[Intel-gfx] [Heads up to maintainers] Re: [PATCH v8 1/1] drm/drm_mst: Use Extended Base Receiver Capability DPCD space
Jani Nikula
jani.nikula at intel.com
Mon May 3 08:33:33 UTC 2021
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.
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
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