drm/apple: 5K@120/180 on J514S by splitting the display across both external pipes (opt-in)

drivers/gpu/drm/apple/dcp-fabric.c

@@ -34,6 +34,11 @@ module_param(tiled_split, bool, 0644);
 MODULE_PARM_DESC(tiled_split,
 		 "Drive both halves of a tiled Thunderbolt display (LG UltraFine 5K) on one pipeline, through its two DPTX ports (default: on)");
 
+static bool split_dock_main;
+module_param(split_dock_main, bool, 0644);
+MODULE_PARM_DESC(split_dock_main,
+		 "EXPERIMENT: put a Thunderbolt display on the free HDMI pipeline (dcpext0), so split_modeset can drive it over two pipes as macOS does");
+
 static bool typec_follow_crtc = true;
 module_param(typec_follow_crtc, bool, 0444);
 MODULE_PARM_DESC(typec_follow_crtc,
@@ -180,7 +185,9 @@ static bool dcp_typec_route_busy(struct apple_dcp_typec_route *route)
 	struct apple_dcp *dcp = route->dcp;
 
 	return dcp_typec_route_fixed_output_busy(route) ||
-	       (dcp->external_native && iomfb_v14_7_external_failed(dcp));
+	       (dcp->external_native && iomfb_v14_7_external_failed(dcp)) ||
+	       /* Experimental (split_modeset): lent to another display's split. */
+	       (dcp->external_native && iomfb_v14_7_split_helper(dcp));
 }
 
 static bool dcp_typec_route_available(struct apple_dcp_typec_route *route)
@@ -1954,6 +1961,47 @@ static int dcp_tb_candidate(void *data)
 			return ret;
 	}
 
+	/*
+	 * Experimental (split_dock_main): a display driven over two pipes
+	 * needs the HDMI pipeline (the hybrid, dcpext0 on T6030) as the one
+	 * that owns the link, as macOS does. Take it for the tunnel while it is
+	 * free and no HDMI display is present.
+	 */
+	if (READ_ONCE(split_dock_main) && !best->dcp->fixed_phy) {
+		struct apple_dcp_typec_route *r;
+
+		list_for_each_entry(r, &port->routes, port_link) {
+			struct apple_dcp *h = r->dcp;
+			bool hdmi_empty;
+
+			if (r == best || !h->fixed_phy || !dcp_typec_tunnel_ctl(r, dpin))
+				continue;
+			/*
+			 * HDMI presence stays SETTLING for DCP_HDMI_HOLD_MS after
+			 * any edge, including the first sample at boot, which is
+			 * when a dock's tunnel comes up. Read the HPD line then.
+			 */
+			switch (dcp_hdmi_presence(h)) {
+			case DCP_FABRIC_ABSENT:
+				hdmi_empty = true;
+				break;
+			case DCP_FABRIC_SETTLING:
+				hdmi_empty = h->hdmi_hpd && !gpiod_get_value_cansleep(h->hdmi_hpd);
+				break;
+			default:
+				hdmi_empty = false;
+				break;
+			}
+			if (!hdmi_empty || h->active_typec_route || dcp_typec_safe_held(h) ||
+			    dcp_typec_route_busy(r))
+				continue;
+			dev_info(r->dcp->dev, "split_dock_main: tunnel dpin%u takes this pipeline instead of %s\n",
+				 dpin, dev_name(best->dcp->dev));
+			best = r;
+			break;
+		}
+	}
+
 	ctl = dcp_typec_tunnel_ctl(best, dpin);
 	if (!ctl)
 		return -EOPNOTSUPP;

drivers/gpu/drm/apple/dptxep.c

@@ -99,6 +99,21 @@ struct dptxport_apcall_set_tiled {
 #define DPTX_TILE_HINT_HEIGHT	0x3c
 #define DPTX_TILE_HINT_MIN_SIZE	0x40
 
+/*
+ * Experimental (split_alloc): macOS 14 on J514S answers this call
+ * with a pipe allocation at +0x64..+0x77 (seen in a hypervisor trace:
+ * 1, 1, 6144, 1438000000, 1274019840). The DCP then offers 5K@120/180 as
+ * split timings (ID + 10000). Off by default; can be flipped at runtime and
+ * takes effect on the next hotplug.
+ */
+static bool split_alloc;
+module_param(split_alloc, bool, 0644);
+MODULE_PARM_DESC(split_alloc,
+		 "EXPERIMENT: offer a dcpext peer pipe in SetTiledDisplayHints replies like macOS 14");
+
+#define DPTX_SPLIT_ALLOC_OFF	0x64
+#define DPTX_SPLIT_ALLOC_END	0x78
+
 /*
  * A Thunderbolt DP tunnel uses the same CORE|ATC|DIE|CONNECTED target as a
  * direct alt-mode PHY: CORE is the DFP port (0 = dpphy, 1/2 = dpin0/dpin1)
@@ -661,6 +676,30 @@ static int dptxport_call_set_tiled_display_hint(struct apple_epic_service *servi
 	}
 
 	reply->retcode = cpu_to_le32(1);
+
+	/* Only for a single-stream sink that reports its size (not a 2-tile LG). */
+	if (READ_ONCE(split_alloc) && data_size >= DPTX_SPLIT_ALLOC_END &&
+	    reply_size >= DPTX_SPLIT_ALLOC_END &&
+	    get_unaligned_le32(hint + DPTX_TILE_HINT_TILES_H) <= 1 &&
+	    get_unaligned_le32(hint + DPTX_TILE_HINT_WIDTH) &&
+	    get_unaligned_le32(hint + DPTX_TILE_HINT_HEIGHT)) {
+		u8 *r = reply_;
+
+		put_unaligned_le32(1, r + DPTX_SPLIT_ALLOC_OFF + 0x00);
+		put_unaligned_le32(1, r + DPTX_SPLIT_ALLOC_OFF + 0x04);
+		put_unaligned_le32(0x1800, r + DPTX_SPLIT_ALLOC_OFF + 0x08);
+		put_unaligned_le32(0x55b62380, r + DPTX_SPLIT_ALLOC_OFF + 0x0c);
+		put_unaligned_le32(0x4bf00000, r + DPTX_SPLIT_ALLOC_OFF + 0x10);
+		dev_info(service->ep->dcp->dev,
+			 "DPTXPort: EXPERIMENT split_alloc: offered a peer pipe for %ux%u (data %zu, reply %zu)\n",
+			 get_unaligned_le32(hint + DPTX_TILE_HINT_WIDTH),
+			 get_unaligned_le32(hint + DPTX_TILE_HINT_HEIGHT),
+			 data_size, reply_size);
+	} else if (READ_ONCE(split_alloc)) {
+		dev_info(service->ep->dcp->dev,
+			 "DPTXPort: EXPERIMENT split_alloc: hint not used (data %zu, reply %zu)\n",
+			 data_size, reply_size);
+	}
 	return 0;
 }