-sync" ['] $call-parent catch  if
      2drop 3drop
   then
;

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1. Allocate the DMA region with:

• dma-alloc

• dma-map-in

2. CPU accesses the region using virt from dma-alloc, then perform:

• dma-sync

3. Start DMA operation, using devaddr from dma-map-in.

• Wait for DMA complete status.

• Repeat DMA as needed, then perform dma-sync

4. Repeat steps 2 and 3 as needed

5. 5) Deallocate the region when completed, with:

• dma-map-out

• dma-free

For OpenBoot 1

To obtain general-purpose memory, use buffer: or alloc-mem for small amounts (less than several hundred bytes). Use dma-alloc for larger amounts.

Use free-mem to deallocate memory allocated with alloc-mem. Use free- virtual to deallocate memory allocated with dma-alloc.

To map in portions of your device for ordinary access, use map-sbus.

To map out portions of your device, use free-virtual.

To use a region of system memory for DMA (for example, both direct CPU access and DMA access from a device), map it in with dma-alloc. CPU accesses and DMA accesses may be performed interchangeably.

When the memory is no longer needed, unmap it with free-virtual.

When unmapping multiple regions using free-virtual, you must perform the unmapping in the reverse order that the memory was originally mapped in.