[Heads up to maintainers] Re: [PATCH v8 1/1] drm/drm_mst: Use Extended Base Receiver Capability DPCD space
Daniel Vetter
daniel at ffwll.ch
Tue May 4 07:43:18 UTC 2021
On Mon, May 03, 2021 at 11:33:33AM +0300, Jani Nikula wrote:
> On Fri, 30 Apr 2021, Jani Nikula <jani.nikula at intel.com> wrote:
> > On Thu, 29 Apr 2021, Lyude Paul <lyude at redhat.com> wrote:
> >> JFYI Jani and Ben: I will be pushing this patch to drm-misc-next sometime
> >> today if there's no objections
> >
> > Thanks for the heads-up, I think this breaks i915. See my review
> > comments elsewhere in the thread.
>
> Looks like this was merged anyway.
Yeah in general rule of thumb is to let cross-driver stuff soak for a week
(assuming correctly cc'ed and all that already). I think that's the sweet
spot between maintainers who complain that it's too short and others
complaining it's too quick :-)
-Daniel
>
> 98025a62cb00 ("drm/dp_mst: Use Extended Base Receiver Capability DPCD space")
>
> I'm not happy how this played out.
>
> 1) You need to Cc relevant people
>
> 2) You need to get the ack before merging changes
>
> 3) You need to give people more than a day to react, with time zones and
> all; I replied as soon as I saw the heads-up, but it was already too
> late
>
> It's broken on i915, and perhaps that could be fixed.
>
> However I also think using DP spec rate codes and calling them "rate" is
> a bad interface, especially when the unit breaks down with DP 2.0 rate
> codes. It's confusing and it's not future proof. Fixing that afterwards
> falls to whoever comes next to pick up the pieces.
>
> I'd rather just see this reverted and redone.
>
>
> BR,
> Jani.
>
>
> >
> > BR,
> > Jani.
> >
> >
> >>
> >> On Wed, 2021-04-28 at 19:43 -0400, Nikola Cornij wrote:
> >>> [why]
> >>> DP 1.4a spec madates that if DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is
> >>> set, Extended Base Receiver Capability DPCD space must be used. Without
> >>> doing that, the three DPCD values that differ will be wrong, leading to
> >>> incorrect or limited functionality. MST link rate, for example, could
> >>> have a lower value. Also, Synaptics quirk wouldn't work out well when
> >>> Extended DPCD was not read, resulting in no DSC for such hubs.
> >>>
> >>> [how]
> >>> Modify MST topology manager to use the values from Extended DPCD where
> >>> applicable.
> >>>
> >>> To prevent regression on the sources that have a lower maximum link rate
> >>> capability than MAX_LINK_RATE from Extended DPCD, have the drivers
> >>> supply maximum lane count and rate at initialization time.
> >>>
> >>> This also reverts 'commit 2dcab875e763 ("Revert drm/dp_mst: Retrieve
> >>> extended DPCD caps for topology manager")', brining the change back to
> >>> the original 'commit ad44c03208e4 ("drm/dp_mst: Retrieve extended DPCD
> >>> caps for topology manager")'.
