[src/trunk]: src/sys/external/bsd/drm2/dist/drm/radeon Fix ordering of bus_dm...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d09a1ff32a4d
branches:  trunk
changeset: 834327:d09a1ff32a4d
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Wed Aug 08 22:16:49 2018 +0000

description:
Fix ordering of bus_dmamap_sync.

The ordering is:

...
- driver writes to kernel pointer
- sync
- driver triggers device use of newly written data (*)
- sync
- driver writes to kernel pointer
- sync
...

The operation (*) is a DMA write.  Hence the syncs should be:

...
- driver writes to kernel pointer
- bus_dmamap_sync(BUS_DMASYNC_PREWRITE)
- driver triggers device use of newly written data
- bus_dmamap_sync(BUS_DMASYNC_POSTWRITE)
- bus_dmamap_sync(BUS_DMASYNC_PREWRITE)
- driver writes to kernel pointer
- bus_dmamap_sync(BUS_DMASYNC_POSTWRITE)
- bus_dmamap_sync(BUS_DMASYNC_PREWRITE)
...

(Preemptive pullup from my DRM/KMS update branch in Git.)

XXX pullup-7
XXX pullup-8

diffstat:

 sys/external/bsd/drm2/dist/drm/radeon/radeon_gart.c |  4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diffs (21 lines):

diff -r 94272597ebe5 -r d09a1ff32a4d sys/external/bsd/drm2/dist/drm/radeon/radeon_gart.c
--- a/sys/external/bsd/drm2/dist/drm/radeon/radeon_gart.c       Wed Aug 08 21:17:46 2018 +0000
+++ b/sys/external/bsd/drm2/dist/drm/radeon/radeon_gart.c       Wed Aug 08 22:16:49 2018 +0000
@@ -268,7 +268,7 @@
 
                bus_dmamap_sync(rdev->ddev->dmat, rdev->gart.rg_table_map,
                    gpu_pgstart*entsize, gpu_npages*entsize,
-                   BUS_DMASYNC_PREWRITE);
+                   BUS_DMASYNC_POSTWRITE);
        }
 }
 
@@ -284,7 +284,7 @@
 
                bus_dmamap_sync(rdev->ddev->dmat, rdev->gart.rg_table_map,
                    gpu_pgstart*entsize, gpu_npages*entsize,
-                   BUS_DMASYNC_POSTWRITE);
+                   BUS_DMASYNC_PREWRITE);
        }
        radeon_gart_tlb_flush(rdev);
 }