Re: [PATCH v2 1/2] drm/i915/icl: Set GCP_COLOR_INDICATION only for 10/12 bit deep color

[Clinton Taylor <Clinton.A.Taylor@intel.com>]

On 4/2/19 8:54 AM, Clinton Taylor wrote:
>
> 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.Taylor@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.

After double checking BSPEC (50524) this behavior appears to be as as 
designed. Under Restriction for bit 2: This bit must be set when in HDMI 
deep color (>8 BPC) mode. I don't agree with this restriction as 8 bit 
is a valid GCP indication.

-Clint


>
> We will file a SI bug against the current behavior.
>
> -Clint
>
>
>>
>>> Signed-off-by: Clinton Taylor <Clinton.A.Taylor@intel.com>
>>> Signed-off-by: Aditya Swarup <aditya.swarup@intel.com>
>>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> Cc: Jani Nikula <jani.nikula@intel.com>
>>> Cc: Manasi Navare <manasi.d.navare@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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