drm/nouveau/disp: add support for setting scdc parameters for high modes

When SCDC is supported, make sure that we configure the GPU and monitor
to the same parameters.
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/dispnv50/disp.c

@@ -36,6 +36,7 @@
 #include <drm/drm_dp_helper.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_plane_helper.h>
+#include <drm/drm_scdc_helper.h>
 #include <drm/drm_edid.h>
 
 #include <nvif/class.h>
@@ -531,6 +532,7 @@ nv50_hdmi_disable(struct drm_encoder *encoder, struct nouveau_crtc *nv_crtc)
 static void
 nv50_hdmi_enable(struct drm_encoder *encoder, struct drm_display_mode *mode)
 {
+	struct nouveau_drm *drm = nouveau_drm(encoder->dev);
 	struct nouveau_encoder *nv_encoder = nouveau_encoder(encoder);
 	struct nouveau_crtc *nv_crtc = nouveau_crtc(encoder->crtc);
 	struct nv50_disp *disp = nv50_disp(encoder->dev);
@@ -548,9 +550,12 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct drm_display_mode *mode)
 		.pwr.rekey = 56, /* binary driver, and tegra, constant */
 	};
 	struct nouveau_connector *nv_connector;
+	struct drm_hdmi_info *hdmi;
 	u32 max_ac_packet;
 	union hdmi_infoframe avi_frame;
 	union hdmi_infoframe vendor_frame;
+	bool scdc_supported, high_tmds_clock_ratio = false, scrambling = false;
+	u8 config;
 	int ret;
 	int size;
 
@@ -558,8 +563,11 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct drm_display_mode *mode)
 	if (!drm_detect_hdmi_monitor(nv_connector->edid))
 		return;
 
+	hdmi = &nv_connector->base.display_info.hdmi;
+	scdc_supported = hdmi->scdc.supported;
+
 	ret = drm_hdmi_avi_infoframe_from_display_mode(&avi_frame.avi, mode,
-						       false);
+						       scdc_supported);
 	if (!ret) {
 		/* We have an AVI InfoFrame, populate it to the display */
 		args.pwr.avi_infoframe_length
@@ -582,12 +590,42 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct drm_display_mode *mode)
 	max_ac_packet -= 18; /* constant from tegra */
 	args.pwr.max_ac_packet = max_ac_packet / 32;
 
+	if (hdmi->scdc.scrambling.supported) {
+		high_tmds_clock_ratio = mode->clock > 340000;
+		scrambling = high_tmds_clock_ratio ||
+			hdmi->scdc.scrambling.low_rates;
+	}
+
+	args.pwr.scdc =
+		NV50_DISP_SOR_HDMI_PWR_V0_SCDC_SCRAMBLE * scrambling |
+		NV50_DISP_SOR_HDMI_PWR_V0_SCDC_DIV_BY_4 * high_tmds_clock_ratio;
+
 	size = sizeof(args.base)
 		+ sizeof(args.pwr)
 		+ args.pwr.avi_infoframe_length
 		+ args.pwr.vendor_infoframe_length;
 	nvif_mthd(&disp->disp->object, 0, &args, size);
+
 	nv50_audio_enable(encoder, mode);
+
+	/* If SCDC is supported by the downstream monitor, update
+	 * divider / scrambling settings to what we programmed above.
+	 */
+	if (!hdmi->scdc.scrambling.supported)
+		return;
+
+	ret = drm_scdc_readb(nv_encoder->i2c, SCDC_TMDS_CONFIG, &config);
+	if (ret < 0) {
+		NV_ERROR(drm, "Failure to read SCDC_TMDS_CONFIG: %d\n", ret);
+		return;
+	}
+	config &= ~(SCDC_TMDS_BIT_CLOCK_RATIO_BY_40 | SCDC_SCRAMBLING_ENABLE);
+	config |= SCDC_TMDS_BIT_CLOCK_RATIO_BY_40 * high_tmds_clock_ratio;
+	config |= SCDC_SCRAMBLING_ENABLE * scrambling;
+	ret = drm_scdc_writeb(nv_encoder->i2c, SCDC_TMDS_CONFIG, config);
+	if (ret < 0)
+		NV_ERROR(drm, "Failure to write SCDC_TMDS_CONFIG = 0x%02x: %d\n",
+			 config, ret);
 }
 
 /******************************************************************************