Messages in this thread | | | Date | Mon, 27 Feb 2023 13:24:48 -0800 | Subject | Re: [RFC PATCH 1/2] drm/msm/dpu: add dsc helper functions | From | Abhinav Kumar <> |
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On 2/27/2023 11:25 AM, Dmitry Baryshkov wrote: > 27 февраля 2023 г. 19:59:35 GMT+02:00, Abhinav Kumar <quic_abhinavk@quicinc.com> пишет: >> >> >> On 2/27/2023 4:45 AM, Dmitry Baryshkov wrote: >>> On Mon, 27 Feb 2023 at 01:49, Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: >>>> >>>> >>>> >>>> On 2/26/2023 5:09 AM, Dmitry Baryshkov wrote: >>>>> On 26/02/2023 02:47, Abhinav Kumar wrote: >>>>>> Hi Dmitry >>>>>> >>>>>> On 2/25/2023 7:23 AM, Dmitry Baryshkov wrote: >>>>>>> On 25/02/2023 02:36, Abhinav Kumar wrote: >>>>>>>> >>>>>>>> >>>>>>>> On 2/24/2023 3:53 PM, Dmitry Baryshkov wrote: >>>>>>>>> On Sat, 25 Feb 2023 at 00:26, Abhinav Kumar >>>>>>>>> <quic_abhinavk@quicinc.com> wrote: >>>>>>>>>> On 2/24/2023 1:36 PM, Dmitry Baryshkov wrote: >>>>>>>>>>> 24 февраля 2023 г. 23:23:03 GMT+02:00, Abhinav Kumar >>>>>>>>>>> <quic_abhinavk@quicinc.com> пишет: >>>>>>>>>>>> On 2/24/2023 1:13 PM, Dmitry Baryshkov wrote: >>>>>>>>>>>>> On 24/02/2023 21:40, Kuogee Hsieh wrote: >>>>>>>>>>>>>> Add DSC helper functions based on DSC configuration profiles >>>>>>>>>>>>>> to produce >>>>>>>>>>>>>> DSC related runtime parameters through both table look up and >>>>>>>>>>>>>> runtime >>>>>>>>>>>>>> calculation to support DSC on DPU. >>>>>>>>>>>>>> >>>>>>>>>>>>>> There are 6 different DSC configuration profiles are supported >>>>>>>>>>>>>> currently. >>>>>>>>>>>>>> DSC configuration profiles are differiented by 5 keys, DSC >>>>>>>>>>>>>> version (V1.1), >>>>>>>>>>>>>> chroma (444/422/420), colorspace (RGB/YUV), bpc(8/10), >>>>>>>>>>>>>> bpp (6/7/7.5/8/9/10/12/15) and SCR (0/1). >>>>>>>>>>>>>> >>>>>>>>>>>>>> Only DSC version V1.1 added and V1.2 will be added later. >>>>>>>>>>>>> >>>>>>>>>>>>> These helpers should go to >>>>>>>>>>>>> drivers/gpu/drm/display/drm_dsc_helper.c >>>>>>>>>>>>> Also please check that they can be used for i915 or for amdgpu >>>>>>>>>>>>> (ideally for both of them). >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> No, it cannot. So each DSC encoder parameter is calculated based >>>>>>>>>>>> on the HW core which is being used. >>>>>>>>>>>> >>>>>>>>>>>> They all get packed to the same DSC structure which is the >>>>>>>>>>>> struct drm_dsc_config but the way the parameters are computed is >>>>>>>>>>>> specific to the HW. >>>>>>>>>>>> >>>>>>>>>>>> This DPU file helper still uses the drm_dsc_helper's >>>>>>>>>>>> drm_dsc_compute_rc_parameters() like all other vendors do but >>>>>>>>>>>> the parameters themselves are very HW specific and belong to >>>>>>>>>>>> each vendor's dir. >>>>>>>>>>>> >>>>>>>>>>>> This is not unique to MSM. >>>>>>>>>>>> >>>>>>>>>>>> Lets take a few other examples: >>>>>>>>>>>> >>>>>>>>>>>> AMD: >>>>>>>>>>>> https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/amd/display/dc/dml/dsc/rc_calc_fpu.c#L165 >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> i915: >>>>>>>>>>>> https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/i915/display/intel_vdsc.c#L379 >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> I checked several values here. Intel driver defines more bpc/bpp >>>>>>>>>>> combinations, but the ones which are defined in intel_vdsc and in >>>>>>>>>>> this patch seem to match. If there are major differences there, >>>>>>>>>>> please point me to the exact case. >>>>>>>>>>> >>>>>>>>>>> I remember that AMD driver might have different values. >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Some values in the rc_params table do match. But the >>>>>>>>>> rc_buf_thresh[] doesnt. >>>>>>>>> >>>>>>>>> Because later they do: >>>>>>>>> >>>>>>>>> vdsc_cfg->rc_buf_thresh[i] = rc_buf_thresh[i] >> 6; >>>>>>>>> >>>>>>>>>> >>>>>>>>>> https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/i915/display/intel_vdsc.c#L40 >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Vs >>>>>>>>>> >>>>>>>>>> +static u16 dpu_dsc_rc_buf_thresh[DSC_NUM_BUF_RANGES - 1] = { >>>>>>>>>> + 0x0e, 0x1c, 0x2a, 0x38, 0x46, 0x54, >>>>>>>>>> + 0x62, 0x69, 0x70, 0x77, 0x79, 0x7b, 0x7d, 0x7e >>>>>>>>>> +}; >>>>>>>>> >>>>>>>>> I'd prefer to have 896, 1792, etc. here, as those values come from the >>>>>>>>> standard. As it's done in the Intel driver. >>>>>>>>> >>>>>>>> >>>>>>>> Got it, thanks >>>>>>>> >>>>>>>>>> I dont know the AMD calculation very well to say that moving this >>>>>>>>>> to the >>>>>>>>>> helper is going to help. >>>>>>>>> >>>>>>>>> Those calculations correspond (more or less) at the first glance to >>>>>>>>> what intel does for their newer generations. I think that's not our >>>>>>>>> problem for now. >>>>>>>>> >>>>>>>> >>>>>>>> Well, we have to figure out if each value matches and if each of >>>>>>>> them come from the spec for us and i915 and from which section. So >>>>>>>> it is unfortunately our problem. >>>>>>> >>>>>>> Otherwise it will have to be handled by Marijn, me or anybody else >>>>>>> wanting to hack up the DSC code. Or by anybody adding DSC support to >>>>>>> the next platform and having to figure out the difference between >>>>>>> i915, msm and their platform. >>>>>>> >>>>>> >>>>>> Yes, I wonder why the same doubt didn't arise when the other vendors >>>>>> added their support both from other maintainers and others. >>>>>> >>>>>> Which makes me think that like I wrote in my previous response, these >>>>>> are "recommended" values in the spec but its not mandatory. >>>>> >>>>> I think, it is because there were no other drivers to compare. In other >>>>> words, for a first driver it is pretty logical to have everything >>>>> handled on its own. As soon as we start getting other implementations of >>>>> a feature, it becomes logical to think if the code can be generalized. >>>>> This is what we see we with the HDCP series or with the code being moved >>>>> to DP helpers. >>>>> >>>> >>>> We were not the second, MSM was/is the third to add support for DSC afer >>>> i915 and AMD. Thats what made me think why whoever was the second didnt >>>> end up generalizing. Was it just missed out or was it intentionally left >>>> in the vendor driver. >>> >>> I didn't count AMD here, since it calculates some of the params rather >>> than using the fixed ones from the model. >>> >>>> >>>>>> >>>>>> Moving this to the drm_dsc_helper is generalizing the tables and not >>>>>> giving room for the vendors to customize even if they want to (which >>>>>> the spec does allow). >>>>> >>>>> That depends on the API you select. For example, in >>>>> intel_dsc_compute_params() I see customization being applied to >>>>> rc_buf_thresh in 6bpp case. I'd leave that to the i915 driver. >>>>> >>>> >>>> Thanks for going through the i915 to figure out that the 6bpp is handled >>>> in a customized way. So what you are saying is let the helper first fill >>>> up the recommended values of the spec, whatever is changed from that let >>>> the vendor driver override that. >>>> >>>> Thats where the case-by-case handling comes. >>>> >>>> Why not we do this way? Like you mentioned lets move these tables to the >>>> drm_dsc_helper and let MSM driver first use those. >>>> >>>> Then in a separate patchset if i915 and AMD would like to move to that, >>>> let them handle it for their respective drivers instead of MSM going >>>> through whats customized for each calculation and doing it. >>>> >>>> I am hesitant to take up that effort. >>> >>> Writing a tool to convert model's