[PATCH 6/8] drm/msm/dpu: use dpu_perf_cfg in DPU core_perf code

[Dmitry Baryshkov]

On 20/06/2023 13:55, Konrad Dybcio wrote:
> On 20.06.2023 02:08, Dmitry Baryshkov wrote:
>> Simplify dpu_core_perf code by using only dpu_perf_cfg instead of using
>> full-featured catalog data.
>>
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
>> ---
> Acked-by: Konrad Dybcio <konrad.dybcio at linaro.org>
>
> Check below.
>
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c | 52 ++++++++-----------
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.h |  8 +--
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c       |  2 +-
>>   3 files changed, 27 insertions(+), 35 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 773e641eab28..78a7e3ea27a4 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
>> @@ -19,11 +19,11 @@
>>
>>   /**
>>    * _dpu_core_perf_calc_bw() - to calculate BW per crtc
>> - * @kms:  pointer to the dpu_kms
>> + * @perf_cfg: performance configuration
>>    * @crtc: pointer to a crtc
>>    * Return: returns aggregated BW for all planes in crtc.
>>    */
>> -static u64 _dpu_core_perf_calc_bw(struct dpu_kms *kms,
>> +static u64 _dpu_core_perf_calc_bw(const struct dpu_perf_cfg *perf_cfg,
>>              struct drm_crtc *crtc)
>>   {
>>      struct drm_plane *plane;
>> @@ -39,7 +39,7 @@ static u64 _dpu_core_perf_calc_bw(struct dpu_kms *kms,
>>              crtc_plane_bw += pstate->plane_fetch_bw;
>>      }
>>
>> -    bw_factor = kms->catalog->perf->bw_inefficiency_factor;
>> +    bw_factor = perf_cfg->bw_inefficiency_factor;
> It's set to 120 for all SoCs.. and it sounds very much like some kind of a
> hack.
>
> The 105 on the other inefficiency factor is easy to spot:
>
> (1024/1000)^2 = 1.048576 =~= 1.05 = 105%
>
> It comes from a MiB-MB-MHz conversion that Qcom splattered all over
> downstream as due to ancient tragical design decisions in msmbus
> (which leak to the downstream interconnect a bit):

This doesn't describe, why msm8226 and msm8974 had qcom,mdss-clk-factor
of 5/4. And 8084 got 1.05 as usual. I can only suppose that MDSS 1.0
(8974 v1) and 1.1 (8226) had some internal inefficiency / issues.

Also, this 1.05 is a clock inefficiency, so it should not be related
to msm bus client code.

>
> The logic needs to get some input that corresponds to a clock rate
> of a bus clock (19.2, 200, 300 Mhz etc.) but the APIs expect a Kbps
> value. So at one point they invented a MHZ_TO_MBPS macro which did this
> conversion the other way around and probably had to account for it.
>
> I think they tried to make it make more sense, but it ended up being
> even more spaghetti :/
>
> Not yet sure how it's done on RPMh icc, but with SMD RPM, passing e.g.
>
> opp-peak-kBps = <(200 * 8 * 1000)>; # 200 MHz * 8-wide * KHz-to-MHz
>
> results in a "correct" end rate.
>
> Konrad
>>      if (bw_factor) {
>>              crtc_plane_bw *= bw_factor;
>>              do_div(crtc_plane_bw, 100);


--
With best wishes
Dmitry