drm/msm/dpu: Add CWB to msm_display_topology

Currently, the topology is calculated based on the assumption that the
user cannot request real-time and writeback simultaneously. For example,
the number of LMs and CTLs are currently based off the number of phys
encoders under the assumption there will be at least 1 LM/CTL per phys
encoder.

This will not hold true for concurrent writeback as both phys encoders
(1 real-time and 1 writeback) must be driven by 1 LM/CTL when concurrent
writeback is enabled.

To account for this, add a cwb_enabled flag and only adjust the number of
CTL/LMs needed by a given topology based on the number of phys encoders
only if CWB is not enabled.

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/637486/
Link: https://lore.kernel.org/r/20250214-concurrent-wb-v6-4-a44c293cf422@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

3 files changed, 24 insertions, 3 deletions

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index 10653bd52885..27078d3f90b4 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -1246,6 +1246,8 @@ static struct msm_display_topology dpu_crtc_get_topology(
 		dpu_encoder_update_topology(drm_enc, &topology, crtc_state->state,
 					    &crtc_state->adjusted_mode);
 
+	topology.cwb_enabled = drm_crtc_in_clone_mode(crtc_state);
+
 	/*
 	 * Datapath topology selection
 	 *
@@ -1259,9 +1261,16 @@ static struct msm_display_topology dpu_crtc_get_topology(
 	 * If DSC is enabled, use 2 LMs for 2:2:1 topology
 	 *
 	 * Add dspps to the reservation requirements if ctm is requested
+	 *
+	 * Only hardcode num_lm to 2 for cases where num_intf == 2 and CWB is not
+	 * enabled. This is because in cases where CWB is enabled, num_intf will
+	 * count both the WB and real-time phys encoders.
+	 *
+	 * For non-DSC CWB usecases, have the num_lm be decided by the
+	 * (mode->hdisplay > MAX_HDISPLAY_SPLIT) check.
 	 */
 
-	if (topology.num_intf == 2)
+	if (topology.num_intf == 2 && !topology.cwb_enabled)
 		topology.num_lm = 2;
 	else if (topology.num_dsc == 2)
 		topology.num_lm = 2;
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
index a7b4086ae990..0fbb92021b18 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
@@ -381,8 +381,18 @@ static int _dpu_rm_reserve_ctls(
 	int i = 0, j, num_ctls;
 	bool needs_split_display;
 
-	/* each hw_intf needs its own hw_ctrl to program its control path */
-	num_ctls = top->num_intf;
+	/*
+	 * For non-CWB mode, each hw_intf needs its own hw_ctl to program its
+	 * control path.
+	 *
+	 * Hardcode num_ctls to 1 if CWB is enabled because in CWB, both the
+	 * writeback and real-time encoders must be driven by the same control
+	 * path
+	 */
+	if (top->cwb_enabled)
+		num_ctls = 1;
+	else
+		num_ctls = top->num_intf;
 
 	needs_split_display = _dpu_rm_needs_split_display(top);
 
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
index 463c532cdfdf..b854e42d319d 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
@@ -52,6 +52,7 @@ struct dpu_rm_sspp_requirements {
  * @num_dspp:     number of dspp blocks used
  * @num_dsc:      number of Display Stream Compression (DSC) blocks used
  * @needs_cdm:    indicates whether cdm block is needed for this display topology
+ * @cwb_enabled:  indicates whether CWB is enabled for this display topology
  */
 struct msm_display_topology {
 	u32 num_lm;
@@ -59,6 +60,7 @@ struct msm_display_topology {
 	u32 num_dspp;
 	u32 num_dsc;
 	bool needs_cdm;
+	bool cwb_enabled;
 };
 
 int dpu_rm_init(struct drm_device *dev,