drm/amd/display: Remove wait while locked

[Why]
We wait for mpc idle while in a locked state, leading to potential
deadlock.

[What]
Move the wait_for_idle call to outside of HW lock. This and a
call to wait_drr_doublebuffer_pending_clear are moved added to a new
static helper function called wait_for_outstanding_hw_updates, to make
the interface clearer.

Cc: [email protected]
Fixes: 8f0d304 ("drm/amd/display: Do not commit pipe when updating DRR")
Reviewed-by: Jun Lei <[email protected]>
Acked-by: Hamza Mahfooz <[email protected]>
Signed-off-by: Gabe Teeger <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: Gabe Teeger

drivers/gpu/drm/amd/display/dc/Makefile

@@ -78,3 +78,4 @@ DC_EDID += dc_edid_parser.o
 AMD_DISPLAY_DMUB = $(addprefix $(AMDDALPATH)/dc/,$(DC_DMUB))
 AMD_DISPLAY_EDID = $(addprefix $(AMDDALPATH)/dc/,$(DC_EDID))
 AMD_DISPLAY_FILES += $(AMD_DISPLAY_DMUB) $(AMD_DISPLAY_EDID)
+

drivers/gpu/drm/amd/display/dc/core/dc.c

@@ -3501,6 +3501,45 @@ static void commit_planes_for_stream_fast(struct dc *dc,
 		top_pipe_to_program->stream->update_flags.raw = 0;
 }
 
+static void wait_for_outstanding_hw_updates(struct dc *dc, const struct dc_state *dc_context)
+{
+/*
+ * This function calls HWSS to wait for any potentially double buffered
+ * operations to complete. It should be invoked as a pre-amble prior
+ * to full update programming before asserting any HW locks.
+ */
+	int pipe_idx;
+	int opp_inst;
+	int opp_count = dc->res_pool->pipe_count;
+	struct hubp *hubp;
+	int mpcc_inst;
+	const struct pipe_ctx *pipe_ctx;
+
+	for (pipe_idx = 0; pipe_idx < dc->res_pool->pipe_count; pipe_idx++) {
+		pipe_ctx = &dc_context->res_ctx.pipe_ctx[pipe_idx];
+
+		if (!pipe_ctx->stream)
+			continue;
+
+		if (pipe_ctx->stream_res.tg->funcs->wait_drr_doublebuffer_pending_clear)
+			pipe_ctx->stream_res.tg->funcs->wait_drr_doublebuffer_pending_clear(pipe_ctx->stream_res.tg);
+
+		hubp = pipe_ctx->plane_res.hubp;
+		if (!hubp)
+			continue;
+
+		mpcc_inst = hubp->inst;
+		// MPCC inst is equal to pipe index in practice
+		for (opp_inst = 0; opp_inst < opp_count; opp_inst++) {
+			if (dc->res_pool->opps[opp_inst]->mpcc_disconnect_pending[mpcc_inst]) {
+				dc->res_pool->mpc->funcs->wait_for_idle(dc->res_pool->mpc, mpcc_inst);
+				dc->res_pool->opps[opp_inst]->mpcc_disconnect_pending[mpcc_inst] = false;
+				break;
+			}
+		}
+	}
+}
+
 static void commit_planes_for_stream(struct dc *dc,
 		struct dc_surface_update *srf_updates,
 		int surface_count,
@@ -3519,24 +3558,9 @@ static void commit_planes_for_stream(struct dc *dc,
 	// dc->current_state anymore, so we have to cache it before we apply
 	// the new SubVP context
 	subvp_prev_use = false;
-
-
 	dc_z10_restore(dc);
-
-	if (update_type == UPDATE_TYPE_FULL) {
-		/* wait for all double-buffer activity to clear on all pipes */
-		int pipe_idx;
-
-		for (pipe_idx = 0; pipe_idx < dc->res_pool->pipe_count; pipe_idx++) {
-			struct pipe_ctx *pipe_ctx = &context->res_ctx.pipe_ctx[pipe_idx];
-
-			if (!pipe_ctx->stream)
-				continue;
-
-			if (pipe_ctx->stream_res.tg->funcs->wait_drr_doublebuffer_pending_clear)
-				pipe_ctx->stream_res.tg->funcs->wait_drr_doublebuffer_pending_clear(pipe_ctx->stream_res.tg);
-		}
-	}
+	if (update_type == UPDATE_TYPE_FULL)
+		wait_for_outstanding_hw_updates(dc, context);
 
 	if (update_type == UPDATE_TYPE_FULL) {
 		dc_allow_idle_optimizations(dc, false);

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c

@@ -1561,17 +1561,6 @@ static void dcn20_update_dchubp_dpp(
 			|| plane_state->update_flags.bits.global_alpha_change
 			|| plane_state->update_flags.bits.per_pixel_alpha_change) {
 		// MPCC inst is equal to pipe index in practice
-		int mpcc_inst = hubp->inst;
-		int opp_inst;
-		int opp_count = dc->res_pool->pipe_count;
-
-		for (opp_inst = 0; opp_inst < opp_count; opp_inst++) {
-			if (dc->res_pool->opps[opp_inst]->mpcc_disconnect_pending[mpcc_inst]) {
-				dc->res_pool->mpc->funcs->wait_for_idle(dc->res_pool->mpc, mpcc_inst);
-				dc->res_pool->opps[opp_inst]->mpcc_disconnect_pending[mpcc_inst] = false;
-				break;
-			}
-		}
 		hws->funcs.update_mpcc(dc, pipe_ctx);
 	}