[PATCH v4 7/7] drm/i915: Add YCBCR 4:2:0/4:4:4 support for LSPCON

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From: "Sharma, Shashank" <shashank.sharma@xxxxxxxxx>

LSPCON chips can generate YCBCR outputs, if asked nicely :).

In order to generate YCBCR 4:2:0 outputs, a source must:
- send YCBCR 4:4:4 signals to LSPCON
- program color space as 4:2:0 in AVI infoframes

Whereas for YCBCR 4:4:4 outputs, the source must:
- send YCBCR 4:4:4 signals to LSPCON
- program color space as 4:4:4 in AVI infoframes

So for both 4:2:0 as well as 4:4:4 outputs, we are driving the
pipe for YCBCR 4:4:4 output, but AVI infoframe's color space
information indicates LSPCON FW to start scaling down from YCBCR
4:4:4 and generate YCBCR 4:2:0 output. As the scaling is done by
LSPCON device, we need not to reserve a scaler for 4:2:0 outputs.

V2: rebase
V3: Addressed review comments from Ville
    - add enum crtc_output_format instead of bool ycbcr420
    - use crtc_output_format=4:4:4 for modeset of LSPCON 4:2:0 output
      cases in this way we will have YCBCR 4:4:4 framework ready (except
      the ABI part)
V4: Added r-b from Maarten (for v3)
    Addressed review comments from Ville:
    - Do not add a non-atomic state variable to determine lspcon output.
      Instead add bool in CRTC state to indicate lspcon based scaling.

Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Signed-off-by: Shashank Sharma <shashank.sharma@xxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_reg.h      |  2 ++
 drivers/gpu/drm/i915/intel_ddi.c     |  7 +++++++
 drivers/gpu/drm/i915/intel_display.c | 11 ++++++++++-
 drivers/gpu/drm/i915/intel_dp.c      | 10 ++++++++++
 drivers/gpu/drm/i915/intel_drv.h     |  5 +++++
 drivers/gpu/drm/i915/intel_lspcon.c  | 30 ++++++++++++++++++++++++++++++
 6 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 64933fd..e383b05 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -8721,6 +8721,8 @@ enum skl_power_gate {
 #define TRANS_MSA_MISC(tran) _MMIO_TRANS2(tran, _TRANSA_MSA_MISC)
 
 #define  TRANS_MSA_SYNC_CLK		(1<<0)
+#define  TRANS_MSA_SAMPLING_444        (2<<1)
+#define  TRANS_MSA_CLRSP_YCBCR		(2<<3)
 #define  TRANS_MSA_6_BPC		(0<<5)
 #define  TRANS_MSA_8_BPC		(1<<5)
 #define  TRANS_MSA_10_BPC		(2<<5)
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 510bb77..db7d940 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1499,6 +1499,13 @@ void intel_ddi_set_pipe_settings(const struct intel_crtc_state *crtc_state)
 		break;
 	}
 
+	/*
+	 * As per DP 1.2 spec section 2.3.4.3 while sending
+	 * YCBCR 444 signals we should program MSA MISC1/0 fields with
+	 * colorspace information. The output colorspace encoding is BT601.
+	 */
+	if (crtc_state->output_format == CRTC_OUTPUT_YCBCR444)
+		temp |= TRANS_MSA_SAMPLING_444 | TRANS_MSA_CLRSP_YCBCR;
 	I915_WRITE(TRANS_MSA_MISC(cpu_transcoder), temp);
 }
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 4a40de9..b26f4a9 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9228,6 +9228,7 @@ static bool haswell_get_pipe_config(struct intel_crtc *crtc,
 	pipe_config->gamma_mode =
 		I915_READ(GAMMA_MODE(crtc->pipe)) & GAMMA_MODE_MODE_MASK;
 
+	pipe_config->external_scaling = false;
 	if (IS_BROADWELL(dev_priv) || INTEL_GEN(dev_priv) >= 9) {
 		u32 tmp = I915_READ(PIPEMISC(crtc->pipe));
 		enum intel_output_format output_format = CRTC_OUTPUT_RGB;
@@ -9247,8 +9248,16 @@ static bool haswell_get_pipe_config(struct intel_crtc *crtc,
 					output_format = CRTC_OUTPUT_YCBCR420;
 			} else {
 				output_format = CRTC_OUTPUT_YCBCR444;
-			}
 
