Re: [PATCH v2 1/1] drm/dp_mst: Use kHz as link rate units when settig source max link caps at init

Lyude Paul
2021-05-13T16:30:37Z

Reviewed-by: Lyude Paul <lyude@redhat.com>

Will let this sit on the list for a few days to see if anyone's got any
objections and then I'll go ahead and push it

On Wed, 2021-05-12 at 17:00 -0400, Nikola Cornij wrote:
> [why]
> Link rate in kHz is what is eventually required to calculate the link
> bandwidth, which makes kHz a more generic unit. This should also make
> forward-compatibility with new DP standards easier.
>
> [how]
> - Replace 'link rate DPCD code' with 'link rate in kHz' when used with
> drm_dp_mst_topology_mgr_init()
> - Add/remove related DPCD code conversion from/to kHz where applicable
>
> Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
> Acked-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c   | 4 ++--
>  drivers/gpu/drm/drm_dp_mst_topology.c                     | 8 ++++----
>  drivers/gpu/drm/i915/display/intel_dp_mst.c               | 4 ++--
>  drivers/gpu/drm/nouveau/dispnv50/disp.c                   | 5 +++--
>  drivers/gpu/drm/radeon/radeon_dp_mst.c                    | 2 +-
>  include/drm/drm_dp_mst_helper.h                           | 8 ++++----
>  6 files changed, 16 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> index 4a0c24ce5f7d..f78dd021f591 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> @@ -458,8 +458,8 @@ void amdgpu_dm_initialize_dp_connector(struct
> amdgpu_display_manager *dm,
>                 &aconnector->dm_dp_aux.aux,
>                 16,
>                 4,
> -               (u8)max_link_enc_cap.lane_count,
> -               (u8)max_link_enc_cap.link_rate,
> +               max_link_enc_cap.lane_count,
> +               drm_dp_bw_code_to_link_rate(max_link_enc_cap.link_rate),
>                 aconnector->connector_id);
>
>         drm_connector_attach_dp_subconnector_property(&aconnector->base);
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 54604633e65c..32b7f8983b94 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -3722,9 +3722,9 @@ int drm_dp_mst_topology_mgr_set_mst(struct
> drm_dp_mst_topology_mgr *mgr, bool ms
>                 }
>
>                 lane_count = min_t(int, mgr->dpcd[2] & DP_MAX_LANE_COUNT_MASK,
> mgr->max_lane_count);
> -               link_rate = min_t(int, mgr->dpcd[1], mgr->max_link_rate);
> +               link_rate = min_t(int, drm_dp_bw_code_to_link_rate(mgr-
> >dpcd[1]), mgr->max_link_rate);
>                 mgr->pbn_div = drm_dp_get_vc_payload_bw(mgr,
> -
>                                                        drm_dp_bw_code_to_link_r
> ate(link_rate),
> +                                                       link_rate,
>                                                         lane_count);
>                 if (mgr->pbn_div == 0) {
>                         ret = -EINVAL;
> @@ -5454,7 +5454,7 @@ EXPORT_SYMBOL(drm_atomic_get_mst_topology_state);
>   * @max_dpcd_transaction_bytes: hw specific DPCD transaction limit
>   * @max_payloads: maximum number of payloads this GPU can source
>   * @max_lane_count: maximum number of lanes this GPU supports
> - * @max_link_rate: maximum link rate this GPU supports, units as in DPCD
> + * @max_link_rate: maximum link rate per lane this GPU supports in kHz
>   * @conn_base_id: the connector object ID the MST device is connected to.
>   *
>   * Return 0 for success, or negative error code on failure
> @@ -5462,7 +5462,7 @@ EXPORT_SYMBOL(drm_atomic_get_mst_topology_state);
>  int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
>                                  struct drm_device *dev, struct drm_dp_aux
> *aux,
>                                  int max_dpcd_transaction_bytes, int
> max_payloads,
> -                                u8 max_lane_count, u8 max_link_rate,
> +                                int max_lane_count, int max_link_rate,
>                                  int conn_base_id)
>  {
