Revert "drm/msm/dpu: Enable quad-pipe for DSC and dual-DSI case"

This reverts commit d7ec9366b1.

The dual-DSI dual-DSC scenario seems to be broken by this commit.

Reported-by: Marijn Suijten <marijn.suijten@somainline.org>
Closes: https://lore.kernel.org/r/aUR2b3FOSisTfDFj@SoMainline.org
Signed-off-by: Abel Vesa <abel.vesa@oss.qualcomm.com>
Fixes: d7ec9366b1 ("drm/msm/dpu: Enable quad-pipe for DSC and dual-DSI case")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/695550/
Link: https://lore.kernel.org/r/20251219-drm-msm-dpu-revert-quad-pipe-broken-v1-2-654b46505f84@oss.qualcomm.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c

@@ -200,7 +200,7 @@ static int dpu_crtc_get_lm_crc(struct drm_crtc *crtc,
 		struct dpu_crtc_state *crtc_state)
 {
 	struct dpu_crtc_mixer *m;
-	u32 crcs[CRTC_QUAD_MIXERS];
+	u32 crcs[CRTC_DUAL_MIXERS];
 
 	int rc = 0;
 	int i;
@@ -1328,7 +1328,6 @@ static struct msm_display_topology dpu_crtc_get_topology(
 	struct drm_display_mode *mode = &crtc_state->adjusted_mode;
 	struct msm_display_topology topology = {0};
 	struct drm_encoder *drm_enc;
-	u32 num_rt_intf;
 
 	drm_for_each_encoder_mask(drm_enc, crtc->dev, crtc_state->encoder_mask)
 		dpu_encoder_update_topology(drm_enc, &topology, crtc_state->state,
@@ -1342,14 +1341,11 @@ static struct msm_display_topology dpu_crtc_get_topology(
 	 * Dual display
 	 * 2 LM, 2 INTF ( Split display using 2 interfaces)
 	 *
-	 * If DSC is enabled, try to use 4:4:2 topology if there is enough
-	 * resource. Otherwise, use 2:2:2 topology.
-	 *
 	 * Single display
 	 * 1 LM, 1 INTF
 	 * 2 LM, 1 INTF (stream merge to support high resolution interfaces)
 	 *
-	 * If DSC is enabled, use 2:2:1 topology
+	 * If DSC is enabled, use 2 LMs for 2:2:1 topology
 	 *
 	 * Add dspps to the reservation requirements if ctm is requested
 	 *
@@ -1361,23 +1357,14 @@ static struct msm_display_topology dpu_crtc_get_topology(
 	 * (mode->hdisplay > MAX_HDISPLAY_SPLIT) check.
 	 */
 
-	num_rt_intf = topology.num_intf;
-	if (topology.cwb_enabled)
-		num_rt_intf--;
-
-	if (topology.num_dsc) {
-		if (dpu_kms->catalog->dsc_count >= num_rt_intf * 2)
-			topology.num_dsc = num_rt_intf * 2;
-		else
-			topology.num_dsc = num_rt_intf;
-		topology.num_lm = topology.num_dsc;
-	} else if (num_rt_intf == 2) {
+	if (topology.num_intf == 2 && !topology.cwb_enabled)
 		topology.num_lm = 2;
-	} else if (dpu_kms->catalog->caps->has_3d_merge) {
+	else if (topology.num_dsc == 2)
+		topology.num_lm = 2;
+	else if (dpu_kms->catalog->caps->has_3d_merge)
 		topology.num_lm = (mode->hdisplay > MAX_HDISPLAY_SPLIT) ? 2 : 1;
-	} else {
+	else
 		topology.num_lm = 1;
-	}
 
 	if (crtc_state->ctm)
 		topology.num_dspp = topology.num_lm;

drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h

@@ -210,7 +210,7 @@ struct dpu_crtc_state {
 
 	bool bw_control;
 	bool bw_split_vote;
-	struct drm_rect lm_bounds[CRTC_QUAD_MIXERS];
+	struct drm_rect lm_bounds[CRTC_DUAL_MIXERS];
 
 	uint64_t input_fence_timeout_ns;
 
@@ -218,10 +218,10 @@ struct dpu_crtc_state {
 
 	/* HW Resources reserved for the crtc */
 	u32 num_mixers;
-	struct dpu_crtc_mixer mixers[CRTC_QUAD_MIXERS];
+	struct dpu_crtc_mixer mixers[CRTC_DUAL_MIXERS];
 
 	u32 num_ctls;
-	struct dpu_hw_ctl *hw_ctls[CRTC_QUAD_MIXERS];
+	struct dpu_hw_ctl *hw_ctls[CRTC_DUAL_MIXERS];
 
 	enum dpu_crtc_crc_source crc_source;
 	int crc_frame_skip_count;

