> -----Original Message-----
> From: Nikula, Jani <jani.nikula@xxxxxxxxx>
> Sent: Tuesday, February 13, 2024 5:01 PM
> To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx; intel-xe@xxxxxxxxxxxxxxxxxxxxx; Nikula, Jani
> <jani.nikula@xxxxxxxxx>; Murthy, Arun R <arun.r.murthy@xxxxxxxxx>; Ville
> Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Subject: [PATCH v2 1/6] drm/mst: read sideband messaging cap
>
> Amend drm_dp_read_mst_cap() to return an enum, indicating "SST", "SST with
> sideband messaging", or "MST". Modify all call sites to take the new return
> value into account.
>
> v2:
> - Rename enumerators (Ville)
>
> 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/display/drm_dp_mst_topology.c | 20 ++++++++++------
> drivers/gpu/drm/i915/display/intel_dp.c | 4 ++--
> drivers/gpu/drm/nouveau/nouveau_dp.c | 2 +-
> include/drm/display/drm_dp_mst_helper.h | 23 ++++++++++++++++++-
> 4 files changed, 38 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index 03d528209426..c193be3577f7 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -3608,24 +3608,30 @@ fixed20_12 drm_dp_get_vc_payload_bw(const
> struct drm_dp_mst_topology_mgr *mgr,
> EXPORT_SYMBOL(drm_dp_get_vc_payload_bw);
>
> /**
> - * drm_dp_read_mst_cap() - check whether or not a sink supports MST
> + * drm_dp_read_mst_cap() - Read the sink's MST mode capability
> * @aux: The DP AUX channel to use
> * @dpcd: A cached copy of the DPCD capabilities for this sink
> *
> - * Returns: %True if the sink supports MST, %false otherwise
> + * Returns: enum drm_dp_mst_mode to indicate MST mode capability
> */
> -bool drm_dp_read_mst_cap(struct drm_dp_aux *aux,
> - const u8 dpcd[DP_RECEIVER_CAP_SIZE])
> +enum drm_dp_mst_mode drm_dp_read_mst_cap(struct drm_dp_aux *aux,
> + const u8
> dpcd[DP_RECEIVER_CAP_SIZE])
> {
> u8 mstm_cap;
>
> if (dpcd[DP_DPCD_REV] < DP_DPCD_REV_12)
> - return false;
> + return DRM_DP_SST;
>
> if (drm_dp_dpcd_readb(aux, DP_MSTM_CAP, &mstm_cap) != 1)
> - return false;
> + return DRM_DP_SST;
> +
> + if (mstm_cap & DP_MST_CAP)
> + return DRM_DP_MST;
> +
> + if (mstm_cap & DP_SINGLE_STREAM_SIDEBAND_MSG)
> + return DRM_DP_SST_SIDEBAND_MSG;
Bit[1] of MSTM_CAP indicates sideband messaging is supported or not and nothing to do with MST/SST. So would it make more sense to have it as DRM_DP_SIDEBAND_MSG?
Thanks and Regards,
Arun R Murthy
--------------------
>
> - return mstm_cap & DP_MST_CAP;
> + return DRM_DP_SST;
> }
> EXPORT_SYMBOL(drm_dp_read_mst_cap);
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 5045c34a16be..a1c304f451bd 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -4014,7 +4014,7 @@ intel_dp_can_mst(struct intel_dp *intel_dp)
>
> 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_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) ==
> DRM_DP_MST;
> }
>
> static void
> @@ -4023,7 +4023,7 @@ 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);
> + 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", diff --git a/drivers/gpu/drm/nouveau/nouveau_dp.c
> b/drivers/gpu/drm/nouveau/nouveau_dp.c
> index 7de7707ec6a8..fb06ee17d9e5 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dp.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dp.c
> @@ -181,7 +181,7 @@ nouveau_dp_probe_dpcd(struct nouveau_connector
> *nv_connector,
> if (nouveau_mst) {
> mstm = outp->dp.mstm;
> if (mstm)
> - mstm->can_mst = drm_dp_read_mst_cap(aux, dpcd);
> + mstm->can_mst = drm_dp_read_mst_cap(aux, dpcd)
> == DRM_DP_MST;
> }
>
> if (nouveau_dp_has_sink_count(connector, outp)) { diff --git
> a/include/drm/display/drm_dp_mst_helper.h
> b/include/drm/display/drm_dp_mst_helper.h
> index 9b19d8bd520a..3c9e128c444a 100644
> --- a/include/drm/display/drm_dp_mst_helper.h
> +++ b/include/drm/display/drm_dp_mst_helper.h
> @@ -818,7 +818,28 @@ int drm_dp_mst_topology_mgr_init(struct
> drm_dp_mst_topology_mgr *mgr,
>
> void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr
> *mgr);
>
> -bool drm_dp_read_mst_cap(struct drm_dp_aux *aux, const u8
> dpcd[DP_RECEIVER_CAP_SIZE]);
> +/**
> + * enum drm_dp_mst_mode - sink's MST mode capability */ enum
> +drm_dp_mst_mode {
> + /**
> + * @DRM_DP_SST: The sink does not support MST nor single stream
> sideband
> + * messaging.
> + */
> + DRM_DP_SST,
> + /**
> + * @DRM_DP_MST: Sink supports MST, more than one stream and
> single
> + * stream sideband messaging.
> + */
> + DRM_DP_MST,
> + /**
> + * @DRM_DP_SST_SIDEBAND_MSG: Sink supports only one stream and
> single
> + * stream sideband messaging.
> + */
> + DRM_DP_SST_SIDEBAND_MSG,
> +};
> +
> +enum drm_dp_mst_mode drm_dp_read_mst_cap(struct drm_dp_aux *aux,
> const
> +u8 dpcd[DP_RECEIVER_CAP_SIZE]);
> int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr
> *mgr, bool mst_state);
>
> int drm_dp_mst_hpd_irq_handle_event(struct drm_dp_mst_topology_mgr
> *mgr,
> --
> 2.39.2
