[Mesa-dev] [PATCH v3] radv: make sure to wait for CP DMA when needed

[Samuel Pitoiset]

This might fix some synchronization issues. I don't know if
that will affect performance but it's required for correctness.

v3: - wait for CP DMA in CmdPipelineBarrier()
    - clear the busy value when CP_DMA_SYNC is requested
v2: - wait for CP DMA in CmdWaitEvents()
    - track if CP DMA is used

CC: <mesa-stable at lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
---
 src/amd/vulkan/radv_cmd_buffer.c | 15 +++++++++++++
 src/amd/vulkan/radv_private.h    |  5 +++++
 src/amd/vulkan/si_cmd_buffer.c   | 36 ++++++++++++++++++++++++++++----
 3 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/src/amd/vulkan/radv_cmd_buffer.c b/src/amd/vulkan/radv_cmd_buffer.c
index 9da42fe03e..5dbdb3d996 100644
--- a/src/amd/vulkan/radv_cmd_buffer.c
+++ b/src/amd/vulkan/radv_cmd_buffer.c
@@ -2596,6 +2596,11 @@ VkResult radv_EndCommandBuffer(
 		si_emit_cache_flush(cmd_buffer);
 	}
 
+	/* Make sure CP DMA is idle at the end of IBs because the kernel
+	 * doesn't wait for it.
+	 */
+	si_cp_dma_wait_for_idle(cmd_buffer);
+
 	vk_free(&cmd_buffer->pool->alloc, cmd_buffer->state.attachments);
 
 	if (!cmd_buffer->device->ws->cs_finalize(cmd_buffer->cs))
@@ -4242,6 +4247,11 @@ radv_barrier(struct radv_cmd_buffer *cmd_buffer,
 					     0);
 	}
 
+	/* Make sure CP DMA is idle because the driver might have performed a
+	 * DMA operation for copying or filling buffers/images.
+	 */
+	si_cp_dma_wait_for_idle(cmd_buffer);
+
 	cmd_buffer->state.flush_bits |= dst_flush_bits;
 }
 
@@ -4292,6 +4302,11 @@ static void write_event(struct radv_cmd_buffer *cmd_buffer,
 		VK_PIPELINE_STAGE_DRAW_INDIRECT_BIT |
 		VK_PIPELINE_STAGE_VERTEX_INPUT_BIT;
 
+	/* Make sure CP DMA is idle because the driver might have performed a
+	 * DMA operation for copying or filling buffers/images.
+	 */
+	si_cp_dma_wait_for_idle(cmd_buffer);
+
 	/* TODO: Emit EOS events for syncing PS/CS stages. */
 
 	if (!(stageMask & ~top_of_pipe_flags)) {
diff --git a/src/amd/vulkan/radv_private.h b/src/amd/vulkan/radv_private.h
index 4e4b3a6037..2400de49a2 100644
--- a/src/amd/vulkan/radv_private.h
+++ b/src/amd/vulkan/radv_private.h
@@ -979,6 +979,9 @@ struct radv_cmd_state {
 	uint32_t last_num_instances;
 	uint32_t last_first_instance;
 	uint32_t last_vertex_offset;
+
+	/* Whether CP DMA is busy/idle. */
+	bool dma_is_busy;
 };
 
 struct radv_cmd_pool {
@@ -1091,6 +1094,8 @@ void si_cp_dma_prefetch(struct radv_cmd_buffer *cmd_buffer, uint64_t va,
                         unsigned size);
 void si_cp_dma_clear_buffer(struct radv_cmd_buffer *cmd_buffer, uint64_t va,
 			    uint64_t size, unsigned value);
+void si_cp_dma_wait_for_idle(struct radv_cmd_buffer *cmd_buffer);
+
 void radv_set_db_count_control(struct radv_cmd_buffer *cmd_buffer);
 bool
 radv_cmd_buffer_upload_alloc(struct radv_cmd_buffer *cmd_buffer,
diff --git a/src/amd/vulkan/si_cmd_buffer.c b/src/amd/vulkan/si_cmd_buffer.c
index 454fd8c39c..6d566a918d 100644
--- a/src/amd/vulkan/si_cmd_buffer.c
+++ b/src/amd/vulkan/si_cmd_buffer.c
@@ -1040,7 +1040,6 @@ static void si_emit_cp_dma(struct radv_cmd_buffer *cmd_buffer,
 	struct radeon_cmdbuf *cs = cmd_buffer->cs;
 	uint32_t header = 0, command = 0;
 
