Hi Ville,

Thanks for pointing out the issues and suggestions.

I agree with the suggested changes and corrections and will make the changes in the next version.

Regards,

Ankit

On 4/24/2023 6:01 PM, Ville Syrjälä wrote:
On Fri, Mar 31, 2023 at 03:46:03PM +0530, Ankit Nautiyal wrote:
The decision to use DFP output format conversion capabilities should be
during compute_config phase.

This patch uses the members of intel_dp->dfp to only store the
format conversion capabilities of the DP device and uses the crtc_state
sink_format member, to program the protocol-converter for
colorspace/format conversion.

v2: Use sink_format to determine the color conversion config for the
pcon (Ville).

v3: Fix typo: missing 'break' in switch case (lkp kernel test robot).

v4: Add helper to check if DP supports YCBCR420.

v5: Simplify logic for computing output_format, based on the given
sink_format. (Ville).
Added scaler constraint for YCbCr420 output.

v6: Split the patch for Scaler constraint for Ycbcr420.

v7: Simplify the policy for selecting output_format:
Always try for RGB first, followed by YCBCR444, and finally by YCBCR420.

v8: Removed redundant comments, minor refactoring. (Ville)

Signed-off-by: Ankit Nautiyal <ankit.k.nauti...@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
---
  drivers/gpu/drm/i915/display/intel_dp.c | 178 +++++++++++++++++-------
  1 file changed, 125 insertions(+), 53 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c 
b/drivers/gpu/drm/i915/display/intel_dp.c
index 450cb8ba3805..837532952936 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -827,24 +827,92 @@ u8 intel_dp_dsc_get_slice_count(struct intel_dp *intel_dp,
        return 0;
  }
+static bool source_can_output(struct intel_dp *intel_dp,
+                             enum intel_output_format format)
+{
+       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+       bool ycbcr_supported = true;
+
+       /*
+        * No YCbCr output support on gmch platforms.
+        * Also, ILK doesn't seem capable of DP YCbCr output.
+        * The displayed image is severly corrupted. SNB+ is fine.
+        */
+       if (HAS_GMCH(i915) || IS_IRONLAKE(i915))
+               ycbcr_supported = false;
That extra variable seems rather pointless...

+
+       switch (format) {
+       case INTEL_OUTPUT_FORMAT_RGB :
+               return true;
+
+       case INTEL_OUTPUT_FORMAT_YCBCR444:
+               return ycbcr_supported;
could just 'return !GMCH && !ILK' here

+
+       case INTEL_OUTPUT_FORMAT_YCBCR420:
+               /* Platform < Gen 11 cannot output YCbCr420 format */
+               if (!ycbcr_supported || DISPLAY_VER(i915) < 11)
+                       return false;
+
+               return true;
and 'return DISPLAY_VER >= 11' here.