> >>>
> >>> Signed-off-by: Nikola Cornij <nikola.cornij at amd.com>
> >>> ---
> >>> .../display/amdgpu_dm/amdgpu_dm_mst_types.c | 5 +++
> >>> .../gpu/drm/amd/display/dc/core/dc_link_dp.c | 18 ++++++++++
> >>> drivers/gpu/drm/amd/display/dc/dc_link.h | 2 ++
> >>> drivers/gpu/drm/drm_dp_mst_topology.c | 33 ++++++++++++-------
> >>> drivers/gpu/drm/i915/display/intel_dp_mst.c | 6 +++-
> >>> drivers/gpu/drm/nouveau/dispnv50/disp.c | 3 +-
> >>> drivers/gpu/drm/radeon/radeon_dp_mst.c | 7 ++++
> >>> include/drm/drm_dp_mst_helper.h | 12 ++++++-
> >>> 8 files changed, 71 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 997567f6f0ba..b7e01b6fb328 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
> >>> @@ -429,6 +429,8 @@ void amdgpu_dm_initialize_dp_connector(struct
> >>> amdgpu_display_manager *dm,
> >>> struct amdgpu_dm_connector
> >>> *aconnector,
> >>> int link_index)
> >>> {
> >>> + struct dc_link_settings max_link_enc_cap = {0};
> >>> +
> >>> aconnector->dm_dp_aux.aux.name =
> >>> kasprintf(GFP_KERNEL, "AMDGPU DM aux hw bus %d",
> >>> link_index);
> >>> @@ -443,6 +445,7 @@ void amdgpu_dm_initialize_dp_connector(struct
> >>> amdgpu_display_manager *dm,
> >>> if (aconnector->base.connector_type == DRM_MODE_CONNECTOR_eDP)
> >>> return;
> >>>
> >>> + dc_link_dp_get_max_link_enc_cap(aconnector->dc_link,
> >>> &max_link_enc_cap);
> >>> aconnector->mst_mgr.cbs = &dm_mst_cbs;
> >>> drm_dp_mst_topology_mgr_init(
> >>> &aconnector->mst_mgr,
> >>> @@ -450,6 +453,8 @@ void amdgpu_dm_initialize_dp_connector(struct
> >>> amdgpu_display_manager *dm,
> >>> &aconnector->dm_dp_aux.aux,
> >>> 16,
> >>> 4,
> >>> + max_link_enc_cap.lane_count,
> >>> + max_link_enc_cap.link_rate,
> >>> aconnector->connector_id);
> >>>
> >>> drm_connector_attach_dp_subconnector_property(&aconnector->base);
> >>> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> >>> b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> >>> index 7d2e433c2275..6fe66b7ee53e 100644
> >>> --- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> >>> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> >>> @@ -1894,6 +1894,24 @@ bool dc_link_dp_sync_lt_end(struct dc_link *link,
> >>> bool link_down)
> >>> return true;
> >>> }
> >>>
> >>> +bool dc_link_dp_get_max_link_enc_cap(const struct dc_link *link, struct
> >>> dc_link_settings *max_link_enc_cap)
> >>> +{
> >>> + if (!max_link_enc_cap) {
> >>> + DC_LOG_ERROR("%s: Could not return max link encoder caps",
> >>> __func__);
> >>> + return false;
> >>> + }
> >>> +
> >>> + if (link->link_enc->funcs->get_max_link_cap) {
> >>> + link->link_enc->funcs->get_max_link_cap(link->link_enc,
> >>> max_link_enc_cap);
> >>> + return true;
> >>> + }
> >>> +
> >>> + DC_LOG_ERROR("%s: Max link encoder caps unknown", __func__);
> >>> + max_link_enc_cap->lane_count = 1;
> >>> + max_link_enc_cap->link_rate = 6;
> >>> + return false;
> >>> +}
> >>> +
> >>> static struct dc_link_settings get_max_link_cap(struct dc_link *link)
> >>> {
> >>> struct dc_link_settings max_link_cap = {0};
> >>> diff --git a/drivers/gpu/drm/amd/display/dc/dc_link.h
> >>> b/drivers/gpu/drm/amd/display/dc/dc_link.h
> >>> index b0013e674864..cb6d0543d839 100644
> >>> --- a/drivers/gpu/drm/amd/display/dc/dc_link.h
> >>> +++ b/drivers/gpu/drm/amd/display/dc/dc_link.h
> >>> @@ -346,6 +346,8 @@ bool dc_link_dp_set_test_pattern(
> >>> const unsigned char *p_custom_pattern,
> >>> unsigned int cust_pattern_size);
> >>>
> >>> +bool dc_link_dp_get_max_link_enc_cap(const struct dc_link *link, struct
