Re: [PATCH] media: iris: optimize COMV buffer allocation for VPU3x and VPU4x

[Vishnu Reddy <busanna.reddy@oss.qualcomm.com>]

On 4/21/2026 2:31 PM, Bryan O'Donoghue wrote:
> On 21/04/2026 07:41, Vishnu Reddy wrote:
>> The existing iris_vpu_dec_comv_size() used VIDEO_MAX_FRAME (32) as
>> num_comv count unconditionally when calculating the COMV buffer size.
>> This resulted in an oversized COMV buffer allocation throughout decode
>> session, wasting memory regardless of actual number of buffers required.
>
> You should define what a COMV buffer is before talking about how you are
> changing it, i.e. define the term Co-located Motion Vector (CMOV) and then use
> the abbreviation CMOV liberally as you wish.

Ack, will update accordingly.

>
>> For VPU3x and VPU4x platforms, introduce iris_vpu3x_4x_dec_comv_size() to
>> replace iris_vpu_dec_comv_size(). It derives num_comv dynamically, it
>
> "These derive num_cmove dynamically"

Ack.

>
>> uses inst->fw_min_count once the firmware has reported its minimum buffer
>> requirements, and fallback to inst->buffers[BUF_OUTPUT].min_count during
>> initialization before firmware has communicated its requirements. This
>> aligns the COMV buffer size to the actual count needed rather than always
>> allocating with fixed VIDEO_MAX_FRAME value.
>>
>> Additionally, during iris_vdec_inst_init(), fw_min_count was initialized
>> to MIN_BUFFERS instead of 0. This masked the fallback logic and caused the
>> COMV size calculation to use MIN_BUFFERS even before firmware had reported
>> its actual requirements. Fix this by initializing fw_min_count to 0.
>>
>> During testing of 1080p AVC, it reduces the COMV buffer size from 32.89MB
>> to 6.16MB per decode session, significantly reducing memory consumption.
>
> Cool nice fix.
>

Thanks!

>>
>> Signed-off-by: Vishnu Reddy <busanna.reddy@oss.qualcomm.com>
>> ---
>>   drivers/media/platform/qcom/iris/iris_vdec.c       |  2 +-
>>   drivers/media/platform/qcom/iris/iris_vpu_buffer.c | 24 +++++++++++++++++++---
>>   drivers/media/platform/qcom/iris/iris_vpu_buffer.h |  1 +
>>   3 files changed, 23 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/platform/qcom/iris/iris_vdec.c
>> b/drivers/media/platform/qcom/iris/iris_vdec.c
>> index 719217399a30..f433065e08b2 100644
>> --- a/drivers/media/platform/qcom/iris/iris_vdec.c
>> +++ b/drivers/media/platform/qcom/iris/iris_vdec.c
>> @@ -24,7 +24,7 @@ int iris_vdec_inst_init(struct iris_inst *inst)
>>       inst->fmt_src = kzalloc_obj(*inst->fmt_src);
>>       inst->fmt_dst = kzalloc_obj(*inst->fmt_dst);
>>
>> -    inst->fw_min_count = MIN_BUFFERS;
>> +    inst->fw_min_count = 0;
>>
>>       f = inst->fmt_src;
>>       f->type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
>> diff --git a/drivers/media/platform/qcom/iris/iris_vpu_buffer.c
>> b/drivers/media/platform/qcom/iris/iris_vpu_buffer.c
>> index 9270422c1601..57237543b229 100644
>> --- a/drivers/media/platform/qcom/iris/iris_vpu_buffer.c
>> +++ b/drivers/media/platform/qcom/iris/iris_vpu_buffer.c
>> @@ -731,6 +731,23 @@ static u32 iris_vpu_dec_comv_size(struct iris_inst *inst)
>>       u32 height = f->fmt.pix_mp.height;
>>       u32 width = f->fmt.pix_mp.width;
>>
>> +    if (inst->codec == V4L2_PIX_FMT_H264)
>> +        return hfi_buffer_comv_h264d(width, height, num_comv);
>> +    else if (inst->codec == V4L2_PIX_FMT_HEVC)
>> +        return hfi_buffer_comv_h265d(width, height, num_comv);
>> +
>> +    return 0;
>> +}
>> +
>> +static u32 iris_vpu3x_4x_dec_comv_size(struct iris_inst *inst)
>> +{
>> +    struct v4l2_format *f = inst->fmt_src;
>> +    u32 height = f->fmt.pix_mp.height;
>> +    u32 width = f->fmt.pix_mp.width;
>> +    u32 num_comv;
>> +
>> +    num_comv = inst->fw_min_count ? inst->fw_min_count :
>> inst->buffers[BUF_OUTPUT].min_count;
>
> Please just if/else this though its far easier to read/understand that way.
>

Ack.

