Re: [PATCH 02/16] drm/i915/display: Prepare for dsc 3 stream splitter

["Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com>]

On 10/22/2024 1:21 PM, Jani Nikula wrote:
> On Tue, 22 Oct 2024, "Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com> wrote:
>> On 10/21/2024 6:16 PM, Jani Nikula wrote:
>>> On Mon, 21 Oct 2024, Ankit Nautiyal <ankit.k.nautiyal@intel.com> wrote:
>>>> At the moment dsc_split represents that dsc splitter is used or not.
>>>> With 3 DSC engines, the splitter can split into two streams or three
>>>> streams. Make the member dsc_split as int and set that to 2 when dsc
>>>> splitter splits to 2 stream.
>>> Maybe also name it accordingly? "dsc split" sounds like a boolean, not
>>> like an int.
>>>
>>> Moreover, when you change the meaning of a member, it's often good code
>>> hygiene to rename the member to catch any incorrect uses and to ensure
>>> you changed them all.
>> Noted. Will change the name accordingly.
>>
>>>> v2: Avoid new enum for dsc split. (Suraj)
>>>>
>>>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>>>> ---
>>>>    drivers/gpu/drm/i915/display/icl_dsi.c        |  2 +-
>>>>    drivers/gpu/drm/i915/display/intel_display.c  |  2 +-
>>>>    .../drm/i915/display/intel_display_types.h    |  2 +-
>>>>    drivers/gpu/drm/i915/display/intel_dp.c       |  2 +-
>>>>    drivers/gpu/drm/i915/display/intel_vdsc.c     | 20 ++++++++++++++-----
>>>>    5 files changed, 19 insertions(+), 9 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/display/icl_dsi.c b/drivers/gpu/drm/i915/display/icl_dsi.c
>>>> index 87a27d91d15d..553e75cf118c 100644
>>>> --- a/drivers/gpu/drm/i915/display/icl_dsi.c
>>>> +++ b/drivers/gpu/drm/i915/display/icl_dsi.c
>>>> @@ -1595,7 +1595,7 @@ static int gen11_dsi_dsc_compute_config(struct intel_encoder *encoder,
>>>>    
>>>>    	/* FIXME: split only when necessary */
>>>>    	if (crtc_state->dsc.slice_count > 1)
>>>> -		crtc_state->dsc.dsc_split = true;
>>>> +		crtc_state->dsc.dsc_split = 2;
>>>>    
>>>>    	/* FIXME: initialize from VBT */
>>>>    	vdsc_cfg->rc_model_size = DSC_RC_MODEL_SIZE_CONST;
>>>> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
>>>> index ef1436146325..9e2f0fd0558f 100644
>>>> --- a/drivers/gpu/drm/i915/display/intel_display.c
>>>> +++ b/drivers/gpu/drm/i915/display/intel_display.c
>>>> @@ -5741,7 +5741,7 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
>>>>    	PIPE_CONF_CHECK_I(dsc.config.nsl_bpg_offset);
>>>>    
>>>>    	PIPE_CONF_CHECK_BOOL(dsc.compression_enable);
>>>> -	PIPE_CONF_CHECK_BOOL(dsc.dsc_split);
>>>> +	PIPE_CONF_CHECK_I(dsc.dsc_split);
>>>>    	PIPE_CONF_CHECK_I(dsc.compressed_bpp_x16);
>>>>    
>>>>    	PIPE_CONF_CHECK_BOOL(splitter.enable);
>>>> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
>>>> index 2bb1fa64da2f..58f510909f4d 100644
>>>> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
>>>> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
>>>> @@ -1235,7 +1235,7 @@ struct intel_crtc_state {
>>>>    	/* Display Stream compression state */
>>>>    	struct {
>>>>    		bool compression_enable;
>>>> -		bool dsc_split;
>>>> +		int dsc_split;
>>>>    		/* Compressed Bpp in U6.4 format (first 4 bits for fractional part) */
>>>>    		u16 compressed_bpp_x16;
>>>>    		u8 slice_count;
>>>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>>>> index 286b272aa98c..c1867c883b73 100644
>>>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>>>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>>>> @@ -2409,7 +2409,7 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