> >>> dc_link_settings *max_link_enc_cap);
> >>> +
> >>> void dc_link_enable_hpd_filter(struct dc_link *link, bool enable);
> >>>
> >>> bool dc_link_is_dp_sink_present(struct dc_link *link);
> >>> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> >>> b/drivers/gpu/drm/drm_dp_mst_topology.c
> >>> index 5539a91b4031..31d9f3ff0d39 100644
> >>> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> >>> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> >>> @@ -3708,19 +3708,24 @@ int drm_dp_mst_topology_mgr_set_mst(struct
> >>> drm_dp_mst_topology_mgr *mgr, bool ms
> >>> /* set the device into MST mode */
> >>> if (mst_state) {
> >>> struct drm_dp_payload reset_pay;
> >>> + int lane_count;
> >>> + int link_rate;
> >>>
> >>> WARN_ON(mgr->mst_primary);
> >>>
> >>> /* get dpcd info */
> >>> - ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd,
> >>> DP_RECEIVER_CAP_SIZE);
> >>> - if (ret != DP_RECEIVER_CAP_SIZE) {
> >>> - drm_dbg_kms(mgr->dev, "failed to read DPCD\n");
> >>> + ret = drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd);
> >>> + if (ret < 0) {
> >>> + drm_dbg_kms(mgr->dev, "%s: failed to read DPCD, ret
> >>> %d\n",
> >>> + mgr->aux->name, ret);
> >>> goto out_unlock;
> >>> }
> >>>
> >>> + 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);
> >>> mgr->pbn_div = drm_dp_get_vc_payload_bw(mgr,
> >>> -
> >>> drm_dp_bw_code_to_link
> >>> _rate(mgr->dpcd[1]),
> >>> - mgr->dpcd[2] &
> >>> DP_MAX_LANE_COUNT_MASK);
> >>> + drm_dp_bw_code_to_li
> >>> nk_rate(link_rate),
> >>> + lane_count);
> >>> if (mgr->pbn_div == 0) {
> >>> ret = -EINVAL;
> >>> goto out_unlock;
> >>> @@ -5448,14 +5453,17 @@ EXPORT_SYMBOL(drm_atomic_get_mst_topology_state);
> >>> * @aux: DP helper aux channel to talk to this device
> >>> * @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
> >>> * @conn_base_id: the connector object ID the MST device is connected to.
> >>> *
> >>> * Return 0 for success, or negative error code on failure
> >>> */
> >>> 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, int conn_base_id)
> >>> + int max_dpcd_transaction_bytes, int
> >>> max_payloads,
> >>> + int max_lane_count, int max_link_rate,
> >>> + int conn_base_id)
> >>> {
> >>> struct drm_dp_mst_topology_state *mst_state;
> >>>
> >>> @@ -5490,6 +5498,8 @@ int drm_dp_mst_topology_mgr_init(struct
> >>> drm_dp_mst_topology_mgr *mgr,
> >>> mgr->aux = aux;
> >>> mgr->max_dpcd_transaction_bytes = max_dpcd_transaction_bytes;
> >>> mgr->max_payloads = max_payloads;
> >>> + mgr->max_lane_count = max_lane_count;
> >>> + mgr->max_link_rate = max_link_rate;
> >>> mgr->conn_base_id = conn_base_id;
> >>> if (max_payloads + 1 > sizeof(mgr->payload_mask) * 8 ||
> >>> max_payloads + 1 > sizeof(mgr->vcpi_mask) * 8)
> >>> @@ -5896,14 +5906,13 @@ struct drm_dp_aux
> >>> *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
> >>> if (drm_dp_has_quirk(&desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD)
> >>> &&
> >>> port->mgr->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14 &&
> >>> port->parent == port->mgr->mst_primary) {
> >>> - u8 downstreamport;
> >>> + u8 dpcd_ext[DP_RECEIVER_CAP_SIZE];
> >>>
> >>> - if (drm_dp_dpcd_read(&port->aux, DP_DOWNSTREAMPORT_PRESENT,
> >>> - &downstreamport, 1) < 0)
> >>> + if (drm_dp_read_dpcd_caps(port->mgr->aux, dpcd_ext) < 0)
> >>> return NULL;
> >>>
> >>> - if ((downstreamport & DP_DWN_STRM_PORT_PRESENT) &&
> >>> - ((downstreamport & DP_DWN_STRM_PORT_TYPE_MASK)
> >>> + if ((dpcd_ext[DP_DOWNSTREAMPORT_PRESENT] &
