[PATCH] Fix broken initialization when SCDC is supported but not implemented

[Giuseppe Ranieri <giuseppe@ranieri.dev>]

This patch fix the missing scdc implementation on scdc enabled card behaviour init call and add debug message on error:

 - FIX: when the scdc implementation is missing the call of nvkm_uoutp_mthd_hdmi don't return anymore an error code but emit a OUTP_DBG log message and continue the initialization process

 - ADD: an NV_ERROR message where  error code is return by the nvif_outp_hdmi call in nv50_hdmi_enable method

Solve problem with (scdc enabled) card that don´t had scdc implementation in nouveau driver.

Signed-off-by: Giuseppe Ranieri <giuseppe@ranieri.dev>
---

diff '--color=auto' -ur a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c	2025-11-30 23:42:10.000000000 +0100
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c	2026-01-17 01:27:34.150245394 +0100
@@ -819,9 +819,11 @@
 	ret = nvif_outp_hdmi(&nv_encoder->outp, nv_crtc->index, true, max_ac_packet, rekey,
 			     mode->clock, hdmi->scdc.supported, hdmi->scdc.scrambling.supported,
 			     hdmi->scdc.scrambling.low_rates);
-	if (ret)
+	if (ret < 0) {
+		NV_ERROR(drm, "Failure to set HDMI: %d\n", ret);
 		return;
-
+	}
+	
 	/* AVI InfoFrame. */
 	args->version = 0;
 	args->head = nv_crtc->index;
diff '--color=auto' -ur a/drivers/gpu/drm/nouveau/nvkm/engine/disp/uoutp.c b/drivers/gpu/drm/nouveau/nvkm/engine/disp/uoutp.c
--- a/drivers/gpu/drm/nouveau/nvkm/engine/disp/uoutp.c	2025-11-30 23:42:10.000000000 +0100
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/disp/uoutp.c	2026-01-17 01:20:03.670240977 +0100
@@ -253,8 +253,7 @@
 
 	if (!ior->func->hdmi ||
 	    args->v0.max_ac_packet > 0x1f ||
-	    args->v0.rekey > 0x7f ||
-	    (args->v0.scdc && !ior->func->hdmi->scdc))
+	    args->v0.rekey > 0x7f)
 		return -EINVAL;
 
 	if (!args->v0.enable) {
@@ -266,6 +265,11 @@
 
 	ior->func->hdmi->ctrl(ior, args->v0.head, args->v0.enable,
 			      args->v0.max_ac_packet, args->v0.rekey);
+	
+	if (args->v0.scdc && !ior->func->hdmi->scdc)
+		OUTP_DBG(outp, "SCDC enabled: %d, ior->func->hdmi->scdc not implemented (ior): %p", 
+				      args->v0.scdc, ior);
+
 	if (ior->func->hdmi->scdc)
 		ior->func->hdmi->scdc(ior, args->v0.khz, args->v0.scdc, args->v0.scdc_scrambling,
 				      args->v0.scdc_low_rates);