>>>>    	 * then we need to use 2 VDSC instances.
>>>>    	 */
>>>>    	if (pipe_config->joiner_pipes || pipe_config->dsc.slice_count > 1)
>>>> -		pipe_config->dsc.dsc_split = true;
>>>> +		pipe_config->dsc.dsc_split = 2;
>>>>    
>>>>    	ret = intel_dp_dsc_compute_params(connector, pipe_config);
>>>>    	if (ret < 0) {
>>>> diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.c b/drivers/gpu/drm/i915/display/intel_vdsc.c
>>>> index 40525f5c4c42..3bce13c21756 100644
>>>> --- a/drivers/gpu/drm/i915/display/intel_vdsc.c
>>>> +++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
>>>> @@ -379,7 +379,14 @@ intel_dsc_power_domain(struct intel_crtc *crtc, enum transcoder cpu_transcoder)
>>>>    
>>>>    static int intel_dsc_get_vdsc_per_pipe(const struct intel_crtc_state *crtc_state)
>>>>    {
>>>> -	return crtc_state->dsc.dsc_split ? 2 : 1;
>>>> +	switch (crtc_state->dsc.dsc_split) {
>>>> +	case 2:
>>>> +		return 2;
>>>> +	case 0:
>>>> +	default:
>>>> +		break;
>>>> +	}
>>>> +	return 1;
>>> Seems overly complicated.
>>>
>>>>    }
>>>>    
>>>>    int intel_dsc_get_num_vdsc_instances(const struct intel_crtc_state *crtc_state)
>>>> @@ -976,8 +983,11 @@ void intel_dsc_get_config(struct intel_crtc_state *crtc_state)
>>>>    	if (!crtc_state->dsc.compression_enable)
>>>>    		goto out;
>>>>    
>>>> -	crtc_state->dsc.dsc_split = (dss_ctl2 & RIGHT_BRANCH_VDSC_ENABLE) &&
>>>> -		(dss_ctl1 & JOINER_ENABLE);
>>>> +	if ((dss_ctl1 & JOINER_ENABLE) &&
>>>> +	    (dss_ctl2 & RIGHT_BRANCH_VDSC_ENABLE))
>>> The extra parens are unnecessary.
>>>
>>>> +		crtc_state->dsc.dsc_split = 2;
>>>> +	else
>>>> +		crtc_state->dsc.dsc_split = 0;
>>>>    
>>>>    	intel_dsc_get_pps_config(crtc_state);
>>>>    out:
>>>> @@ -988,10 +998,10 @@ static void intel_vdsc_dump_state(struct drm_printer *p, int indent,
>>>>    				  const struct intel_crtc_state *crtc_state)
>>>>    {
>>>>    	drm_printf_indent(p, indent,
>>>> -			  "dsc-dss: compressed-bpp:" FXP_Q4_FMT ", slice-count: %d, split: %s\n",
>>>> +			  "dsc-dss: compressed-bpp:" FXP_Q4_FMT ", slice-count: %d, split: %d\n",
>>> So what does the reader think when they see "split: 1" in the logs?
>>> Split enabled?
>> I was meaning to capture the DSC split state as originally intended, and
>> extend it to have splitting to 3, 2, or None.
>>
>> With that we can never have split: 1, but can have either 3, 2, or 0.
>>
>> I realize, split:0 is a bit ambiguous, so I am thinking about:
>>
>> -change the dsc_split to dsc_streams: to capture number of DSC streams
>> per pipe, instead of DSC splitter operation.
>>
>> -dsc_streams can be 1, 2 and extended to 3.
>>
>> -Splitter state will then be implicit, 1 DSC Stream => No Splitter, 2
>> DSC Streams => Splitter used to split 2 DSC streams and so on.
>>
>> With that, deriving number of DSC engine will also be straight forward
>> (avoiding the switch case above).
> Maybe be even more explicit, and call it num_streams or stream_count or
> something like that.
>
> Also, the crtc_state->dsc.dsc_something is a tautology, the dsc_ prefix
> is unnecessary when it's already in a dsc substruct.

I agree, I am working with dsc.num_streams, something like : 
https://patchwork.freedesktop.org/patch/620816/?series=134992&rev=6

Regards,

Ankit


>
> BR,
> Jani.
>
>>
>> Thanks & Regards,
>>
>> Ankit
>>
>>
>>
>>>>    			  FXP_Q4_ARGS(crtc_state->dsc.compressed_bpp_x16),
>>>>    			  crtc_state->dsc.slice_count,
>>>> -			  str_yes_no(crtc_state->dsc.dsc_split));
>>>> +			  crtc_state->dsc.dsc_split);
>>>>    }
>>>>    
>>>>    void intel_vdsc_state_dump(struct drm_printer *p, int indent,