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Message-ID: <1086300a-2c8e-f897-a0d7-84d36276a6b6@quicinc.com>
Date:   Mon, 4 Dec 2023 08:37:11 -0800
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Subject: Re: [PATCH v1] drm/msm/dpu: improve DSC allocation
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
CC:     <dri-devel@lists.freedesktop.org>, <robdclark@gmail.com>,
        <sean@poorly.run>, <swboyd@chromium.org>, <dianders@chromium.org>,
        <vkoul@kernel.org>, <daniel@ffwll.ch>, <airlied@gmail.com>,
        <agross@kernel.org>, <andersson@kernel.org>,
        <quic_abhinavk@quicinc.com>, <quic_jesszhan@quicinc.com>,
        <quic_sbillaka@quicinc.com>, <marijn.suijten@somainline.org>,
        <freedreno@lists.freedesktop.org>, <linux-arm-msm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <1701289898-12235-1-git-send-email-quic_khsieh@quicinc.com>
 <CAA8EJpqX0AWmLMrNo23cfsnU5q0ySDUkb1XTGwaxGt0eTPkLpg@mail.gmail.com>
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From:   Kuogee Hsieh <quic_khsieh@quicinc.com>
In-Reply-To: <CAA8EJpqX0AWmLMrNo23cfsnU5q0ySDUkb1XTGwaxGt0eTPkLpg@mail.gmail.com>
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On 11/29/2023 7:57 PM, Dmitry Baryshkov wrote:
> On Wed, 29 Nov 2023 at 22:31, Kuogee Hsieh <quic_khsieh@quicinc.com> wrote:
>> A DCE (Display Compression Engine) contains two DSC hard slice encoders.
>> Each DCE start with even DSC encoder index followed by an odd DSC encoder
>> index. Each encoder can work independently. But Only two DSC encoders from
>> same DCE can be paired to work together to support merge mode. In addition,
>> the DSC with even index have to mapping to even pingpong index and DSC with
>> odd index have to mapping to odd pingpong index at its data path. This patch
>> improve DSC allocation mechanism with consideration of above factors.
> Is this applicable to old DSC 1.1 encoders?
yes, this algorithm should work with V1 too
>
>> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 94 +++++++++++++++++++++++++++++-----
>>   1 file changed, 82 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>> index f9215643..427d70d 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>> @@ -466,24 +466,94 @@ static int _dpu_rm_reserve_dsc(struct dpu_rm *rm,
>>                                 struct drm_encoder *enc,
>>                                 const struct msm_display_topology *top)
>>   {
>> -       int num_dsc = top->num_dsc;
>> -       int i;
>> +       int num_dsc = 0;
>> +       int i, pp_idx;
>> +       bool pair = false;
>> +       int dsc_idx[DSC_MAX - DSC_0];
>> +       uint32_t pp_to_enc_id[PINGPONG_MAX - PINGPONG_0];
>> +       int pp_max = PINGPONG_MAX - PINGPONG_0;
>> +
>> +       if (!top->num_dsc || !top->num_intf)
>> +               return 0;
>> +
>> +       /*
>> +        * Truth:
>> +        * 1) every layer mixer only connects to one pingpong
>> +        * 2) no pingpong split -- two layer mixers shared one pingpong
>> +        * 3) each DSC engine contains two dsc encoders
>> +        *    -- index(0,1), index (2,3),... etc
>> +        * 4) dsc pair can only happens with same DSC engine except 4 dsc
>> +        *    merge mode application (8k) which need two DSC engines
>> +        * 5) odd pingpong connect to odd dsc
>> +        * 6) even pingpong connect even dsc
>> +        */
>> +
>> +       /* num_dsc should be either 1, 2 or 4 */
>> +       if (top->num_dsc > top->num_intf)       /* merge mode */
>> +               pair = true;
>> +
>> +       /* fill working copy with pingpong list */
>> +       memcpy(pp_to_enc_id, global_state->pingpong_to_enc_id, sizeof(pp_to_enc_id));
>> +
>> +       for (i = 0; i < ARRAY_SIZE(rm->dsc_blks); i++) {
> && num_dsc < top->num_dsc
>
>> +               if (!rm->dsc_blks[i])   /* end of dsc list */
>> +                       break;
> I'd say, it's `continue' instead, let's just skip the index.
>
>> -       /* check if DSC required are allocated or not */
>> -       for (i = 0; i < num_dsc; i++) {
>> -               if (!rm->dsc_blks[i]) {
>> -                       DPU_ERROR("DSC %d does not exist\n", i);
>> -                       return -EIO;
>> +               if (global_state->dsc_to_enc_id[i]) {   /* used */
>> +                       /* consective dsc index to be paired */
>> +                       if (pair && num_dsc) {  /* already start pairing, re start */
>> +                               num_dsc = 0;
>> +                               /* fill working copy with pingpong list */
>> +                               memcpy(pp_to_enc_id, global_state->pingpong_to_enc_id,
>> +                                                               sizeof(pp_to_enc_id));
>> +                       }
>> +                       continue;
>>                  }
>>
>> -               if (global_state->dsc_to_enc_id[i]) {
>> -                       DPU_ERROR("DSC %d is already allocated\n", i);
>> -                       return -EIO;
>> +               /* odd index can not become start of pairing */
>> +               if (pair && (i & 0x01) && !num_dsc)
>> +                       continue;
> After looking at all conditions, can we have two different helpers?
> One which allocates a single DSC and another one which allocates a
> pair. For the pair you can skip odd indices at all and just check if
> DSC_i and DSC_i+1 are free.
>
>> +
>> +               /*
>> +                * find the pingpong index which had been reserved
>> +                * previously at layer mixer allocation
>> +                */
>> +               for (pp_idx = 0; pp_idx < pp_max; pp_idx++) {
>> +                       if (pp_to_enc_id[pp_idx] == enc->base.id)
>> +                               break;
>>                  }
>> +
>> +               /*
>> +                * dsc even index must map to pingpong even index
>> +                * dsc odd index must map to pingpong odd index
>> +                */
>> +               if ((i & 0x01) != (pp_idx & 0x01))
>> +                       continue;
>> +
>> +               /*
>> +                * delete pp_idx so that it can not be found at next search
>> +                * in the case of pairing
>> +                */
>> +               pp_to_enc_id[pp_idx] = NULL;
>> +
>> +               dsc_idx[num_dsc++] = i;
>> +               if (num_dsc >= top->num_dsc)
>> +                       break;
>>          }
>>
>> -       for (i = 0; i < num_dsc; i++)
>> -               global_state->dsc_to_enc_id[i] = enc->base.id;
>> +       if (num_dsc < top->num_dsc) {
>> +               DPU_ERROR("DSC allocation failed num_dsc=%d required=%d\n",
>> +                                               num_dsc, top->num_dsc );
>> +               return -ENAVAIL;
>> +       }
>> +
>> +       /* reserve dsc */
>> +       for (i = 0; i < top->num_dsc; i++) {
>> +               int j;
>> +
>> +               j = dsc_idx[i];
>> +               global_state->dsc_to_enc_id[j] = enc->base.id;
>> +       }
>>
>>          return 0;
>>   }
>> --
>> 2.7.4
>>
>