+
+       default:
+               MISSING_CASE(format);
+               return false;
+       }
+}
+
+static bool
+dfp_can_convert_from_rgb(struct intel_dp *intel_dp,
+                        enum intel_output_format sink_format)
+{
+       if (!drm_dp_is_branch(intel_dp->dpcd))
+               return false;
+
+       if (sink_format == INTEL_OUTPUT_FORMAT_YCBCR444)
+               return intel_dp->dfp.rgb_to_ycbcr;
+
+       if (sink_format == INTEL_OUTPUT_FORMAT_YCBCR420)
+               return intel_dp->dfp.rgb_to_ycbcr &&
+                       intel_dp->dfp.ycbcr_444_to_420;
+
+       return false;
+}
+
+static bool
+dfp_can_convert_from_ycbcr444(struct intel_dp *intel_dp,
+                             enum intel_output_format sink_format)
+{
+       if (!drm_dp_is_branch(intel_dp->dpcd))
+               return false;
+
+       if (sink_format == INTEL_OUTPUT_FORMAT_YCBCR420)
+               return intel_dp->dfp.ycbcr_444_to_420;
+
+       return false;
+}
+
  static enum intel_output_format
  intel_dp_output_format(struct intel_connector *connector,
                       enum intel_output_format sink_format)
  {
        struct intel_dp *intel_dp = intel_attached_dp(connector);
+       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+       enum intel_output_format output_format;
- if (!connector->base.ycbcr_420_allowed ||
-           sink_format != INTEL_OUTPUT_FORMAT_YCBCR420)
-               return INTEL_OUTPUT_FORMAT_RGB;
+       if (sink_format == INTEL_OUTPUT_FORMAT_RGB ||
+           dfp_can_convert_from_rgb(intel_dp, sink_format))
+               output_format = INTEL_OUTPUT_FORMAT_RGB;
- if (intel_dp->dfp.rgb_to_ycbcr &&
-           intel_dp->dfp.ycbcr_444_to_420)
-               return INTEL_OUTPUT_FORMAT_RGB;
+       else if (sink_format == INTEL_OUTPUT_FORMAT_YCBCR444 ||
+           dfp_can_convert_from_ycbcr444(intel_dp, sink_format))
+               output_format = INTEL_OUTPUT_FORMAT_YCBCR444;
- if (intel_dp->dfp.ycbcr_444_to_420)
-               return INTEL_OUTPUT_FORMAT_YCBCR444;
        else
-               return INTEL_OUTPUT_FORMAT_YCBCR420;
+               output_format = INTEL_OUTPUT_FORMAT_YCBCR420;
+
+       drm_WARN_ON(&i915->drm, !source_can_output(intel_dp, output_format));
+
+       return output_format;
  }
int intel_dp_min_bpp(enum intel_output_format output_format)
@@ -2761,6 +2829,8 @@ void intel_dp_configure_protocol_converter(struct 
intel_dp *intel_dp,
                                           const struct intel_crtc_state 
*crtc_state)
  {
        struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+       bool ycbcr444_to_420 = false;
+       bool rgb_to_ycbcr = false;
        u8 tmp;
if (intel_dp->dpcd[DP_DPCD_REV] < 0x13)
@@ -2777,8 +2847,24 @@ void intel_dp_configure_protocol_converter(struct 
intel_dp *intel_dp,
                drm_dbg_kms(&i915->drm, "Failed to %s protocol converter HDMI 
mode\n",
                            str_enable_disable(intel_dp->has_hdmi_sink));
- tmp = crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444 &&
-               intel_dp->dfp.ycbcr_444_to_420 ? 
DP_CONVERSION_TO_YCBCR420_ENABLE : 0;
+       if (crtc_state->sink_format == INTEL_OUTPUT_FORMAT_YCBCR420) {
+               switch (crtc_state->output_format) {
+               case INTEL_OUTPUT_FORMAT_YCBCR420:
+                       break;
+               case INTEL_OUTPUT_FORMAT_YCBCR444:
+                       ycbcr444_to_420 = true;
+                       break;
+               case INTEL_OUTPUT_FORMAT_RGB:
+                       rgb_to_ycbcr = true;
+                       ycbcr444_to_420 = true;
+                       break;
+               default:
+                       MISSING_CASE(crtc_state->output_format);
+                       break;
+               }
+       }
+
+       tmp = ycbcr444_to_420 ? DP_CONVERSION_TO_YCBCR420_ENABLE : 0;
if (drm_dp_dpcd_writeb(&intel_dp->aux,
                               DP_PROTOCOL_CONVERTER_CONTROL_1, tmp) != 1)
@@ -2786,13 +2872,12 @@ void intel_dp_configure_protocol_converter(struct 
intel_dp *intel_dp,
                            "Failed to %s protocol converter YCbCr 4:2:0 conversion 
mode\n",
                            str_enable_disable(intel_dp->dfp.ycbcr_444_to_420));
- tmp = intel_dp->dfp.rgb_to_ycbcr ?
-               DP_CONVERSION_BT709_RGB_YCBCR_ENABLE : 0;
+       tmp = rgb_to_ycbcr ? DP_CONVERSION_BT709_RGB_YCBCR_ENABLE : 0;
if (drm_dp_pcon_convert_rgb_to_ycbcr(&intel_dp->aux, tmp) < 0)
                drm_dbg_kms(&i915->drm,
-                          "Failed to %s protocol converter RGB->YCbCr conversion 
mode\n",
-                          str_enable_disable(tmp));
+                           "Failed to %s protocol converter RGB->YCbCr conversion 
mode\n",
+                           str_enable_disable(tmp));
  }
bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp)
@@ -4582,57 +4667,44 @@ intel_dp_update_dfp(struct intel_dp *intel_dp,
        intel_dp_get_pcon_dsc_cap(intel_dp);
  }
+static bool
+intel_dp_can_ycbcr420(struct intel_dp *intel_dp)
+{
+       if (source_can_output(intel_dp, INTEL_OUTPUT_FORMAT_YCBCR420) &&
+           (!drm_dp_is_branch(intel_dp->dpcd) || 
intel_dp->dfp.ycbcr420_passthrough))
+               return true;
+
+       if (source_can_output(intel_dp, INTEL_OUTPUT_FORMAT_RGB) &&
+           dfp_can_convert_from_rgb(intel_dp, INTEL_OUTPUT_FORMAT_YCBCR420))
+               return true;
+
+       if (source_can_output(intel_dp, INTEL_OUTPUT_FORMAT_YCBCR444) &&
+           dfp_can_convert_from_ycbcr444(intel_dp, 
INTEL_OUTPUT_FORMAT_YCBCR420))
+               return INTEL_OUTPUT_FORMAT_YCBCR444;
return true

