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Subject: Re: [PATCH 1/3] venus: venc: Init the session only once in
 queue_setup
To:     Alexandre Courbot <acourbot@chromium.org>
Cc:     linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Vikash Garodia <vgarodia@codeaurora.org>,
        Mansur Alisha Shaik <mansur@codeaurora.org>,
        Dikshita Agarwal <dikshita@codeaurora.org>
References: <20201120001037.10032-1-stanimir.varbanov@linaro.org>
 <20201120001037.10032-2-stanimir.varbanov@linaro.org>
 <CAPBb6MUU2tKUarrdPennSQ0NVnOUp+jwS3DN3Qye-wiq-aT5_Q@mail.gmail.com>
From:   Stanimir Varbanov <stanimir.varbanov@linaro.org>
Message-ID: <dbd68079-6736-28bf-b9ab-dda51a07aa71@linaro.org>
Date:   Fri, 27 Nov 2020 01:50:58 +0200
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On 11/25/20 5:13 AM, Alexandre Courbot wrote:
> Hi Stan,
> 
> On Fri, Nov 20, 2020 at 9:12 AM Stanimir Varbanov
> <stanimir.varbanov@linaro.org> wrote:
>>
>> Init the hfi session only once in queue_setup and also cover that
>> with inst->lock.
>>
>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
>> ---
>>  drivers/media/platform/qcom/venus/venc.c | 98 ++++++++++++++++++------
>>  1 file changed, 73 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/media/platform/qcom/venus/venc.c b/drivers/media/platform/qcom/venus/venc.c
>> index 4ecf78e30b59..3a2e449663d8 100644
>> --- a/drivers/media/platform/qcom/venus/venc.c
>> +++ b/drivers/media/platform/qcom/venus/venc.c
>> @@ -725,8 +725,10 @@ static int venc_init_session(struct venus_inst *inst)
>>         int ret;
>>
>>         ret = hfi_session_init(inst, inst->fmt_cap->pixfmt);
>> -       if (ret)
>> -               return ret;
>> +       if (ret == -EINVAL)
>> +               return 0;
> 
> Why is it safe to ignore EINVAL here?

The confusion comes from hfi_session_init() return values. Presently
hfi_session_init will return EINVAL when the session is already init.
Maybe EINVAL is not fitting well with the expected behavior of the
function. I thought about EALREADY, EBUSY but it doesn't fit well to me too.

> 
>> +       else if (ret)
>> +               goto deinit;
>>
>>         ret = venus_helper_set_input_resolution(inst, inst->width,
>>                                                 inst->height);
>> @@ -762,17 +764,13 @@ static int venc_out_num_buffers(struct venus_inst *inst, unsigned int *num)
>>         struct hfi_buffer_requirements bufreq;
>>         int ret;
>>
>> -       ret = venc_init_session(inst);
>> +       ret = venus_helper_get_bufreq(inst, HFI_BUFFER_INPUT, &bufreq);
>>         if (ret)
>>                 return ret;
>>
>> -       ret = venus_helper_get_bufreq(inst, HFI_BUFFER_INPUT, &bufreq);
>> -
>>         *num = bufreq.count_actual;
>>
>> -       hfi_session_deinit(inst);
>> -
>> -       return ret;
>> +       return 0;
>>  }
>>
>>  static int venc_queue_setup(struct vb2_queue *q,
>> @@ -781,7 +779,7 @@ static int venc_queue_setup(struct vb2_queue *q,
>>  {
>>         struct venus_inst *inst = vb2_get_drv_priv(q);
>>         unsigned int num, min = 4;
>> -       int ret = 0;
>> +       int ret;
>>
>>         if (*num_planes) {
>>                 if (q->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE &&
>> @@ -803,6 +801,17 @@ static int venc_queue_setup(struct vb2_queue *q,
>>                 return 0;
>>         }
>>
>> +       ret = mutex_lock_interruptible(&inst->lock);

I'll keep original mutex_lock here in next version.

>> +       if (ret)
>> +               return ret;
>> +
>> +       ret = venc_init_session(inst);
>> +
>> +       mutex_unlock(&inst->lock);
>> +
>> +       if (ret)
>> +               return ret;
>> +
>>         switch (q->type) {
>>         case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
>>                 *num_planes = inst->fmt_out->num_planes;
>> @@ -838,6 +847,54 @@ static int venc_queue_setup(struct vb2_queue *q,
>>         return ret;
>>  }
>>
>> +static int venc_buf_init(struct vb2_buffer *vb)
>> +{
>> +       struct venus_inst *inst = vb2_get_drv_priv(vb->vb2_queue);
>> +
>> +       inst->buf_count++;
>> +
>> +       return venus_helper_vb2_buf_init(vb);
>> +}
>> +
>> +static void venc_release_session(struct venus_inst *inst)
>> +{
>> +       int ret, abort = 0;
>> +
>> +       mutex_lock(&inst->lock);
>> +
>> +       ret = hfi_session_deinit(inst);
>> +       abort = (ret && ret != -EINVAL) ? 1 : 0;
> 
> Here as well, I think a comment is warranted to explain why we can
> ignore EINVAL.

OK, will update that.

> 
>> +
>> +       if (inst->session_error)
>> +               abort = 1;
>> +
>> +       if (abort)
>> +               hfi_session_abort(inst);
>> +
>> +       mutex_unlock(&inst->lock);
>> +
>> +       venus_pm_load_scale(inst);
>> +       INIT_LIST_HEAD(&inst->registeredbufs);
>> +       venus_pm_release_core(inst);
>> +}
>> +
>> +static void venc_buf_cleanup(struct vb2_buffer *vb)
>> +{
>> +       struct venus_inst *inst = vb2_get_drv_priv(vb->vb2_queue);
>> +       struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
>> +       struct venus_buffer *buf = to_venus_buffer(vbuf);
>> +
>> +       mutex_lock(&inst->lock);
>> +       if (vb->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE)
>> +               if (!list_empty(&inst->registeredbufs))
>> +                       list_del_init(&buf->reg_list);
>> +       mutex_unlock(&inst->lock);
>> +
>> +       inst->buf_count--;
>> +       if (!inst->buf_count)
>> +               venc_release_session(inst);
> 
> We are calling venc_init_session() during the queue setup but
> venc_release_session() when the last buffer is cleaned up. For
> symmetry, wouldn't it make sense to call venc_init_session() when the
> first buffer is initialized by venc_buf_init()? Otherwise we can

No, the session must be initialized in queue_setup in order to return
the number and sizes of source/destination buffers.

I raised several times the need of symmetrical operation to queue_setup
to cover reqbuf(0) but there is no progress on that. Latest suggestion
was to use .vidioc_reqbufs ioctl op but I fall with some other issues
and at the end I came to this counting buf_init|cleanup solution.

> potentially have a scenario where the queue is set up, but no buffer
> is ever created, leading to the session never being released.

dmabuf import case?

<cut>

-- 
regards,
Stan