[Mesa-dev] [PATCH] i965: Combine URB code emission into a single group.

[Kenneth Graunke]

All four URB packets need to be programmed together in order for the GPU
state to be valid.  Putting them in separate BEGIN..ADVANCE blocks is
risky: if we're nearing the end of a batch, the batch could be flushed
inbetween two of the commands, causing the URB programming to be split
into two batchbuffers.

This -might- be okay with hardware contexts, but it offers no advantages
over keeping them together, and has a potential for hangs.

Putting them into a single BEGIN..ADVANCE block ensures they'll be kept
in the same batch, which seems wise.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/gen7_urb.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/gen7_urb.c b/src/mesa/drivers/dri/i965/gen7_urb.c
index ce01dda..350f644 100644
--- a/src/mesa/drivers/dri/i965/gen7_urb.c
+++ b/src/mesa/drivers/dri/i965/gen7_urb.c
@@ -60,12 +60,10 @@ gen7_allocate_push_constants(struct brw_context *brw)
    if (brw->is_haswell && brw->gt == 3)
       size = 16;
 
-   BEGIN_BATCH(2);
+   BEGIN_BATCH(4);
    OUT_BATCH(_3DSTATE_PUSH_CONSTANT_ALLOC_VS << 16 | (2 - 2));
    OUT_BATCH(size);
-   ADVANCE_BATCH();
 
-   BEGIN_BATCH(2);
    OUT_BATCH(_3DSTATE_PUSH_CONSTANT_ALLOC_PS << 16 | (2 - 2));
    OUT_BATCH(size | size << GEN7_PUSH_CONSTANT_BUFFER_OFFSET_SHIFT);
    ADVANCE_BATCH();
@@ -105,27 +103,21 @@ void
 gen7_emit_urb_state(struct brw_context *brw, GLuint nr_vs_entries,
                     GLuint vs_size, GLuint vs_start)
 {
-   BEGIN_BATCH(2);
+   BEGIN_BATCH(8);
    OUT_BATCH(_3DSTATE_URB_VS << 16 | (2 - 2));
    OUT_BATCH(nr_vs_entries |
              ((vs_size - 1) << GEN7_URB_ENTRY_SIZE_SHIFT) |
              (vs_start << GEN7_URB_STARTING_ADDRESS_SHIFT));
-   ADVANCE_BATCH();
 
    /* Allocate the GS, HS, and DS zero space - we don't use them. */
-   BEGIN_BATCH(2);
    OUT_BATCH(_3DSTATE_URB_GS << 16 | (2 - 2));
    OUT_BATCH((0 << GEN7_URB_ENTRY_SIZE_SHIFT) |
              (vs_start << GEN7_URB_STARTING_ADDRESS_SHIFT));
-   ADVANCE_BATCH();
 
-   BEGIN_BATCH(2);
    OUT_BATCH(_3DSTATE_URB_HS << 16 | (2 - 2));
    OUT_BATCH((0 << GEN7_URB_ENTRY_SIZE_SHIFT) |
              (vs_start << GEN7_URB_STARTING_ADDRESS_SHIFT));
-   ADVANCE_BATCH();
 
-   BEGIN_BATCH(2);
    OUT_BATCH(_3DSTATE_URB_DS << 16 | (2 - 2));
    OUT_BATCH((0 << GEN7_URB_ENTRY_SIZE_SHIFT) |
              (vs_start << GEN7_URB_STARTING_ADDRESS_SHIFT));
-- 
1.8.3.2