Make bus_dmamem_alloc(9) recognize the BUS_DMA_64BIT flag and interpret

it as a request for memory without any DMA restrictions, which means that
the call is allowed to allocate memory above the 4GB boundary on amd64.

ok mpi@, mlarkin@

diff --git a/sys/arch/amd64/amd64/bus_dma.c b/sys/arch/amd64/amd64/bus_dma.c
index 56c750e..465401f 100644 (file)
--- a/sys/arch/amd64/amd64/bus_dma.c
+++ b/sys/arch/amd64/amd64/bus_dma.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: bus_dma.c,v 1.58 2024/08/28 18:21:15 bluhm Exp $      */
+/*     $OpenBSD: bus_dma.c,v 1.59 2024/10/08 19:40:00 kettenis Exp $   */
 /*     $NetBSD: bus_dma.c,v 1.3 2003/05/07 21:33:58 fvdl Exp $ */
 
 /*-
@@ -537,15 +537,18 @@ _bus_dmamem_alloc(bus_dma_tag_t t, bus_size_t size, bus_size_t alignment,
     bus_size_t boundary, bus_dma_segment_t *segs, int nsegs, int *rsegs,
     int flags)
 {
+       paddr_t low, high;
+
+       if (flags & BUS_DMA_64BIT) {
+               low = no_constraint.ucr_low;
+               high = no_constraint.ucr_high;
+       } else {
+               low = dma_constraint.ucr_low;
+               high = dma_constraint.ucr_high;
+       }
 
-       /*
-        * XXX in the presence of decent (working) iommus and bouncebuffers
-        * we can then fallback this allocation to a range of { 0, -1 }.
-        * However for now  we err on the side of caution and allocate dma
-        * memory under the 4gig boundary.
-        */
-       return (_bus_dmamem_alloc_range(t, size, alignment, boundary,
-           segs, nsegs, rsegs, flags, (bus_addr_t)0, (bus_addr_t)0xffffffff));
+       return _bus_dmamem_alloc_range(t, size, alignment, boundary,
+           segs, nsegs, rsegs, flags, low, high);
 }
 
 /*