+				/*
+				 * As there is no interface defined (yet)
+				 * to get the user's preference for output
+				 * format, YCBCR444 output format is only
+				 * possible with LSPCON YCBCR420 output,
+				 * which uses LSPCON's (external )scaler.
+				 */
+				pipe_config->external_scaling = true;
+			}
 		}
 
 		pipe_config->output_format = output_format;
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index a2e8879..be19579 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1640,6 +1640,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
+	struct intel_lspcon *lspcon = enc_to_intel_lspcon(&encoder->base);
 	enum port port = encoder->port;
 	struct intel_crtc *intel_crtc = to_intel_crtc(pipe_config->base.crtc);
 	struct intel_connector *intel_connector = intel_dp->attached_connector;
@@ -1669,6 +1670,15 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	if (HAS_PCH_SPLIT(dev_priv) && !HAS_DDI(dev_priv) && port != PORT_A)
 		pipe_config->has_pch_encoder = true;
 
+	if (lspcon->active) {
+		struct drm_connector *connector = &intel_connector->base;
+
+		if (lspcon_ycbcr420_config(connector, pipe_config)) {
+			pipe_config->output_format = CRTC_OUTPUT_YCBCR444;
+			pipe_config->external_scaling = true;
+		}
+	}
+
 	pipe_config->has_drrs = false;
 	if (IS_G4X(dev_priv) || port == PORT_A)
 		pipe_config->has_audio = false;
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index efaa331..f23129b 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -882,6 +882,9 @@ struct intel_crtc_state {
 
 	/* Output format RGB/YCBCR etc */
 	enum intel_output_format output_format;
+
+	/* Output up/down scaling is done in external device */
+	bool external_scaling;
 };
 
 struct intel_crtc {
@@ -2139,6 +2142,8 @@ void lspcon_set_infoframes(struct drm_encoder *encoder,
 			   const struct drm_connector_state *conn_state);
 bool lspcon_infoframe_enabled(struct drm_encoder *encoder,
 			      const struct intel_crtc_state *pipe_config);
+bool lspcon_ycbcr420_config(struct drm_connector *connector,
+			     struct intel_crtc_state *config);
 
 /* intel_pipe_crc.c */
 int intel_pipe_crc_create(struct drm_minor *minor);
diff --git a/drivers/gpu/drm/i915/intel_lspcon.c b/drivers/gpu/drm/i915/intel_lspcon.c
index 066ea91..8d6a9b2 100644
--- a/drivers/gpu/drm/i915/intel_lspcon.c
+++ b/drivers/gpu/drm/i915/intel_lspcon.c
@@ -180,6 +180,25 @@ static bool lspcon_wake_native_aux_ch(struct intel_lspcon *lspcon)
 	return true;
 }
 
+bool lspcon_ycbcr420_config(struct drm_connector *connector,
+			     struct intel_crtc_state *config)
+{
+	struct drm_display_info *info = &connector->display_info;
+	struct drm_display_mode *mode = &config->base.adjusted_mode;
+
+	if (drm_mode_is_420_only(info, mode)) {
+		if (!connector->ycbcr_420_allowed) {
+			DRM_ERROR("Platform doesn't support YCBCR420 output\n");
+			return false;
+		}
+
+		config->port_clock /= 2;
+		return true;
+	}
+
+	return false;
+}
+
 static bool lspcon_probe(struct intel_lspcon *lspcon)
 {
 	int retry;
@@ -459,6 +478,15 @@ void lspcon_set_infoframes(struct drm_encoder *encoder,
 		return;
 	}
 
+	if (crtc_state->output_format == CRTC_OUTPUT_YCBCR444) {
+		if (crtc_state->external_scaling)
+			frame.avi.colorspace = HDMI_COLORSPACE_YUV420;
+		else
+			frame.avi.colorspace = HDMI_COLORSPACE_YUV444;
+	} else {
+		frame.avi.colorspace = HDMI_COLORSPACE_RGB;
+	}
+
 	drm_hdmi_avi_infoframe_quant_range(&frame.avi, mode,
 					   crtc_state->limited_color_range ?
 					   HDMI_QUANTIZATION_RANGE_LIMITED :
@@ -512,6 +540,7 @@ bool lspcon_init(struct intel_digital_port *intel_dig_port)
 	struct intel_lspcon *lspcon = &intel_dig_port->lspcon;
 	struct drm_device *dev = intel_dig_port->base.base.dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct drm_connector *connector = &dp->attached_connector->base;
 
 	if (!HAS_LSPCON(dev_priv)) {
 		DRM_ERROR("LSPCON is not supported on this platform\n");
@@ -536,6 +565,7 @@ bool lspcon_init(struct intel_digital_port *intel_dig_port)
 		return false;
 	}
 
+	connector->ycbcr_420_allowed = true;
 	lspcon->active = true;
 	DRM_DEBUG_KMS("Success: LSPCON init\n");
 	return true;
-- 
2.7.4

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