The rest looks good.

+
+       return false;
+}
+
  static void
  intel_dp_update_420(struct intel_dp *intel_dp)
  {
        struct drm_i915_private *i915 = dp_to_i915(intel_dp);
        struct intel_connector *connector = intel_dp->attached_connector;
-       bool is_branch, ycbcr_420_passthrough, ycbcr_444_to_420, rgb_to_ycbcr;
-
-       /* No YCbCr output support on gmch platforms */
-       if (HAS_GMCH(i915))
-               return;
- /*
-        * ILK doesn't seem capable of DP YCbCr output. The
-        * displayed image is severly corrupted. SNB+ is fine.
-        */
-       if (IS_IRONLAKE(i915))
-               return;
-
-       is_branch = drm_dp_is_branch(intel_dp->dpcd);
-       ycbcr_420_passthrough =
+       intel_dp->dfp.ycbcr420_passthrough =
                drm_dp_downstream_420_passthrough(intel_dp->dpcd,
                                                  intel_dp->downstream_ports);
        /* on-board LSPCON always assumed to support 4:4:4->4:2:0 conversion */
-       ycbcr_444_to_420 =
+       intel_dp->dfp.ycbcr_444_to_420 =
                dp_to_dig_port(intel_dp)->lspcon.active ||
                drm_dp_downstream_444_to_420_conversion(intel_dp->dpcd,
                                                        
intel_dp->downstream_ports);
-       rgb_to_ycbcr = drm_dp_downstream_rgb_to_ycbcr_conversion(intel_dp->dpcd,
-                                                                
intel_dp->downstream_ports,
-                                                                
DP_DS_HDMI_BT709_RGB_YCBCR_CONV);
-
-       if (DISPLAY_VER(i915) >= 11) {
-               /* Let PCON convert from RGB->YCbCr if possible */
-               if (is_branch && rgb_to_ycbcr && ycbcr_444_to_420) {
-                       intel_dp->dfp.rgb_to_ycbcr = true;
-                       intel_dp->dfp.ycbcr_444_to_420 = true;
-                       connector->base.ycbcr_420_allowed = true;
-               } else {
-               /* Prefer 4:2:0 passthrough over 4:4:4->4:2:0 conversion */
-                       intel_dp->dfp.ycbcr_444_to_420 =
-                               ycbcr_444_to_420 && !ycbcr_420_passthrough;
+       intel_dp->dfp.rgb_to_ycbcr =
+               drm_dp_downstream_rgb_to_ycbcr_conversion(intel_dp->dpcd,
+                                                         
intel_dp->downstream_ports,
+                                                         
DP_DS_HDMI_BT709_RGB_YCBCR_CONV);
- connector->base.ycbcr_420_allowed =
-                               !is_branch || ycbcr_444_to_420 || 
ycbcr_420_passthrough;
-               }
-       } else {
-               /* 4:4:4->4:2:0 conversion is the only way */
-               intel_dp->dfp.ycbcr_444_to_420 = ycbcr_444_to_420;
-
-               connector->base.ycbcr_420_allowed = ycbcr_444_to_420;
-       }
+       connector->base.ycbcr_420_allowed = intel_dp_can_ycbcr420(intel_dp);
drm_dbg_kms(&i915->drm,
                    "[CONNECTOR:%d:%s] RGB->YcbCr conversion? %s, YCbCr 4:2:0 allowed? 
%s, YCbCr 4:4:4->4:2:0 conversion? %s\n",
--
2.25.1

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