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c

@@ -55,7 +55,7 @@
 #define MAX_PHYS_ENCODERS_PER_VIRTUAL \
 	(MAX_H_TILES_PER_DISPLAY * NUM_PHYS_ENCODER_TYPES)
 
-#define MAX_CHANNELS_PER_ENC 4
+#define MAX_CHANNELS_PER_ENC 2
 #define MAX_CWB_PER_ENC 2
 
 #define IDLE_SHORT_TIMEOUT	1
@@ -661,6 +661,7 @@ void dpu_encoder_update_topology(struct drm_encoder *drm_enc,
 	struct dpu_encoder_virt *dpu_enc = to_dpu_encoder_virt(drm_enc);
 	struct msm_drm_private *priv = dpu_enc->base.dev->dev_private;
 	struct msm_display_info *disp_info = &dpu_enc->disp_info;
+	struct dpu_kms *dpu_kms = to_dpu_kms(priv->kms);
 	struct drm_connector *connector;
 	struct drm_connector_state *conn_state;
 	struct drm_framebuffer *fb;
@@ -674,12 +675,22 @@ void dpu_encoder_update_topology(struct drm_encoder *drm_enc,
 
 	dsc = dpu_encoder_get_dsc_config(drm_enc);
 
-	/*
-	 * Set DSC number as 1 to mark the enabled status, will be adjusted
-	 * in dpu_crtc_get_topology()
-	 */
-	if (dsc)
-		topology->num_dsc = 1;
+	/* We only support 2 DSC mode (with 2 LM and 1 INTF) */
+	if (dsc) {
+		/*
+		 * Use 2 DSC encoders, 2 layer mixers and 1 or 2 interfaces
+		 * when Display Stream Compression (DSC) is enabled,
+		 * and when enough DSC blocks are available.
+		 * This is power-optimal and can drive up to (including) 4k
+		 * screens.
+		 */
+		WARN(topology->num_intf > 2,
+		     "DSC topology cannot support more than 2 interfaces\n");
+		if (topology->num_intf >= 2 || dpu_kms->catalog->dsc_count >= 2)
+			topology->num_dsc = 2;
+		else
+			topology->num_dsc = 1;
+	}
 
 	connector = drm_atomic_get_new_connector_for_encoder(state, drm_enc);
 	if (!connector)
@@ -2169,8 +2180,8 @@ static void dpu_encoder_helper_reset_mixers(struct dpu_encoder_phys *phys_enc)
 {
 	int i, num_lm;
 	struct dpu_global_state *global_state;
-	struct dpu_hw_blk *hw_lm[MAX_CHANNELS_PER_ENC];
-	struct dpu_hw_mixer *hw_mixer[MAX_CHANNELS_PER_ENC];
+	struct dpu_hw_blk *hw_lm[2];
+	struct dpu_hw_mixer *hw_mixer[2];
 	struct dpu_hw_ctl *ctl = phys_enc->hw_ctl;
 
 	/* reset all mixers for this encoder */

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h

@@ -302,7 +302,7 @@ static inline enum dpu_3d_blend_mode dpu_encoder_helper_get_3d_blend_mode(
 
 	/* Use merge_3d unless DSC MERGE topology is used */
 	if (phys_enc->split_role == ENC_ROLE_SOLO &&
-	    (dpu_cstate->num_mixers != 1) &&
+	    dpu_cstate->num_mixers == CRTC_DUAL_MIXERS &&
 	    !dpu_encoder_use_dsc_merge(phys_enc->parent))
 		return BLEND_3D_H_ROW_INT;
 

drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h

@@ -24,7 +24,7 @@
 #define DPU_MAX_IMG_WIDTH 0x3fff
 #define DPU_MAX_IMG_HEIGHT 0x3fff
 
-#define CRTC_QUAD_MIXERS	4
+#define CRTC_DUAL_MIXERS	2
 
 #define MAX_XIN_COUNT 16
 

drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h

@@ -34,7 +34,7 @@
 #define DPU_MAX_PLANES			4
 #endif
 
-#define STAGES_PER_PLANE		2
+#define STAGES_PER_PLANE		1
 #define PIPES_PER_STAGE			2
 #define PIPES_PER_PLANE			(PIPES_PER_STAGE * STAGES_PER_PLANE)
 #ifndef DPU_MAX_DE_CURVES