Re: [PATCH v2 06/16] drm/i915/mst: split out a helper for figuring out the TU

[Jani Nikula <jani.nikula@intel.com>]

On Tue, 31 Dec 2024, Imre Deak <imre.deak@intel.com> wrote:
> On Thu, Dec 19, 2024 at 11:33:55PM +0200, Jani Nikula wrote:
>> Extract intel_dp_mtp_tu_compute_config() for figuring out the TU. Move
>> the link configuration and mst state access to the callers. This will be
>> easier to adapt to 128b/132b SST.
>> 
>> v2: Don't add SST stuff here yet
>> 
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 53 ++++++++++++++-------
>>  drivers/gpu/drm/i915/display/intel_dp_mst.h |  7 +++
>>  2 files changed, 42 insertions(+), 18 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
>> index 51f0248084b6..d08824d2fefe 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
>> @@ -209,31 +209,23 @@ static int intel_dp_mst_dsc_get_slice_count(const struct intel_connector *connec
>>  					    num_joined_pipes);
>>  }
>>  
>> -static int mst_stream_find_vcpi_slots_for_bpp(struct intel_dp *intel_dp,
>> -					      struct intel_crtc_state *crtc_state,
>> -					      int max_bpp, int min_bpp,
>> -					      struct link_config_limits *limits,
>> -					      struct drm_connector_state *conn_state,
>> -					      int step, bool dsc)
>> +int intel_dp_mtp_tu_compute_config(struct intel_dp *intel_dp,
>> +				   struct intel_crtc_state *crtc_state,
>> +				   int max_bpp, int min_bpp,
>> +				   struct drm_connector_state *conn_state,
>> +				   int step, bool dsc)
>>  {
>>  	struct intel_display *display = to_intel_display(intel_dp);
>>  	struct drm_atomic_state *state = crtc_state->uapi.state;
>> -	struct drm_dp_mst_topology_state *mst_state;
>>  	struct intel_connector *connector =
>>  		to_intel_connector(conn_state->connector);
>>  	const struct drm_display_mode *adjusted_mode =
>>  		&crtc_state->hw.adjusted_mode;
>> +	fixed20_12 pbn_div;
>>  	int bpp, slots = -EINVAL;
>>  	int dsc_slice_count = 0;
>>  	int max_dpt_bpp;
>>  
>> -	mst_state = drm_atomic_get_mst_topology_state(state, &intel_dp->mst_mgr);
>> -	if (IS_ERR(mst_state))
>> -		return PTR_ERR(mst_state);
>> -
>> -	crtc_state->lane_count = limits->max_lane_count;
>> -	crtc_state->port_clock = limits->max_rate;
>> -
>>  	if (dsc) {
>>  		if (!intel_dp_supports_fec(intel_dp, connector, crtc_state))
>>  			return -EINVAL;
>> @@ -241,8 +233,8 @@ static int mst_stream_find_vcpi_slots_for_bpp(struct intel_dp *intel_dp,
>>  		crtc_state->fec_enable = !intel_dp_is_uhbr(crtc_state);
>>  	}
>>  
>> -	mst_state->pbn_div = drm_dp_get_vc_payload_bw(crtc_state->port_clock,
>> -						      crtc_state->lane_count);
>> +	pbn_div = drm_dp_get_vc_payload_bw(crtc_state->port_clock,
>> +					   crtc_state->lane_count);
>
> Nit: looking this up from drm_dp_mst_topology_state (once SST and MST is
> separated done only in the MST case) instead of recalculating the same
> would be better. Either way:

I don't disagree, but I couldn't figure out a neat way to deduplicate
that just yet. This seemed simpler. I think I'll leave that for future
improvement.

> Reviewed-by: Imre Deak <imre.deak@intel.com>

Thanks,
Jani.

