[PATCH RFC 1/8] drm/bridge: dw-hdmi: Add SCDC and TMDS Scrambling support

[narmstrong@baylibre.com (Neil Armstrong)]

Add support for SCDC Setup for TMDS Clock > 3.4GHz and enable TMDS
Scrambling when supported or mandatory.

This patch also adds an helper to setup the control bit to support
the hight TMDS Bit Period/TMDS Clock-Period Ratio as required with
TMDS Clock > 3.4GHz for HDMI2.0 3840x2160 at 60/50 modes.

These changes were based on work done by Huicong Xu <xhc@rock-chips.com>
and Nickey Yang <nickey.yang@rock-chips.com> to support HDMI2.0 modes
on the Rockchip 4.4 BSP kernel at [1]

[1] https://github.com/rockchip-linux/kernel/tree/release-4.4

Cc: Nickey Yang <nickey.yang@rock-chips.com>
Cc: Huicong Xu <xhc@rock-chips.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 45 +++++++++++++++++++++--
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.h |  1 +
 include/drm/bridge/dw_hdmi.h              |  1 +
 3 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 5971976284bf..523508af70b0 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -28,6 +28,7 @@
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_encoder_slave.h>
+#include <drm/drm_scdc_helper.h>
 #include <drm/bridge/dw_hdmi.h>
 
 #include <uapi/linux/media-bus-format.h>
@@ -1015,6 +1016,20 @@ void dw_hdmi_phy_i2c_write(struct dw_hdmi *hdmi, unsigned short data,
 }
 EXPORT_SYMBOL_GPL(dw_hdmi_phy_i2c_write);
 
+void dw_hdmi_set_high_tmds_clock_ratio(struct dw_hdmi *hdmi)
+{
+	unsigned long mtmdsclock = hdmi->hdmi_data.video_mode.mpixelclock;
+
+	/* Control for TMDS Bit Period/TMDS Clock-Period Ratio */
+	if (hdmi->connector.display_info.hdmi.scdc.supported) {
+		if (mtmdsclock > 340000000)
+			drm_scdc_set_high_tmds_clock_ratio(hdmi->ddc, 1);
+		else
+			drm_scdc_set_high_tmds_clock_ratio(hdmi->ddc, 0);
+	}
+}
+EXPORT_SYMBOL_GPL(dw_hdmi_set_high_tmds_clock_ratio);
+
 static void dw_hdmi_phy_enable_powerdown(struct dw_hdmi *hdmi, bool enable)
 {
 	hdmi_mask_writeb(hdmi, !enable, HDMI_PHY_CONF0,
@@ -1340,11 +1355,12 @@ static void hdmi_tx_hdcp_config(struct dw_hdmi *hdmi)
 
 static void hdmi_config_AVI(struct dw_hdmi *hdmi, struct drm_display_mode *mode)
 {
+	bool is_hdmi2_sink = hdmi->connector.display_info.hdmi.scdc.supported;
 	struct hdmi_avi_infoframe frame;
 	u8 val;
 
 	/* Initialise info frame from DRM mode */
-	drm_hdmi_avi_infoframe_from_display_mode(&frame, mode, false);
+	drm_hdmi_avi_infoframe_from_display_mode(&frame, mode, is_hdmi2_sink);
 
 	if (hdmi_bus_fmt_is_yuv444(hdmi->hdmi_data.enc_out_bus_format))
 		frame.colorspace = HDMI_COLORSPACE_YUV444;
@@ -1503,7 +1519,8 @@ static void hdmi_config_vendor_specific_infoframe(struct dw_hdmi *hdmi,
 static void hdmi_av_composer(struct dw_hdmi *hdmi,
 			     const struct drm_display_mode *mode)
 {
-	u8 inv_val;
+	u8 inv_val, bytes;
+	struct drm_hdmi_info *hdmi_info = &hdmi->connector.display_info.hdmi;
 	struct hdmi_vmode *vmode = &hdmi->hdmi_data.video_mode;
 	int hblank, vblank, h_de_hs, v_de_vs, hsync_len, vsync_len;
 	unsigned int vdisplay;
@@ -1513,7 +1530,9 @@ static void hdmi_av_composer(struct dw_hdmi *hdmi,
 	dev_dbg(hdmi->dev, "final pixclk = %d\n", vmode->mpixelclock);
 
