Re: [PATCH v4 15/25] drm/msm/dpu: Add CWB to msm_display_topology

[Jessica Zhang <quic_jesszhan@quicinc.com>]

On 12/19/2024 9:03 PM, Dmitry Baryshkov wrote:
> On Mon, Dec 16, 2024 at 04:43:26PM -0800, Jessica Zhang wrote:
>> Add the cwb_enabled flag to msm_display topology and adjust the toplogy
>> to account for concurrent writeback
> 
> Why?

Hi Dmitry,

This flag is necessary to specify that CWB mux(es) need to be assigned 
for the given reqeusted topology.

> 
>>
>> Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 11 ++++++++++-
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c   | 10 ++++++++--
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h   |  2 ++
>>   3 files changed, 20 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> index b4bfded3d53025853cee112ca598533ece290318..b063c8fe4c0594772d84401fa56c9c21afc0ad18 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> @@ -1198,6 +1198,8 @@ static struct msm_display_topology dpu_crtc_get_topology(
>>   		dpu_encoder_update_topology(drm_enc, &topology, crtc_state->state,
>>   					    &crtc_state->adjusted_mode);
>>   
>> +	topology.cwb_enabled = drm_crtc_in_clone_mode(crtc_state);
>> +
>>   	/*
>>   	 * Datapath topology selection
>>   	 *
>> @@ -1209,9 +1211,16 @@ static struct msm_display_topology dpu_crtc_get_topology(
>>   	 * 2 LM, 1 INTF (stream merge to support high resolution interfaces)
>>   	 *
>>   	 * Add dspps to the reservation requirements if ctm is requested
>> +	 *
>> +	 * Only hardcode num_lm to 2 for cases where num_intf == 2 and CWB is not
>> +	 * enabled. This is because in cases where CWB is enabled, num_intf will
>> +	 * count both the WB and real-time phys encoders.
>> +	 *
>> +	 * For non-DSC CWB usecases, have the num_lm be decided by the
>> +	 * (mode->hdisplay > MAX_HDISPLAY_SPLIT) check.
>>   	 */
>>   
>> -	if (topology.num_intf == 2)
>> +	if (topology.num_intf == 2 && !topology.cwb_enabled)
>>   		topology.num_lm = 2;
>>   	else if (topology.num_dsc == 2)
>>   		topology.num_lm = 2;
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>> index b763ef19f4c60ae8a35df6a6ffb19e8411bc63f8..85adaf256b2c705d2d7df378b6ffc0e578f52bc3 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>> @@ -382,8 +382,14 @@ static int _dpu_rm_reserve_ctls(
>>   	int i = 0, j, num_ctls;
>>   	bool needs_split_display;
>>   
>> -	/* each hw_intf needs its own hw_ctrl to program its control path */
>> -	num_ctls = top->num_intf;
>> +	/*
>> +	 * For non-CWB mode, each hw_intf needs its own hw_ctl to program its
>> +	 * control path. Hardcode num_ctls to 1 if CWB is enabled
>> +	 */
> 
> Why?

This is because num_intf is based on the number of phys_encs. Since in 
the CWB case, the WB and real-time encoders will be driven by the same 
CTL. I can add this to the comment doc.

Thanks,

Jessica Zhang

> 
>> +	if (top->cwb_enabled)
>> +		num_ctls = 1;
>> +	else
>> +		num_ctls = top->num_intf;
>>   
>>   	needs_split_display = _dpu_rm_needs_split_display(top);
>>   
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
>> index b061dfdab52e04ab7d777e912a30173273cb3db7..12db21a2403ec6930894c36a58e898c5d94c2568 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
>> @@ -46,6 +46,7 @@ struct dpu_rm {
>>    * @num_dspp:     number of dspp blocks used
>>    * @num_dsc:      number of Display Stream Compression (DSC) blocks used
>>    * @needs_cdm:    indicates whether cdm block is needed for this display topology
>> + * @cwb_enabled:  indicates whether CWB is enabled for this display topology
>>    */
>>   struct msm_display_topology {
>>   	u32 num_lm;
>> @@ -53,6 +54,7 @@ struct msm_display_topology {
>>   	u32 num_dspp;
>>   	u32 num_dsc;
>>   	bool needs_cdm;
>> +	bool cwb_enabled;
>>   };
>>   
>>   int dpu_rm_init(struct drm_device *dev,
>>
>> -- 
>> 2.34.1
>>
> 
> -- 
> With best wishes
> Dmitry