>
>>  
>>  	max_dpt_bpp = intel_dp_mst_max_dpt_bpp(crtc_state, dsc);
>>  	if (max_bpp > max_dpt_bpp) {
>> @@ -302,7 +294,7 @@ static int mst_stream_find_vcpi_slots_for_bpp(struct intel_dp *intel_dp,
>>  		pbn.full = dfixed_const(intel_dp_mst_calc_pbn(adjusted_mode->crtc_clock,
>>  							      link_bpp_x16,
>>  							      remote_bw_overhead));
>> -		remote_tu = DIV_ROUND_UP(pbn.full, mst_state->pbn_div.full);
>> +		remote_tu = DIV_ROUND_UP(pbn.full, pbn_div.full);
>>  
>>  		/*
>>  		 * Aligning the TUs ensures that symbols consisting of multiple
>> @@ -320,7 +312,7 @@ static int mst_stream_find_vcpi_slots_for_bpp(struct intel_dp *intel_dp,
>>  		 * allocated for the whole path and the TUs allocated for the
>>  		 * first branch device's link also applies here.
>>  		 */
>> -		pbn.full = remote_tu * mst_state->pbn_div.full;
>> +		pbn.full = remote_tu * pbn_div.full;
>>  
>>  		drm_WARN_ON(display->drm, remote_tu < crtc_state->dp_m_n.tu);
>>  		crtc_state->dp_m_n.tu = remote_tu;
>> @@ -355,6 +347,31 @@ static int mst_stream_find_vcpi_slots_for_bpp(struct intel_dp *intel_dp,
>>  	return 0;
>>  }
>>  
>> +static int mst_stream_find_vcpi_slots_for_bpp(struct intel_dp *intel_dp,
>> +					      struct intel_crtc_state *crtc_state,
>> +					      int max_bpp, int min_bpp,
>> +					      struct link_config_limits *limits,
>> +					      struct drm_connector_state *conn_state,
>> +					      int step, bool dsc)
>> +{
>> +	struct drm_atomic_state *state = crtc_state->uapi.state;
>> +	struct drm_dp_mst_topology_state *mst_state;
>> +
>> +	mst_state = drm_atomic_get_mst_topology_state(state, &intel_dp->mst_mgr);
>> +	if (IS_ERR(mst_state))
>> +		return PTR_ERR(mst_state);
>> +
>> +	crtc_state->lane_count = limits->max_lane_count;
>> +	crtc_state->port_clock = limits->max_rate;
>> +
>> +	mst_state->pbn_div = drm_dp_get_vc_payload_bw(crtc_state->port_clock,
>> +						      crtc_state->lane_count);
>> +
>> +	return intel_dp_mtp_tu_compute_config(intel_dp, crtc_state,
>> +					      max_bpp, min_bpp,
>> +					      conn_state, step, dsc);
>> +}
>> +
>>  static int mst_stream_compute_link_config(struct intel_dp *intel_dp,
>>  					  struct intel_crtc_state *crtc_state,
>>  					  struct drm_connector_state *conn_state,
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.h b/drivers/gpu/drm/i915/display/intel_dp_mst.h
>> index 8343804ce3f8..c6bdc1d190a4 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.h
>> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.h
>> @@ -8,6 +8,7 @@
>>  
>>  #include <linux/types.h>
>>  
>> +struct drm_connector_state;
>>  struct intel_atomic_state;
>>  struct intel_crtc;
>>  struct intel_crtc_state;
>> @@ -30,4 +31,10 @@ bool intel_dp_mst_crtc_needs_modeset(struct intel_atomic_state *state,
>>  void intel_dp_mst_prepare_probe(struct intel_dp *intel_dp);
>>  bool intel_dp_mst_verify_dpcd_state(struct intel_dp *intel_dp);
>>  
>> +int intel_dp_mtp_tu_compute_config(struct intel_dp *intel_dp,
>> +				   struct intel_crtc_state *crtc_state,
>> +				   int max_bpp, int min_bpp,
>> +				   struct drm_connector_state *conn_state,
>> +				   int step, bool dsc);
>> +
>>  #endif /* __INTEL_DP_MST_H__ */
>> -- 
>> 2.39.5
>> 

-- 
Jani Nikula, Intel