[PATCH v4 4/9] drm/msm/dpu: make fix_core_ab_vote consistent with fix_core_ib_vote

[Abhinav Kumar]

On 1/9/2025 6:02 PM, Dmitry Baryshkov wrote:
> On Thu, Jan 09, 2025 at 05:40:23PM -0800, Abhinav Kumar wrote:
>>
>>
>> On 1/5/2025 7:07 PM, Dmitry Baryshkov wrote:
>>> The fix_core_ab_vote is an average bandwidth value, used for bandwidth
>>> overrides in several cases. However there is an internal inconsistency:
>>> fix_core_ib_vote is defined in KBps, while fix_core_ab_vote is defined
>>> in Bps.
>>>
>>> Fix that by changing the type of the variable to u32 and using * 1000ULL
>>> multiplier when setting up the dpu_core_perf_params::bw_ctl value.
>>>
>>
>> Actually after looking at this, I have another question.
>>
>> How did you conclude that fix_core_ib_vote is in KBps?
>>
>> min_dram_ib is in KBps in the catalog but how is fix_core_ib_vote?
>>
>> It depends on the interpretation perhaps. If the debugfs was supposed to
>> operate under the expectation that the provided value will be pre-multiplied
>> by 1000 and given then that explains why it was not multiplied again.
>>
>> And I cross-checked some of the internal usages of the debugfs, the values
>> provided to it were in Bps and not KBps.
> 
> Well... As you wrote min_dram_ib is in KBps. So, by comparing the next
> two lines, fix_core_ib_vote should also be in kBps, as there is no
> premultiplier:
> 
>                  perf->max_per_pipe_ib = core_perf->fix_core_ib_vote;
> [...]
>                  perf->max_per_pipe_ib = perf_cfg->min_dram_ib;
> 
> And then, as a proof, perf->max_per_pipe_ib is passed to icc_set_bw()
> without any modifications:
> 
>                  icc_set_bw(kms->path[i], avg_bw, perf.max_per_pipe_ib);
> 

Understood max_per_pipe_ib. But then by the same logic, fix_core_ab_vote 
is always in Bps and not in KBps because bw_ctl is in Bps.

Is it really a discrepancy that fix_core_ib_vote is defined in KBps, 
while fix_core_ab_vote is defined in Bps because they are just following 
the units in which bw_ctl and max_per_pipe_ib were defined in resp.

> 
>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
>>> ---
>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c | 4 ++--
>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.h | 2 +-
>>>    2 files changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
>>> index 7263ab63a692554cd51a7fd91bd6250330179240..7cabc8f26908cfd2dbbffebd7c70fc37d9159733 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
>>> @@ -125,7 +125,7 @@ static void _dpu_core_perf_calc_crtc(const struct dpu_core_perf *core_perf,
>>>    		perf->max_per_pipe_ib = 0;
>>>    		perf->core_clk_rate = 0;
>>>    	} else if (core_perf->perf_tune.mode == DPU_PERF_MODE_FIXED) {
>>> -		perf->bw_ctl = core_perf->fix_core_ab_vote;
>>> +		perf->bw_ctl = core_perf->fix_core_ab_vote * 1000ULL;
>>>    		perf->max_per_pipe_ib = core_perf->fix_core_ib_vote;
>>>    		perf->core_clk_rate = core_perf->fix_core_clk_rate;
>>>    	} else {
>>> @@ -479,7 +479,7 @@ int dpu_core_perf_debugfs_init(struct dpu_kms *dpu_kms, struct dentry *parent)
>>>    			&perf->fix_core_clk_rate);
>>>    	debugfs_create_u32("fix_core_ib_vote", 0600, entry,
>>>    			&perf->fix_core_ib_vote);
>>> -	debugfs_create_u64("fix_core_ab_vote", 0600, entry,
>>> +	debugfs_create_u32("fix_core_ab_vote", 0600, entry,
>>>    			&perf->fix_core_ab_vote);
>>>    	return 0;
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.h
>>> index ca4595b4ec217697849af02446b23ed0857a0295..5e07119c14c6a9ed3413d0eaddbd93df5cc3f79d 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.h
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.h
>>> @@ -51,7 +51,7 @@ struct dpu_core_perf {
>>>    	u32 enable_bw_release;
>>>    	u64 fix_core_clk_rate;
>>>    	u32 fix_core_ib_vote;
>>> -	u64 fix_core_ab_vote;
>>> +	u32 fix_core_ab_vote;
>>>    };
>>>    int dpu_core_perf_crtc_check(struct drm_crtc *crtc,
>>>
>