On Wed, 14 Feb 2024, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
> On Tue, Feb 13, 2024 at 01:30:57PM +0200, Jani Nikula wrote:
>> Rename intel_dp_can_mst() to intel_dp_mst_detect(), and move all DP MST
>> detect debug logging there. Debug log the sink's MST capability,
>> including single-stream sideband messaging support, and the decision
>> whether to enable MST mode or not. Do this regardless of whether we're
>> actually enabling MST or not.
>>
>> Cc: Arun R Murthy <arun.r.murthy@xxxxxxxxx>
>> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/display/intel_dp.c | 45 +++++++++++++++++--------
>> 1 file changed, 31 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index a1c304f451bd..944f566525dd 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -4007,31 +4007,48 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
>> intel_dp->downstream_ports) == 0;
>> }
>>
>> +static const char *intel_dp_mst_mode_str(enum drm_dp_mst_mode mst_mode)
>> +{
>> + if (mst_mode == DRM_DP_SST_SIDEBAND_MSG)
>> + return "single-stream sideband messaging";
>> + else
>> + return str_yes_no(mst_mode == DRM_DP_MST);
>
> I wonder if this should also just say "sst"/"mst"/"sst sideband" etc.
> Shrug.
>
> Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
I realize there's an issue here.
intel_dp_detect_dpcd() bails out early for !drm_dp_is_branch(), before
the intel_dp_can_mst() call. (Renamed intel_dp_mst_detect() here.)
We'll still happily call intel_dp_configure_mst() later also for
!branch.
We'll need to call intel_dp_mst_detect() earlier and/or somehow combine
these together. I don't think branch devices need to support MST, but I
think MST devices need to support branching. And single-stream sideband
support does not mean branching.
The intention of this patch was to improve MST debug logging, but the
end result is that it reduces it! Auch.
I wonder if we should branch (eh) the detect earlier for eDP, SST and
MST/branch paths. Just to make it easier for our poor brains to follow.
BR,
Jani.
>
>> +}
>> +
>> static bool
>> -intel_dp_can_mst(struct intel_dp *intel_dp)
>> +intel_dp_mst_detect(struct intel_dp *intel_dp)
>> {
>> struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>> + struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
>> + enum drm_dp_mst_mode sink_mst_mode;
>> + enum drm_dp_mst_mode mst_detect;
>> +
>> + sink_mst_mode = drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd);
>> +
>> + if (i915->display.params.enable_dp_mst &&
>> + intel_dp_mst_source_support(intel_dp) &&
>> + sink_mst_mode == DRM_DP_MST)
>> + mst_detect = DRM_DP_MST;
>> + else
>> + mst_detect = DRM_DP_SST;
>>
>> - return i915->display.params.enable_dp_mst &&
>> - intel_dp_mst_source_support(intel_dp) &&
>> - drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) == DRM_DP_MST;
>> + drm_dbg_kms(&i915->drm,
>> + "[ENCODER:%d:%s] MST support: port: %s, sink: %s, modparam: %s -> enable: %s\n",
>> + encoder->base.base.id, encoder->base.name,
>> + str_yes_no(intel_dp_mst_source_support(intel_dp)),
>> + intel_dp_mst_mode_str(sink_mst_mode),
>> + str_yes_no(i915->display.params.enable_dp_mst),
>> + intel_dp_mst_mode_str(mst_detect));
>> +
>> + return mst_detect != DRM_DP_SST;
>> }
>>
>> static void
>> intel_dp_configure_mst(struct intel_dp *intel_dp)
>> {
>> struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>> - struct intel_encoder *encoder =
>> - &dp_to_dig_port(intel_dp)->base;
>> bool sink_can_mst = drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) == DRM_DP_MST;
>>
>> - drm_dbg_kms(&i915->drm,
>> - "[ENCODER:%d:%s] MST support: port: %s, sink: %s, modparam: %s\n",
>> - encoder->base.base.id, encoder->base.name,
>> - str_yes_no(intel_dp_mst_source_support(intel_dp)),
>> - str_yes_no(sink_can_mst),
>> - str_yes_no(i915->display.params.enable_dp_mst));
>> -
>> if (!intel_dp_mst_source_support(intel_dp))
>> return;
>>
>> @@ -5390,7 +5407,7 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
>> connector_status_connected : connector_status_disconnected;
>> }
>>
>> - if (intel_dp_can_mst(intel_dp))
>> + if (intel_dp_mst_detect(intel_dp))
>> return connector_status_connected;
>>
>> /* If no HPD, poke DDC gently */
>> --
>> 2.39.2
--
Jani Nikula, Intel