rc_Nbpc_Mbpp_foo.cfg into C >>> languages structures used by Intel code took 15-20 minutes. Plugging >>> generated structures took another 5 minutes. I will send the patches >>> later today or tomorrow, as I find a time slot to clean them. Thank >>> you for spending more time on arguing than it took me to generate & >>> verify the data. >>> >> >> Great, we will wait for your patches. We didnt intend to spend time on this at this point. We always wanted to take it up in a separate series of moving the tables. > > Getting rid of msm_display_dsc_config and then making use of drm_dsc_compute_rc_parameters() was bad enough. So, let's get things done in a good way now, rather than at some random point later. >
Alright, we will wait for your change then :)
> >> >> You preferred not to wait. Upto you. >> >> So thanks for doing it. >> >>>> >>>> If the recommended values work for the vendor, they can clean it up and >>>> move to the drm_dsc_helper themselves and preserving their >>>> customizations rather than one vendor doing it for all of them. >>>> >>>>> In case the driver needs to perform customization of the params, nothing >>>>> stops it drop applying after filling all the RC params in the >>>>> drm_dsc_config struct via the generic helper. >>>>> >>>>> >>>>>> So if this has any merit and if you or Marijn would like to take it >>>>>> up, go for it. We would do the same thing as either of you would have >>>>>> to in terms of figuring out the difference between msm and the i915 code. >>>>>> >>>>>> This is not a generic API we are trying to put in a helper, these are >>>>>> hard-coded tables so there is a difference between looking at these Vs >>>>>> looking at some common code which can move to the core. >>>>>> >>>>>>>> >>>>>>>>>> >>>>>>>>>> Also, i think its too risky to change other drivers to use >>>>>>>>>> whatever math >>>>>>>>>> we put in the drm_dsc_helper to compute thr RC params because >>>>>>>>>> their code >>>>>>>>>> might be computing and using this tables differently. >>>>>>>>>> >>>>>>>>>> Its too much ownership for MSM developers to move this to >>>>>>>>>> drm_dsc_helper >>>>>>>>>> and own that as it might cause breakage of basic DSC even if some >>>>>>>>>> values >>>>>>>>>> are repeated. >>>>>>>>> >>>>>>>>> It's time to stop thinking about ownership and start thinking about >>>>>>>>> shared code. We already have two instances of DSC tables. I don't >>>>>>>>> think having a third instance, which is a subset of an existing >>>>>>>>> dataset, would be beneficial to anybody. >>>>>>>>> AMD has complicated code which supports half-bit bpp and calculates >>>>>>>>> some of the parameters. But sharing data with the i915 driver is >>>>>>>>> straightforward. >>>>>>>>> >>>>>>>> >>>>>>>> Sorry, but I would like to get an ack from i915 folks if this is going >>>>>>>> to be useful to them if we move this to helper because we have to >>>>>>>> look at every table. Not just one. >>>>>>> >>>>>>> Added i915 maintainers to the CC list for them to be able to answer. >>>>>>> >>>>>> >>>>>> Thanks, lets wait to hear from them about where finally these tables >>>>>> should go but thats can be taken up as a separate effort too. >>>>>> >>>>>>>> >>>>>>>> Also, this is just 1.1, we will add more tables for 1.2. So we will >>>>>>>> have to end up changing both 1.1 and 1.2 tables as they are >>>>>>>> different for QC. >>>>>>> >>>>>>> I haven't heard back from Kuogee about the possible causes of using >>>>>>> rc/qp values from 1.2 even for 1.1 panels. Maybe you can comment on >>>>>>> that? In other words, can we always stick to the values from 1.2 >>>>>>> standard? What will be the drawback? >>>>>>> >>>>>>> Otherwise, we'd have to have two different sets of values, like you >>>>>>> do in your vendor driver. >>>>>>> >>>>>> >>>>>> I