>         struct drm_dp_mst_topology_state *mst_state;
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index f608c0cb98f4..26f65445bc8a 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -960,8 +960,8 @@ intel_dp_mst_encoder_init(struct intel_digital_port
> *dig_port, int conn_base_id)
>         intel_dp_create_fake_mst_encoders(dig_port);
>         ret = drm_dp_mst_topology_mgr_init(&intel_dp->mst_mgr, &i915->drm,
>                                            &intel_dp->aux, 16, 3,
> -                                          (u8)dig_port->max_lanes,
> -
> drm_dp_link_rate_to_bw_code(max_source_rate),
> +                                          dig_port->max_lanes,
> +                                          max_source_rate,
>                                            conn_base_id);
>         if (ret)
>                 return ret;
> diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> index c46d0374b6e6..f949767698fc 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -1617,8 +1617,9 @@ nv50_mstm_new(struct nouveau_encoder *outp, struct
> drm_dp_aux *aux, int aux_max,
>         mstm->mgr.cbs = &nv50_mstm;
>
>         ret = drm_dp_mst_topology_mgr_init(&mstm->mgr, dev, aux, aux_max,
> -                                          (u8)max_payloads, outp->dcb-
> >dpconf.link_nr,
> -                                          (u8)outp->dcb->dpconf.link_bw,
> conn_base_id);
> +                                          max_payloads, outp->dcb-
> >dpconf.link_nr,
> +                                          drm_dp_bw_code_to_link_rate(outp-
> >dcb->dpconf.link_bw),
> +                                          conn_base_id);
>         if (ret)
>                 return ret;
>
> diff --git a/drivers/gpu/drm/radeon/radeon_dp_mst.c
> b/drivers/gpu/drm/radeon/radeon_dp_mst.c
> index 13072c2a6502..ec867fa880a4 100644
> --- a/drivers/gpu/drm/radeon/radeon_dp_mst.c
> +++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c
> @@ -642,7 +642,7 @@ radeon_dp_mst_init(struct radeon_connector
> *radeon_connector)
>         radeon_connector->mst_mgr.cbs = &mst_cbs;
>         return drm_dp_mst_topology_mgr_init(&radeon_connector->mst_mgr, dev,
>                                             &radeon_connector->ddc_bus->aux,
> 16, 6,
> -                                           4, (u8)max_link_rate,
> +                                           4,
> drm_dp_bw_code_to_link_rate(max_link_rate),
>                                             radeon_connector->base.base.id);
>  }
>
> diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
> index c87a829b6498..ddb9231d0309 100644
> --- a/include/drm/drm_dp_mst_helper.h
> +++ b/include/drm/drm_dp_mst_helper.h
> @@ -596,11 +596,11 @@ struct drm_dp_mst_topology_mgr {
>         /**
>          * @max_lane_count: maximum number of lanes the GPU can drive.
>          */
> -       u8 max_lane_count;
> +       int max_lane_count;
>         /**
> -        * @max_link_rate: maximum link rate per lane GPU can output.
> +        * @max_link_rate: maximum link rate per lane GPU can output, in kHz.
>          */
> -       u8 max_link_rate;
> +       int max_link_rate;
>         /**
>          * @conn_base_id: DRM connector ID this mgr is connected to. Only used
>          * to build the MST connector path value.
> @@ -774,7 +774,7 @@ int drm_dp_mst_topology_mgr_init(struct
> drm_dp_mst_topology_mgr *mgr,
>                                  struct drm_device *dev, struct drm_dp_aux
> *aux,
>                                  int max_dpcd_transaction_bytes,
>                                  int max_payloads,
> -                                u8 max_lane_count, u8 max_link_rate,
> +                                int max_lane_count, int max_link_rate,
>                                  int conn_base_id);
>
>  void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr);

--
Sincerely,
Lyude Paul (she/her)
Software Engineer at Red Hat

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