drm/nv04/disp: handle dual-link spwg panels without needing quirks

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_bios.c

@@ -4304,18 +4304,6 @@ int nouveau_bios_parse_lvds_table(struct drm_device *dev, int pxclk, bool *dl, b
 		break;
 	}
 
-	/* Dell Latitude D620 reports a too-high value for the dual-link
-	 * transition freq, causing us to program the panel incorrectly.
-	 *
-	 * It doesn't appear the VBIOS actually uses its transition freq
-	 * (90000kHz), instead it uses the "Number of LVDS channels" field
-	 * out of the panel ID structure (http://www.spwg.org/).
-	 *
-	 * For the moment, a quirk will do :)
-	 */
-	if (nv_match_device(dev, 0x01d7, 0x1028, 0x01c2))
-		bios->fp.duallink_transition_clk = 80000;
-
 	/* set dual_link flag for EDID case */
 	if (pxclk && (chip_version < 0x25 || chip_version > 0x28))
 		bios->fp.dual_link = (pxclk >= bios->fp.duallink_transition_clk);

drivers/gpu/drm/nouveau/nv04_dfp.c

@@ -341,10 +341,15 @@ static void nv04_dfp_mode_set(struct drm_encoder *encoder,
 	    output_mode->clock > 165000)
 		regp->fp_control |= (2 << 24);
 	if (nv_encoder->dcb->type == OUTPUT_LVDS) {
-		bool duallink, dummy;
-
+		bool duallink = false, dummy;
+		if (nv_connector->edid &&
+		    nv_connector->type == DCB_CONNECTOR_LVDS_SPWG) {
+			duallink = (((u8 *)nv_connector->edid)[121] == 2);
+		} else {
 			nouveau_bios_parse_lvds_table(dev, output_mode->clock,
 						      &duallink, &dummy);
+		}
+
 		if (duallink)
 			regp->fp_control |= (8 << 28);
 	} else