Regards

Shashank


On 2/2/2018 12:39 AM, Ville Syrjälä wrote:
On Tue, Jan 30, 2018 at 03:06:03PM +0530, Shashank Sharma wrote:
From: "Sharma, Shashank" <shashank.sha...@intel.com>

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.syrj...@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
Signed-off-by: Shashank Sharma <shashank.sha...@intel.com>
---
  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;
I really don't like the name of that. Makes me think we're actually
scaling the entire output or something. 'external_ycbcr_420_downsample'
or something like that would be better.
ok, let me rename this to something in those lines.
        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;
Why split the work between two functions like this? I think it would be
cleaner to either inline all the code here, or move it all into
lspcon_ycbcr420_config().
Sure, makes sense.
+               }
+       }
+
        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)
crtc_state
ok

+{
+       struct drm_display_info *info = &connector->display_info;
const
ok
+       struct drm_display_mode *mode = &config->base.adjusted_mode;
const ... adjusted_mode;
ok
+
+       if (drm_mode_is_420_only(info, mode)) {
+               if (!connector->ycbcr_420_allowed) {
+                       DRM_ERROR("Platform doesn't support YCBCR420 output\n");
+                       return false;
How can we even get here?
This code flow is coming from CRTC/encoder side, whereas 420 capability is set in connector_init, this is the first time we are checking connector's capabilities. So yes, its possible to reach here.
- Shashank
+               }
+
+               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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