drm/nouveau/disp/gm200-: enforce identity-mapped SOR assignment for LVDS/eDP panels

Fixes eDP backlight issues on more recent laptops.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvkm/engine/disp/base.c

@@ -275,6 +275,7 @@ nvkm_disp_oneinit(struct nvkm_engine *engine)
 	struct nvkm_outp *outp, *outt, *pair;
 	struct nvkm_conn *conn;
 	struct nvkm_head *head;
+	struct nvkm_ior *ior;
 	struct nvbios_connE connE;
 	struct dcb_output dcbE;
 	u8  hpd = 0, ver, hdr;
@@ -399,6 +400,19 @@ nvkm_disp_oneinit(struct nvkm_engine *engine)
 			return ret;
 	}
 
+	/* Enforce identity-mapped SOR assignment for panels, which have
+	 * certain bits (ie. backlight controls) wired to a specific SOR.
+	 */
+	list_for_each_entry(outp, &disp->outp, head) {
+		if (outp->conn->info.type == DCB_CONNECTOR_LVDS ||
+		    outp->conn->info.type == DCB_CONNECTOR_eDP) {
+			ior = nvkm_ior_find(disp, SOR, ffs(outp->info.or) - 1);
+			if (!WARN_ON(!ior))
+				ior->identity = true;
+			outp->identity = true;
+		}
+	}
+
 	i = 0;
 	list_for_each_entry(head, &disp->head, head)
 		i = max(i, head->id + 1);

drivers/gpu/drm/nouveau/nvkm/engine/disp/ior.h

@@ -16,6 +16,7 @@ struct nvkm_ior {
 	char name[8];
 
 	struct list_head head;
+	bool identity;
 
 	struct nvkm_ior_state {
 		struct nvkm_outp *outp;

drivers/gpu/drm/nouveau/nvkm/engine/disp/outp.c

@@ -129,17 +129,26 @@ nvkm_outp_acquire(struct nvkm_outp *outp, u8 user)
 	if (proto == UNKNOWN)
 		return -ENOSYS;
 
+	/* Deal with panels requiring identity-mapped SOR assignment. */
+	if (outp->identity) {
+		ior = nvkm_ior_find(outp->disp, SOR, ffs(outp->info.or) - 1);
+		if (WARN_ON(!ior))
+			return -ENOSPC;
+		return nvkm_outp_acquire_ior(outp, user, ior);
+	}
+
 	/* First preference is to reuse the OR that is currently armed
 	 * on HW, if any, in order to prevent unnecessary switching.
 	 */
 	list_for_each_entry(ior, &outp->disp->ior, head) {
-		if (!ior->asy.outp && ior->arm.outp == outp)
+		if (!ior->identity && !ior->asy.outp && ior->arm.outp == outp)
 			return nvkm_outp_acquire_ior(outp, user, ior);
 	}
 
 	/* Failing that, a completely unused OR is the next best thing. */
 	list_for_each_entry(ior, &outp->disp->ior, head) {
-		if (!ior->asy.outp && ior->type == type && !ior->arm.outp &&
+		if (!ior->identity &&
+		    !ior->asy.outp && ior->type == type && !ior->arm.outp &&
 		    (ior->func->route.set || ior->id == __ffs(outp->info.or)))
 			return nvkm_outp_acquire_ior(outp, user, ior);
 	}
@@ -148,7 +157,7 @@ nvkm_outp_acquire(struct nvkm_outp *outp, u8 user)
 	 * but will be released during the next modeset.
 	 */
 	list_for_each_entry(ior, &outp->disp->ior, head) {
-		if (!ior->asy.outp && ior->type == type &&
+		if (!ior->identity && !ior->asy.outp && ior->type == type &&
 		    (ior->func->route.set || ior->id == __ffs(outp->info.or)))
 			return nvkm_outp_acquire_ior(outp, user, ior);
 	}

drivers/gpu/drm/nouveau/nvkm/engine/disp/outp.h

@@ -16,6 +16,7 @@ struct nvkm_outp {
 
 	struct list_head head;
 	struct nvkm_conn *conn;
+	bool identity;
 
 	/* Assembly state. */
 #define NVKM_OUTP_PRIV 1