[Nouveau] [PATCH 1/1] drm/nouveau/disp: prefer identity-mapped route of SOR <-> macro link

[Danilo Krummrich]

With DCB 4.1 implemented by VBIOS since GM20x GPUs, SOR crossbar
routing should be possible, such that any SOR sublink can drive
any macro link. Therefore, if crossbar routing is available,
the first suitable SOR was picked.

Unfortunately, there's at least one card where some SORs being
being connected to a particular macro link not matching the identity
of each other are causing failures.

To fix this, when searching for a suitable SOR to be mapped to a
macro link prefer a SOR which maps the identity of the macro link.

Signed-off-by: Danilo Krummrich <danilokrummrich at dk-develop.de>
---
 drivers/gpu/drm/nouveau/nvkm/engine/disp/outp.c | 38 +++++++++++++++++--------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/outp.c b/drivers/gpu/drm/nouveau/nvkm/engine/disp/outp.c
index be9e7f8c3b23..b7af9349504e 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/disp/outp.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/disp/outp.c
@@ -112,7 +112,7 @@ nvkm_outp_acquire_ior(struct nvkm_outp *outp, u8 user, struct nvkm_ior *ior)
 int
 nvkm_outp_acquire(struct nvkm_outp *outp, u8 user)
 {
-	struct nvkm_ior *ior = outp->ior;
+	struct nvkm_ior *_ior, *ior = outp->ior;
 	enum nvkm_ior_proto proto;
 	enum nvkm_ior_type type;
 
@@ -130,26 +130,40 @@ nvkm_outp_acquire(struct nvkm_outp *outp, u8 user)
 	/* 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)
-			return nvkm_outp_acquire_ior(outp, user, ior);
+	list_for_each_entry(_ior, &outp->disp->ior, head) {
+		if (!_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 &&
-		    (ior->func->route.set || ior->id == __ffs(outp->info.or)))
-			return nvkm_outp_acquire_ior(outp, user, ior);
+	ior = NULL;
+	list_for_each_entry(_ior, &outp->disp->ior, head) {
+		if (!_ior->asy.outp && _ior->type == type && !_ior->arm.outp) {
+			/* Prefer identity-mapped route. */
+			if (_ior->id == __ffs(outp->info.or))
+				return nvkm_outp_acquire_ior(outp, user, _ior);
+			else if (!ior)
+				ior = _ior;
+		}
 	}
+	if (ior && ior->func->route.set)
+		return nvkm_outp_acquire_ior(outp, user, ior);
 
 	/* Last resort is to assign an OR that's already active on HW,
 	 * but will be released during the next modeset.
 	 */
-	list_for_each_entry(ior, &outp->disp->ior, head) {
-		if (!ior->asy.outp && ior->type == type &&
-		    (ior->func->route.set || ior->id == __ffs(outp->info.or)))
-			return nvkm_outp_acquire_ior(outp, user, ior);
+	ior = NULL;
+	list_for_each_entry(_ior, &outp->disp->ior, head) {
+		if (!_ior->asy.outp && _ior->type == type) {
+			/* Again prefer identity-mapped route. */
+			if (_ior->id == __ffs(outp->info.or))
+				return nvkm_outp_acquire_ior(outp, user, _ior);
+			else if (!ior)
+				ior = _ior;
+		}
 	}
+	if (ior && ior->func->route.set)
+		return nvkm_outp_acquire_ior(outp, user, _ior);
 
 	return -ENOSPC;
 }
-- 
2.14.1