linux-kernel - Re: [Freedreno] [REPOST PATCH v4 08/13] drm/msm/disp/dpu1: Don't use DSC with mode

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Date:   Fri, 18 Feb 2022 13:29:41 -0800
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Vinod Koul <vkoul@...nel.org>
CC:     Jonathan Marek <jonathan@...ek.ca>,
        David Airlie <airlied@...ux.ie>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Abhinav Kumar" <abhinavk@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Clark <robdclark@...il.com>,
        <dri-devel@...ts.freedesktop.org>, Daniel Vetter <daniel@...ll.ch>,
        <freedreno@...ts.freedesktop.org>
Subject: Re: [Freedreno] [REPOST PATCH v4 08/13] drm/msm/disp/dpu1: Don't use
 DSC with mode_3d



On 2/18/2022 1:21 PM, Dmitry Baryshkov wrote:
> On 18/02/2022 23:46, Abhinav Kumar wrote:
>>
>>
>> On 2/16/2022 11:12 PM, Dmitry Baryshkov wrote:
>>> On 17/02/2022 09:33, Abhinav Kumar wrote:
>>>>
>>>>
>>>> On 2/16/2022 10:10 PM, Vinod Koul wrote:
>>>>> On 16-02-22, 19:11, Abhinav Kumar wrote:
>>>>>>
>>>>>>
>>>>>> On 2/10/2022 2:34 AM, Vinod Koul wrote:
>>>>>>> We cannot enable mode_3d when we are using the DSC. So pass
>>>>>>> configuration to detect DSC is enabled and not enable mode_3d
>>>>>>> when we are using DSC
>>>>>>>
>>>>>>> We add a helper dpu_encoder_helper_get_dsc() to detect dsc
>>>>>>> enabled and pass this to .setup_intf_cfg()
>>>>>>>
>>>>>>> Signed-off-by: Vinod Koul <vkoul@...nel.org>
>>>>>>
>>>>>> We should not use 3D mux only when we use DSC merge topology.
>>>>>> I agree that today we use only 2-2-1 topology for DSC which means 
>>>>>> its using
>>>>>> DSC merge.
>>>>>>
>>>>>> But generalizing that 3D mux should not be used for DSC is not right.
>>>>>>
>>>>>> You can detect DSC merge by checking if there are two encoders and 
>>>>>> one
>>>>>> interface in the topology and if so, you can disable 3D mux.
>>>>>
>>>>> Right now with DSC we disable that as suggested by Dmitry last time.
>>>>> Whenever we introduce merge we should revisit this, for now this 
>>>>> should
>>>>> suffice
>>>>>
>>>>
>>>> Sorry I didnt follow.
>>>>
>>>> The topology which you are supporting today IS DSC merge 2-2-1. I 
>>>> didnt get what you mean by "whenever we introduce".
>>>>
>>>> I didnt follow Dmitry's comment either.
>>>>
>>>> "anybody adding support for SDE_RM_TOPOLOGY_DUALPIPE_3DMERGE_DSC 
>>>> handle this."
>>>>
>>>> 3D mux shouldnt be used when DSC merge is used.
>>>>
>>>> The topology Dmitry is referring to will not use DSC merge but you 
>>>> are using it here and thats why you had to make this patch in the 
>>>> first place. So I am not sure why would someone who uses 3D merge 
>>>> topology worry about DSC merge. Your patch is the one which deals 
>>>> with the topology in question.
>>>>
>>>> What I am suggesting is a small but necessary improvement to this 
>>>> patch.
>>>
>>> It seems that we can replace this patch by changing 
>>> dpu_encoder_helper_get_3d_blend_mode() to contain the following 
>>> condition (instead of the one present there). Does the following seem 
>>> correct to you:
>>>
>>> static inline enum dpu_3d_blend_mode 
>>> dpu_encoder_helper_get_3d_blend_mode(
>>>                  struct dpu_encoder_phys *phys_enc)
>>> {
>>>          struct dpu_crtc_state *dpu_cstate;
>>>
>>>          if (!phys_enc || phys_enc->enable_state == DPU_ENC_DISABLING)
>>>                  return BLEND_3D_NONE;
>>>
>>>          dpu_cstate = to_dpu_crtc_state(phys_enc->parent->crtc->state);
>>>
>>> +    /* Use merge_3d unless DSCMERGE topology is used */
>>>          if (phys_enc->split_role == ENC_ROLE_SOLO &&
>>> +           hweight(dpu_encoder_helper_get_dsc(phys_enc)) != 1 &&
> 
> Yes, the correct should be:
> hweight(...) == 2
> 
>>>              dpu_cstate->num_mixers == CRTC_DUAL_MIXERS)
>>>                  return BLEND_3D_H_ROW_INT;
>>>
>>>          return BLEND_3D_NONE;
>>> }
>>
>> This will not be enough. To detect whether DSC merge is enabled you 
>> need to query the topology. The above condition only checks if DSC is 
>> enabled not DSC merge.
>>
>> So the above function can be modified to use a helper like below 
>> instead of the hweight.
>>
>> bool dpu_encoder_get_dsc_merge_info(struct dpu_encoder_virt *dpu_enc)
>> {
>>      struct msm_display_topology topology = {0};
>>
>>      topology = dpu_encoder_get_topology(...);
>>
>>      if (topology.num_dsc > topology.num_intf)
> 
> num_intf is 1 or 2. If it's one, the split_role is SOLO
> hweight would return a num of bits in the DSC mask. It's 0, 1 or 2.
> So, if the split_role is SOLO and hweight is 2, we get exactly your 
> condition.
> 
num_intf is 1 in this case as only single interface is used. But even 4 
dsc encoders going to 2 interfaces its DSC merge. So assuming num_intf 
as 1 always is not right. Thats why I suggested a generalized confition 
like above.

> Does that sound correct?
> 
>>          return true;
>>      else
>>          return false;
>> }
>>
>> if (!dpu_encoder_get_dsc_merge_info() && other conditions listed above)
>>      return BLEND_3D_H_ROW_INT;
>> else
>>      BLEND_3D_NONE;
>>>
>>>
>>>>
>>>> All that you have to do is in query whether DSC merge is used from 
>>>> the topology. You can do it in multiple ways:
>>>>
>>>> 1) Either query this from the encoder
>>>> 2) Store a bool "dsc_merge" in the intf_cfg
>>>>
>>>
>>>
> 
>