 	/* Set up HDMI_FC_INVIDCONF */
-	inv_val = (hdmi->hdmi_data.hdcp_enable ?
+	inv_val = (hdmi->hdmi_data.hdcp_enable ||
+		   vmode->mpixelclock > 340000000 ||
+		   hdmi_info->scdc.scrambling.low_rates ?
 		HDMI_FC_INVIDCONF_HDCP_KEEPOUT_ACTIVE :
 		HDMI_FC_INVIDCONF_HDCP_KEEPOUT_INACTIVE);
 
@@ -1562,6 +1581,26 @@ static void hdmi_av_composer(struct dw_hdmi *hdmi,
 		vsync_len /= 2;
 	}
 
+	/* Scrambling Control */
+	if (hdmi_info->scdc.supported) {
+		if (vmode->mpixelclock > 340000000 ||
+		    hdmi_info->scdc.scrambling.low_rates) {
+			drm_scdc_readb(&hdmi->i2c->adap, SCDC_SINK_VERSION,
+				       &bytes);
+			drm_scdc_writeb(&hdmi->i2c->adap, SCDC_SOURCE_VERSION,
+					bytes);
+			drm_scdc_set_scrambling(&hdmi->i2c->adap, 1);
+			hdmi_writeb(hdmi, (u8)~HDMI_MC_SWRSTZ_TMDSSWRST_REQ,
+				    HDMI_MC_SWRSTZ);
+			hdmi_writeb(hdmi, 1, HDMI_FC_SCRAMBLER_CTRL);
+		} else {
+			hdmi_writeb(hdmi, 0, HDMI_FC_SCRAMBLER_CTRL);
+			hdmi_writeb(hdmi, (u8)~HDMI_MC_SWRSTZ_TMDSSWRST_REQ,
+				    HDMI_MC_SWRSTZ);
+			drm_scdc_set_scrambling(&hdmi->i2c->adap, 0);
+		}
+	}
+
 	/* Set up horizontal active pixel width */
 	hdmi_writeb(hdmi, mode->hdisplay >> 8, HDMI_FC_INHACTV1);
 	hdmi_writeb(hdmi, mode->hdisplay, HDMI_FC_INHACTV0);
diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
index 9d90eb9c46e5..3f3c616eba97 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
@@ -255,6 +255,7 @@
 #define HDMI_FC_MASK2                           0x10DA
 #define HDMI_FC_POL2                            0x10DB
 #define HDMI_FC_PRCONF                          0x10E0
+#define HDMI_FC_SCRAMBLER_CTRL                  0x10E1
 
 #define HDMI_FC_GMD_STAT                        0x1100
 #define HDMI_FC_GMD_EN                          0x1101
diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
index ccb5aa8468e0..d7cc5d094270 100644
--- a/include/drm/bridge/dw_hdmi.h
+++ b/include/drm/bridge/dw_hdmi.h
@@ -156,6 +156,7 @@ void dw_hdmi_setup_rx_sense(struct dw_hdmi *hdmi, bool hpd, bool rx_sense);
 void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, unsigned int rate);
 void dw_hdmi_audio_enable(struct dw_hdmi *hdmi);
 void dw_hdmi_audio_disable(struct dw_hdmi *hdmi);
+void dw_hdmi_set_high_tmds_clock_ratio(struct dw_hdmi *hdmi);
 
 /* PHY configuration */
 void dw_hdmi_phy_i2c_set_addr(struct dw_hdmi *hdmi, u8 address);
-- 
2.19.1