-	assert(size);
 	assert(size <= cp_dma_max_byte_count(cmd_buffer));
 
 	radeon_check_space(cmd_buffer->device->ws, cmd_buffer->cs, 9);
@@ -1099,9 +1098,14 @@ static void si_emit_cp_dma(struct radv_cmd_buffer *cmd_buffer,
 	 * indices. If we wanted to execute CP DMA in PFP, this packet
 	 * should precede it.
 	 */
-	if ((flags & CP_DMA_SYNC) && cmd_buffer->queue_family_index == RADV_QUEUE_GENERAL) {
-		radeon_emit(cs, PKT3(PKT3_PFP_SYNC_ME, 0, cmd_buffer->state.predicating));
-		radeon_emit(cs, 0);
+	if (flags & CP_DMA_SYNC) {
+		if (cmd_buffer->queue_family_index == RADV_QUEUE_GENERAL) {
+			radeon_emit(cs, PKT3(PKT3_PFP_SYNC_ME, 0, cmd_buffer->state.predicating));
+			radeon_emit(cs, 0);
+		}
+
+		/* CP will see the sync flag and wait for all DMAs to complete. */
+		cmd_buffer->state.dma_is_busy = false;
 	}
 
 	if (unlikely(cmd_buffer->device->trace_bo))
@@ -1165,6 +1169,8 @@ void si_cp_dma_buffer_copy(struct radv_cmd_buffer *cmd_buffer,
 	uint64_t main_src_va, main_dest_va;
 	uint64_t skipped_size = 0, realign_size = 0;
 
+	/* Assume that we are not going to sync after the last DMA operation. */
+	cmd_buffer->state.dma_is_busy = true;
 
 	if (cmd_buffer->device->physical_device->rad_info.family <= CHIP_CARRIZO ||
 	    cmd_buffer->device->physical_device->rad_info.family == CHIP_STONEY) {
@@ -1228,6 +1234,9 @@ void si_cp_dma_clear_buffer(struct radv_cmd_buffer *cmd_buffer, uint64_t va,
 
 	assert(va % 4 == 0 && size % 4 == 0);
 
+	/* Assume that we are not going to sync after the last DMA operation. */
+	cmd_buffer->state.dma_is_busy = true;
+
 	while (size) {
 		unsigned byte_count = MIN2(size, cp_dma_max_byte_count(cmd_buffer));
 		unsigned dma_flags = CP_DMA_CLEAR;
@@ -1243,6 +1252,25 @@ void si_cp_dma_clear_buffer(struct radv_cmd_buffer *cmd_buffer, uint64_t va,
 	}
 }
 
+void si_cp_dma_wait_for_idle(struct radv_cmd_buffer *cmd_buffer)
+{
+	if (cmd_buffer->device->physical_device->rad_info.chip_class < CIK)
+		return;
+
+	if (!cmd_buffer->state.dma_is_busy)
+		return;
+
+	/* Issue a dummy DMA that copies zero bytes.
+	 *
+	 * The DMA engine will see that there's no work to do and skip this
+	 * DMA request, however, the CP will see the sync flag and still wait
+	 * for all DMAs to complete.
+	 */
+	si_emit_cp_dma(cmd_buffer, 0, 0, 0, CP_DMA_SYNC);
+
+	cmd_buffer->state.dma_is_busy = false;
+}
+
 /* For MSAA sample positions. */
 #define FILL_SREG(s0x, s0y, s1x, s1y, s2x, s2y, s3x, s3y)  \
 	(((s0x) & 0xf) | (((unsigned)(s0y) & 0xf) << 4) |		   \
-- 
2.18.0