[Nouveau] [PATCH v2 1/2] disp: activate dual link TMDS links only when possible

[Ilia Mirkin]

From: Hauke Mehrtens <hauke at hauke-m.de>

Without this patch a pixel clock rate above 165 MHz on a TMDS link is
assumed to be dual link. This is true for DVI, but not for HDMI. HDMI
supports no dual link, but it supports pixel clock rates above 165 MHz.
Only activate Dual Link mode when it is actually possible and requested.

Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
[imirkin: check for hdmi monitor for computing proto, use sor ctrl to
 enable extra config bit]
Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---
 drm/nouveau/nv50_display.c           | 18 ++++++++++++++----
 drm/nouveau/nvkm/engine/disp/gf119.c |  2 +-
 drm/nouveau/nvkm/engine/disp/nv50.c  |  2 +-
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/drm/nouveau/nv50_display.c b/drm/nouveau/nv50_display.c
index c053c50..57781fd 100644
--- a/drm/nouveau/nv50_display.c
+++ b/drm/nouveau/nv50_display.c
@@ -1961,10 +1961,20 @@ nv50_sor_mode_set(struct drm_encoder *encoder, struct drm_display_mode *umode,
 	switch (nv_encoder->dcb->type) {
 	case DCB_OUTPUT_TMDS:
 		if (nv_encoder->dcb->sorconf.link & 1) {
-			if (mode->clock < 165000)
-				proto = 0x1;
-			else
-				proto = 0x5;
+			proto = 0x1;
+			/* Only enable dual-link if:
+			 *  - DCB says we can
+			 *  - Need to (i.e. rate > 165MHz)
+			 *  - Not an HDMI monitor, since there's no dual-link
+			 *    on HDMI. Of course in order to determine that,
+			 *    we need the EDID. So if no EDID, just let it
+			 *    slide.
+			 */
+			if (mode->clock >= 165000 &&
+			    nv_encoder->dcb->duallink_possible &&
+			    (!nv_connector->edid ||
+			     !drm_detect_hdmi_monitor(nv_connector->edid)))
+				proto |= 0x4;
 		} else {
 			proto = 0x2;
 		}
diff --git a/drm/nouveau/nvkm/engine/disp/gf119.c b/drm/nouveau/nvkm/engine/disp/gf119.c
index 186fd3a..f031466 100644
--- a/drm/nouveau/nvkm/engine/disp/gf119.c
+++ b/drm/nouveau/nvkm/engine/disp/gf119.c
@@ -158,7 +158,7 @@ exec_clkcmp(struct nv50_disp *disp, int head, int id, u32 pclk, u32 *conf)
 	switch (outp->info.type) {
 	case DCB_OUTPUT_TMDS:
 		*conf = (ctrl & 0x00000f00) >> 8;
-		if (pclk >= 165000)
+		if (*conf == 5)
 			*conf |= 0x0100;
 		break;
 	case DCB_OUTPUT_LVDS:
diff --git a/drm/nouveau/nvkm/engine/disp/nv50.c b/drm/nouveau/nvkm/engine/disp/nv50.c
index 32e73a9..4226d21 100644
--- a/drm/nouveau/nvkm/engine/disp/nv50.c
+++ b/drm/nouveau/nvkm/engine/disp/nv50.c
@@ -391,7 +391,7 @@ exec_clkcmp(struct nv50_disp *disp, int head, int id, u32 pclk, u32 *conf)
 		switch (outp->info.type) {
 		case DCB_OUTPUT_TMDS:
 			*conf = (ctrl & 0x00000f00) >> 8;
-			if (pclk >= 165000)
+			if (*conf == 5)
 				*conf |= 0x0100;
 			break;
 		case DCB_OUTPUT_LVDS:
-- 
2.4.10