On 4/2/19 5:53 AM, Ville Syrjälä wrote:
On Tue, Apr 02, 2019 at 05:14:39AM -0700, Aditya Swarup wrote:
From: Clinton Taylor <clinton.a.tay...@intel.com>

v2: Fix commit msg to reflect why issue occurs(Jani)
Set GCP_COLOR_INDICATION only when we set 10/12 bit deep color.

Changing settings from 10/12 bit deep color to 8 bit(& vice versa)
doesn't work correctly using xrandr max bpc property. When we
connect a monitor which supports deep color, the highest deep color
setting is selected; which sets GCP_COLOR_INDICATION. When we change
the setting to 8 bit color, we still set GCP_COLOR_INDICATION which
doesn't allow the switch back to 8 bit color.
Why not? Table 6-1 in HDMI 1.4a spec clearly lists 8bpc as a
valid setting for GCP.

This appears to be a undocumented SI issue. According to the spec 8 bit is a valid GCP value. However, if you enable GCP indication and 8 bit is current then 10 bit is transmit via GCP confusing monitors. The GCP is being validated using 2 different HDMI Analyzer's confirming the results.

We will file a SI bug against the current behavior.

-Clint



Signed-off-by: Clinton Taylor <clinton.a.tay...@intel.com>
Signed-off-by: Aditya Swarup <aditya.swa...@intel.com>
Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
Cc: Jani Nikula <jani.nik...@intel.com>
Cc: Manasi Navare <manasi.d.nav...@intel.com>
---
  drivers/gpu/drm/i915/intel_hdmi.c | 31 +++++++++++++++----------------
  1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_hdmi.c 
b/drivers/gpu/drm/i915/intel_hdmi.c
index 5ccb305a6e1c..4760462f84ca 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -963,7 +963,9 @@ static void intel_hdmi_compute_gcp_infoframe(struct 
intel_encoder *encoder,
                intel_hdmi_infoframe_enable(HDMI_PACKET_TYPE_GENERAL_CONTROL);
/* Indicate color depth whenever the sink supports deep color */
-       if (hdmi_sink_is_deep_color(conn_state))
+
+       if (hdmi_sink_is_deep_color(conn_state) &&
+           (crtc_state->pipe_bpp > 24))
                crtc_state->infoframes.gcp |= GCP_COLOR_INDICATION;
/* Enable default_phase whenever the display mode is suitably aligned */
@@ -2260,6 +2262,7 @@ int intel_hdmi_compute_config(struct intel_encoder 
*encoder,
        int clock_8bpc = pipe_config->base.adjusted_mode.crtc_clock;
        int clock_10bpc = clock_8bpc * 5 / 4;
        int clock_12bpc = clock_8bpc * 3 / 2;
+       int dc_clock = clock_12bpc;
        int desired_bpp;
        bool force_dvi = intel_conn_state->force_audio == HDMI_AUDIO_OFF_DVI;
@@ -2314,22 +2317,18 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
         * Note that g4x/vlv don't support 12bpc hdmi outputs. We also need
         * to check that the higher clock still fits within limits.
         */
-       if (hdmi_deep_color_possible(pipe_config, 12) &&
-           hdmi_port_clock_valid(intel_hdmi, clock_12bpc,
+       if (pipe_config->pipe_bpp == 30)
+               dc_clock = clock_10bpc;
+
+       if (hdmi_deep_color_possible(pipe_config, pipe_config->pipe_bpp / 3) &&
+           hdmi_port_clock_valid(intel_hdmi, dc_clock,
                                  true, force_dvi) == MODE_OK) {
-               DRM_DEBUG_KMS("picking bpc to 12 for HDMI output\n");
-               desired_bpp = 12*3;
-
-               /* Need to adjust the port link by 1.5x for 12bpc. */
-               pipe_config->port_clock = clock_12bpc;
-       } else if (hdmi_deep_color_possible(pipe_config, 10) &&
-                  hdmi_port_clock_valid(intel_hdmi, clock_10bpc,
-                                        true, force_dvi) == MODE_OK) {
-               DRM_DEBUG_KMS("picking bpc to 10 for HDMI output\n");
-               desired_bpp = 10 * 3;
-
-               /* Need to adjust the port link by 1.25x for 10bpc. */
-               pipe_config->port_clock = clock_10bpc;
+               DRM_DEBUG_KMS("picking bpc to %d for HDMI output\n",
+                                pipe_config->pipe_bpp / 3);
+               desired_bpp = pipe_config->pipe_bpp;
+
+               /* Need to adjust the port link dc modes. */
+               pipe_config->port_clock = dc_clock;
This part has nothing to do with the commit message.


        } else {
                DRM_DEBUG_KMS("picking bpc to 8 for HDMI output\n");
                desired_bpp = 8*3;
--
2.17.1
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