[PATCH v9 16/18] drm/amd/display: Recalculate VCPI slots for new DSC connectors

[Mikita Lipski]

On 12/20/19 4:41 PM, Lyude Paul wrote:
> So I reviewed this already but realized I made a very silly mistake, comments
> down below:
> 
> On Fri, 2019-12-13 at 15:08 -0500, mikita.lipski at amd.com wrote:
>> From: Mikita Lipski <mikita.lipski at amd.com>
>>
>> [why]
>> Since for DSC MST connector's PBN is claculated differently
>> due to compression, we have to recalculate both PBN and
>> VCPI slots for that connector.
>>
>> [how]
>> The function iterates through all the active streams to
>> find, which have DSC enabled, then recalculates PBN for
>> it and calls drm_dp_helper_update_vcpi_slots_for_dsc to
>> update connector's VCPI slots.
>>
>> v2: - use drm_dp_mst_atomic_enable_dsc per port to
>> enable/disable DSC
>>
>> v3: - Iterate through connector states from the state passed
>>      - On each connector state get stream from dc_state,
>> instead CRTC state
>>
>> Reviewed-by: Lyude Paul <lyude at redhat.com>
>> Signed-off-by: Mikita Lipski <mikita.lipski at amd.com>
>> ---
>>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 76 +++++++++++++++++--
>>   1 file changed, 71 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> index 93a230d956ee..2ac3a2f0b452 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -4986,6 +4986,69 @@ const struct drm_encoder_helper_funcs
>> amdgpu_dm_encoder_helper_funcs = {
>>   	.atomic_check = dm_encoder_helper_atomic_check
>>   };
>>   
>> +static int dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
>> +					    struct dc_state *dc_state)
>> +{
>> +	struct dc_stream_state *stream = NULL;
>> +	struct drm_connector *connector;
>> +	struct drm_connector_state *new_con_state, *old_con_state;
>> +	struct amdgpu_dm_connector *aconnector;
>> +	struct dm_connector_state *dm_conn_state;
>> +	int i, j, clock, bpp;
>> +	int vcpi, pbn_div, pbn = 0;
>> +
>> +	for_each_oldnew_connector_in_state(state, connector, old_con_state,
>> new_con_state, i) {
>> +
>> +		aconnector = to_amdgpu_dm_connector(connector);
>> +
>> +		if (!aconnector->port)
>> +			continue;
>> +
>> +		if (!new_con_state || !new_con_state->crtc)
>> +			continue;
>> +
>> +		dm_conn_state = to_dm_connector_state(new_con_state);
>> +
>> +		for (j = 0; j < dc_state->stream_count; j++) {
>> +			stream = dc_state->streams[j];
>> +			if (!stream)
>> +				continue;
>> +
>> +			if ((struct amdgpu_dm_connector*)stream-
>>> dm_stream_context == aconnector)
>> +				break;
>> +
>> +			stream = NULL;
>> +		}
>> +
>> +		if (!stream)
>> +			continue;
>> +
>> +		if (stream->timing.flags.DSC != 1) {
>> +			drm_dp_mst_atomic_enable_dsc(state,
>> +						     aconnector->port,
>> +						     dm_conn_state->pbn,
>> +						     0,
>> +						     false);
>> +			continue;
>> +		}
>> +
>> +		pbn_div = dm_mst_get_pbn_divider(stream->link);
>> +		bpp = stream->timing.dsc_cfg.bits_per_pixel;
>> +		clock = stream->timing.pix_clk_100hz / 10;
>> +		pbn = drm_dp_calc_pbn_mode(clock, bpp, true);
>> +		vcpi = drm_dp_mst_atomic_enable_dsc(state,
>> +						    aconnector->port,
>> +						    pbn, pbn_div,
>> +						    true);
>> +		if (vcpi < 0)
>> +			return vcpi;
>> +
>> +		dm_conn_state->pbn = pbn;
>> +		dm_conn_state->vcpi_slots = vcpi;
>> +	}
>> +	return 0;
>> +}
>> +
>>   static void dm_drm_plane_reset(struct drm_plane *plane)
>>   {
>>   	struct dm_plane_state *amdgpu_state = NULL;
>> @@ -8022,11 +8085,6 @@ static int amdgpu_dm_atomic_check(struct drm_device
>> *dev,
>>   	if (ret)
>>   		goto fail;
>>   
>> -	/* Perform validation of MST topology in the state*/
>> -	ret = drm_dp_mst_atomic_check(state);
>> -	if (ret)
>> -		goto fail;
>> -
>>   	if (state->legacy_cursor_update) {
>>   		/*
>>   		 * This is a fast cursor update coming from the plane update
>> @@ -8098,6 +8156,10 @@ static int amdgpu_dm_atomic_check(struct drm_device
>> *dev,
>>   		if (!compute_mst_dsc_configs_for_state(state, dm_state-
>>> context))
>>   			goto fail;
>>   
>> +		ret = dm_update_mst_vcpi_slots_for_dsc(state, dm_state-
>>> context);
>> +		if (ret)
>> +			goto fail;
>> +
>>   		if (dc_validate_global_state(dc, dm_state->context, false) !=
>> DC_OK) {
>>   			ret = -EINVAL;
>>   			goto fail;
>> @@ -8126,6 +8188,10 @@ static int amdgpu_dm_atomic_check(struct drm_device
>> *dev,
>>   				dc_retain_state(old_dm_state->context);
>>   		}
>>   	}
>> +	/* Perform validation of MST topology in the state*/
>> +	ret = drm_dp_mst_atomic_check(state);
>> +	if (ret)
>> +		goto fail;
> 
> I realized that we actually should make it so that we actually expose a
> version of drm_dp_mst_atomic_check() which allows you to manually specify a
> drm_dp_mst_topology_state, because otherwise we're checking the bandwidth caps
> of _ALL_ enabled topologies which could cause us to fail just because another
> topology's new state doesn't meet the bandwidth requirements yet because we
> haven't readjusted it for the fair share compute algorithm.
> 
But wouldn't we want to fail the whole atomic check even if one of the 
topology states fails?
We call compute_mst_dsc_configs_for_state() function before 
drm_dp_mst_atomic_check(), and during it driver will attmpt different 
compression configurations untill drm_dp_mst_atomic_check() passes 
because we call drm_dp_mst_atomic_check() inside 
compute_mst_dsc_configs_for_state() every time configuration is readjusted.

> Also, I think we should probably differentiate in the atomic check functions
> between failing an atomic check for a topology state because it doesn't meet
> the bandwidth requirements we set, vs. a topology state failing atomic check
> for other reasons (temporary deadlock, too many payloads, etc.). So basically-
> we should return -ENOSPC when we fail because of a bandwidth (including VCPI
> slot allocation) issue.
> 

Thanks, I will update drm_dp_mst_atomic_check_bw_limit() to return 
appropriate error values on bw failure.

>>   
>>   	/* Store the overall update type for use later in atomic check. */
>>   	for_each_new_crtc_in_state (state, crtc, new_crtc_state, i) {

-- 
Thanks,
Mikita Lipski
Software Engineer, AMD
mikita.lipski at amd.com