Thank you
Vishnu Reddy
>> +
>>       if (inst->codec == V4L2_PIX_FMT_H264)
>>           return hfi_buffer_comv_h264d(width, height, num_comv);
>>       else if (inst->codec == V4L2_PIX_FMT_HEVC)
>> @@ -739,7 +756,8 @@ static u32 iris_vpu_dec_comv_size(struct iris_inst *inst)
>>           if (inst->fw_caps[DRAP].value)
>>               return 0;
>>           else
>> -            return hfi_buffer_comv_av1d(width, height, num_comv);
>> +            return hfi_buffer_comv_av1d(width, height,
>> +                            num_comv + AV1D_COMV_BUFFER_OVERHEAD);
>>       }
>>
>>       return 0;
>> @@ -2025,7 +2043,7 @@ u32 iris_vpu_buf_size(struct iris_inst *inst, enum
>> iris_buffer_type buffer_type)
>>
>>       static const struct iris_vpu_buf_type_handle
>> dec_internal_buf_type_handle[] = {
>>           {BUF_BIN,         iris_vpu_dec_bin_size             },
>> -        {BUF_COMV,        iris_vpu_dec_comv_size            },
>> +        {BUF_COMV,        iris_vpu3x_4x_dec_comv_size       },
>>           {BUF_NON_COMV,    iris_vpu_dec_non_comv_size        },
>>           {BUF_LINE,        iris_vpu_dec_line_size            },
>>           {BUF_PERSIST,     iris_vpu_dec_persist_size         },
>> @@ -2098,7 +2116,7 @@ u32 iris_vpu4x_buf_size(struct iris_inst *inst, enum
>> iris_buffer_type buffer_typ
>>
>>       static const struct iris_vpu_buf_type_handle
>> dec_internal_buf_type_handle[] = {
>>           {BUF_BIN,         iris_vpu_dec_bin_size         },
>> -        {BUF_COMV,        iris_vpu_dec_comv_size        },
>> +        {BUF_COMV,        iris_vpu3x_4x_dec_comv_size   },
>>           {BUF_NON_COMV,    iris_vpu_dec_non_comv_size    },
>>           {BUF_LINE,        iris_vpu4x_dec_line_size      },
>>           {BUF_PERSIST,     iris_vpu4x_dec_persist_size   },
>> diff --git a/drivers/media/platform/qcom/iris/iris_vpu_buffer.h
>> b/drivers/media/platform/qcom/iris/iris_vpu_buffer.h
>> index 12640eb5ed8c..7a9cc1c92da3 100644
>> --- a/drivers/media/platform/qcom/iris/iris_vpu_buffer.h
>> +++ b/drivers/media/platform/qcom/iris/iris_vpu_buffer.h
>> @@ -110,6 +110,7 @@ struct iris_inst;
>>   #define MAX_PE_NBR_DATA_LCU16_LINE_BUFFER_SIZE 96
>>   #define AV1D_NUM_HW_PIC_BUF    16
>>   #define AV1D_NUM_FRAME_HEADERS 16
>> +#define AV1D_COMV_BUFFER_OVERHEAD 7
>
> Whats this ? Why is there a new seven byte overhead ? Does it represent a
> header, an alignment ?
>
> An overhead can mean anything.
>
>>   #define SIZE_AV1D_SEQUENCE_HEADER 768
>>   #define SIZE_AV1D_METADATA        512
>>   #define SIZE_AV1D_FRAME_HEADER    1280
>>
>> ---
>> base-commit: 4fbeef21f5387234111b5d52924e77757626faa5
>> change-id: 20260421-optimize_comv_buffer-ae7107673609
>>
>> Best regards,
>> -- 
>> Vishnu Reddy <busanna.reddy@oss.qualcomm.com>
>>
>
>