have responded to this in the other email. >>>>>> >>>>>> All this being said, even if the rc tables move the drm_dsc_helper >>>>>> either now or later on, we will still need MSM specific calculations >>>>>> for many of the other encoder parameters (which are again either >>>>>> hard-coded or calculated). Please refer to the >>>>>> sde_dsc_populate_dsc_config() downstream. And yes, you will not find >>>>>> those in the DP spec directly. >>>>>> >>>>>> So we will still need a dsc helper for MSM calculations to be common >>>>>> for DSI / DP irrespective of where the tables go. >>>>>> >>>>>> So, lets finalize that first. >>>>> >>>>> I went on and trimmed sde_dsc_populate_dsc_config() to remove >>>>> duplication with the drm_dsc_compute_rc_parameters() (which we already >>>>> use for the MSM DSI DSC). >>>>> >>>>> Not much is left: >>>>> >>>>> dsc->first_line_bpg_offset set via the switch >>>>> >>>>> dsc->line_buf_depth = bpc + 1; >>>>> dsc->mux_word_size = bpc > 10 ? DSC_MUX_WORD_SIZE_12_BPC: >>>>> DSC_MUX_WORD_SIZE_8_10_BPC; >>>>> >>>>> if ((dsc->dsc_version_minor == 0x2) && (dsc->native_420)) >>>>> dsc->nsl_bpg_offset = (2048 * >>>>> (DIV_ROUND_UP(dsc->second_line_bpg_offset, >>>>> (dsc->slice_height - 1)))); >>>>> >>>>> dsc->initial_scale_value = 8 * dsc->rc_model_size / >>>>> (dsc->rc_model_size - dsc->initial_offset); >>>>> >>>>> >>>>> mux_word_size comes from the standard (must) >>>>> initial_scale_value calculation is recommended, but not required >>>>> nsl_bpg_offset follows the standard (must), also see below (*). >>>>> >>>>> first_line_bpg_offset calculation differs between three drivers. The >>>>> standard also provides a recommended formulas. I think we can leave it >>>>> as is for now. >>>>> >>>>> I think, that mux_word_size and nsl_bpg_offset calculation should be >>>>> moved to drm_dsc_compute_rc_parameters(), while leaving >>>>> initial_scale_value in place (in the driver code). >>>>> >>>>> * I think nsl_bpg_offset is slightly incorrectly calculated. Standard >>>>> demands that it is set to 'second_line_bpg_offset / (slice_height - 1), >>>>> rounded up to 16 fraction bits', while SDE driver code sets it to the >>>>> value rounded up to the next integer (having 16 fraction bits >>>>> representation). >>>>> >>>>> In my opinion correct calculation should be: >>>>> dsc->nsl_bpg_offset = DIV_ROUND_UP(2048 * dsc->second_line_bpg_offset, >>>>> (dsc->slice_height - 1)); >>>>> >>>>> Could you please check, which one is correct according to the standard? >>>>> >>>>> >>>> >>>> Sure, i will check about nsl_bpg_offset. But sorry if I was not more >>>> clear about this but sde_dsc_populate_dsc_config() is only one example >>>> which from your analysis can be moved to the drm_dsc_helper() but not >>>> the initial line calculation _dce_dsc_initial_line_calc(), >>>> _dce_dsc_ich_reset_override_needed() , _dce_dsc_setup_helper(). >>> >>> The initial_line is already calculated in dpu_encoder.c. As for the >>> _dce_dsc_ich_reset_override_needed(), I don't think we support partial >>> updates in the upstream driver. >>> >>>> >>>> All of these are again common between DSI and DP. >>>> >>>> So in addition to thinking about what can be moved to the drm_dsc_helper >>>> also think about what is specific to MSM but common to DSI and DP modules. >>>> >>>> That was the bigger picture I was trying to convey. >>> >> >> _dce_dsc_initial_line_calc which will get expanded with v1.2 gets added has much more than whats there in upstream today. >> >> Dumping everything in dpu_encoder is not the solution. Sorry. > > But it is still the DPU thing. So, no problems. >
I am not fully convinced. We will wait for your post, then see how the code looks.
>> >>> >>> >
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