> >>> DP_DWN_STRM_PORT_PRESENT) &&
> >>> + ((dpcd_ext[DP_DOWNSTREAMPORT_PRESENT] &
> >>> DP_DWN_STRM_PORT_TYPE_MASK)
> >>> != DP_DWN_STRM_PORT_TYPE_ANALOG))
> >>> return port->mgr->aux;
> >>> }
> >>> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> >>> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> >>> index 860381d68d9d..a4245eb48ef4 100644
> >>> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> >>> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> >>> @@ -942,6 +942,7 @@ intel_dp_mst_encoder_init(struct intel_digital_port
> >>> *dig_port, int conn_base_id)
> >>> struct intel_dp *intel_dp = &dig_port->dp;
> >>> enum port port = dig_port->base.port;
> >>> int ret;
> >>> + int bios_max_link_rate;
> >>>
> >>> if (!HAS_DP_MST(i915) || intel_dp_is_edp(intel_dp))
> >>> return 0;
> >>> @@ -956,8 +957,11 @@ intel_dp_mst_encoder_init(struct intel_digital_port
> >>> *dig_port, int conn_base_id)
> >>>
> >>> /* create encoders */
> >>> intel_dp_create_fake_mst_encoders(dig_port);
> >>> + bios_max_link_rate = intel_bios_dp_max_link_rate(&dig_port->base);
> >>> ret = drm_dp_mst_topology_mgr_init(&intel_dp->mst_mgr, &i915->drm,
> >>> - &intel_dp->aux, 16, 3,
> >>> conn_base_id);
> >>> + &intel_dp->aux, 16, 3,
> >>> + dig_port->max_lanes,
> >>> + bios_max_link_rate / 27000,
> >>> 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 1c9c0cdf85db..e02f9d2d74eb 100644
> >>> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> >>> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> >>> @@ -1617,7 +1617,8 @@ 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,
> >>> - max_payloads, conn_base_id);
> >>> + max_payloads, outp->dcb-
> >>> >dpconf.link_nr,
> >>> + 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 59cf1d288465..8f0b2dccd199 100644
> >>> --- a/drivers/gpu/drm/radeon/radeon_dp_mst.c
> >>> +++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c
> >>> @@ -629,13 +629,20 @@ int
> >>> radeon_dp_mst_init(struct radeon_connector *radeon_connector)
> >>> {
> >>> struct drm_device *dev = radeon_connector->base.dev;
> >>> + int max_link_rate;
> >>>
> >>> if (!radeon_connector->ddc_bus->has_aux)
> >>> return 0;
> >>>
> >>> + if (radeon_connector_is_dp12_capable(&radeon_connector->base))
> >>> + max_link_rate = 0x14;
> >>> + else
> >>> + max_link_rate = 0x0a;
> >>> +
> >>> 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, 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 20dc705642bd..b5b0bf37813b 100644
> >>> --- a/include/drm/drm_dp_mst_helper.h
> >>> +++ b/include/drm/drm_dp_mst_helper.h
> >>> @@ -593,6 +593,14 @@ struct drm_dp_mst_topology_mgr {
> >>> * @max_payloads: maximum number of payloads the GPU can generate.
> >>> */
> >>> int max_payloads;
> >>> + /**
> >>> + * @max_lane_count: maximum number of lanes the GPU can drive.
> >>> + */
> >>> + int max_lane_count;
> >>> + /**
> >>> + * @max_link_rate: maximum link rate per lane GPU can output.
> >>> + */
> >>> + int max_link_rate;
> >>> /**
> >>> * @conn_base_id: DRM connector ID this mgr is connected to. Only
> >>> used
> >>> * to build the MST connector path value.
> >>> @@ -765,7 +773,9 @@ struct drm_dp_mst_topology_mgr {
> >>> 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, int conn_base_id);
> >>> + int max_payloads,
> >>> + 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);
> >>>
>
> --
> Jani Nikula, Intel Open Source Graphics Center
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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