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Subject: Re: [PATCH v3 3/3] media: stm32-dcmi: add support of several
 sub-devices
To:     Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc:     Hugues Fruchet <hugues.fruchet@st.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        linux-media@vger.kernel.org,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-stm32@st-md-mailman.stormreply.com,
        Yannick Fertre <yannick.fertre@st.com>,
        Philippe CORNU <philippe.cornu@st.com>,
        Mickael GUENE <mickael.guene@st.com>
References: <1562082779-31165-1-git-send-email-hugues.fruchet@st.com>
 <1562082779-31165-4-git-send-email-hugues.fruchet@st.com>
 <81e1a94d-af25-302c-64a6-3cec096d4144@xs4all.nl>
 <CA+M3ks7HRc2C+dFpS9AM8ANo+=f360SFTCRrjavbqjd_SWkr_A@mail.gmail.com>
From:   Hans Verkuil <hverkuil@xs4all.nl>
Message-ID: <7c18a314-851b-2852-83be-406cdc2f2047@xs4all.nl>
Date:   Thu, 25 Jul 2019 17:09:01 +0200
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On 7/25/19 4:56 PM, Benjamin Gaignard wrote:
> Le jeu. 25 juil. 2019 à 13:40, Hans Verkuil <hverkuil@xs4all.nl> a écrit :
>>
>> On 7/2/19 5:52 PM, Hugues Fruchet wrote:
>>> Add support of several sub-devices within pipeline instead
>>> of a single one.
>>> This allows to support a CSI-2 camera sensor connected
>>> through a CSI-2 to parallel bridge.
>>>
>>> Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
>>> ---
>>>  drivers/media/platform/stm32/stm32-dcmi.c | 204 +++++++++++++++++++++++++++---
>>>  1 file changed, 186 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
>>> index 6f37617..6921e6b 100644
>>> --- a/drivers/media/platform/stm32/stm32-dcmi.c
>>> +++ b/drivers/media/platform/stm32/stm32-dcmi.c
>>> @@ -172,6 +172,7 @@ struct stm32_dcmi {
>>>
>>>       struct media_device             mdev;
>>>       struct media_pad                vid_cap_pad;
>>> +     struct media_pipeline           pipeline;
>>>  };
>>>
>>>  static inline struct stm32_dcmi *notifier_to_dcmi(struct v4l2_async_notifier *n)
>>> @@ -583,6 +584,131 @@ static void dcmi_buf_queue(struct vb2_buffer *vb)
>>>       spin_unlock_irq(&dcmi->irqlock);
>>>  }
>>>
>>> +static struct media_entity *dcmi_find_source(struct stm32_dcmi *dcmi)
>>> +{
>>> +     struct media_entity *entity = &dcmi->vdev->entity;
>>> +     struct media_pad *pad;
>>> +
>>> +     /* Walk searching for entity having no sink */
>>> +     while (1) {
>>> +             pad = &entity->pads[0];
>>> +             if (!(pad->flags & MEDIA_PAD_FL_SINK))
>>> +                     break;
>>> +
>>> +             pad = media_entity_remote_pad(pad);
>>> +             if (!pad || !is_media_entity_v4l2_subdev(pad->entity))
>>> +                     break;
>>> +
>>> +             entity = pad->entity;
>>> +     }
>>> +
>>> +     return entity;
>>> +}
>>> +
>>> +static int dcmi_pipeline_s_fmt(struct stm32_dcmi *dcmi,
>>> +                            struct v4l2_subdev_pad_config *pad_cfg,
>>> +                            struct v4l2_subdev_format *format)
>>> +{
>>> +     struct media_entity *entity = &dcmi->entity.source->entity;
>>> +     struct v4l2_subdev *subdev;
>>> +     struct media_pad *sink_pad = NULL;
>>> +     struct media_pad *src_pad = NULL;
>>> +     struct media_pad *pad = NULL;
>>> +     struct v4l2_subdev_format fmt = *format;
>>> +     bool found = false;
>>> +     int ret;
>>> +
>>> +     /*
>>> +      * Starting from sensor subdevice, walk within
>>> +      * pipeline and set format on each subdevice
>>> +      */
>>> +     while (1) {
>>> +             unsigned int i;
>>> +
>>> +             /* Search if current entity has a source pad */
>>> +             for (i = 0; i < entity->num_pads; i++) {
>>> +                     pad = &entity->pads[i];
>>> +                     if (pad->flags & MEDIA_PAD_FL_SOURCE) {
>>> +                             src_pad = pad;
>>> +                             found = true;
>>> +                             break;
>>> +                     }
>>> +             }
>>> +             if (!found)
>>> +                     break;
>>> +
>>> +             subdev = media_entity_to_v4l2_subdev(entity);
>>> +
>>> +             /* Propagate format on sink pad if any, otherwise source pad */
>>> +             if (sink_pad)
>>> +                     pad = sink_pad;
>>> +
>>> +             dev_dbg(dcmi->dev, "%s[%d] pad format set to 0x%x %ux%u\n",
>>> +                     subdev->name, pad->index, format->format.code,
>>> +                     format->format.width, format->format.height);
>>> +
>>> +             fmt.pad = pad->index;
>>> +             ret = v4l2_subdev_call(subdev, pad, set_fmt, pad_cfg, &fmt);
>>> +             if (ret < 0)
>>> +                     return ret;
>>> +
>>> +             /* Walk to next entity */
>>> +             sink_pad = media_entity_remote_pad(src_pad);
>>> +             if (!sink_pad || !is_media_entity_v4l2_subdev(sink_pad->entity))
>>> +                     break;
>>> +
>>> +             entity = sink_pad->entity;
>>> +     }
>>> +     *format = fmt;
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int dcmi_pipeline_s_stream(struct stm32_dcmi *dcmi, int state)
>>> +{
>>> +     struct media_entity *entity = &dcmi->vdev->entity;
>>> +     struct v4l2_subdev *subdev;
>>> +     struct media_pad *pad;
>>> +     int ret;
>>> +
>>> +     /* Start/stop all entities within pipeline */
>>> +     while (1) {
>>> +             pad = &entity->pads[0];
>>> +             if (!(pad->flags & MEDIA_PAD_FL_SINK))
>>> +                     break;
>>> +
>>> +             pad = media_entity_remote_pad(pad);
>>> +             if (!pad || !is_media_entity_v4l2_subdev(pad->entity))
>>> +                     break;
>>> +
>>> +             entity = pad->entity;
>>> +             subdev = media_entity_to_v4l2_subdev(entity);
>>> +
>>> +             ret = v4l2_subdev_call(subdev, video, s_stream, state);
>>> +             if (ret < 0 && ret != -ENOIOCTLCMD) {
>>> +                     dev_err(dcmi->dev, "%s: %s failed to %s streaming (%d)\n",
>>> +                             __func__, subdev->name,
>>> +                             state ? "start" : "stop", ret);
>>> +                     return ret;
>>> +             }
>>> +
>>> +             dev_dbg(dcmi->dev, "%s is %s\n",
>>> +                     subdev->name, state ? "started" : "stopped");
>>> +     }
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int dcmi_pipeline_start(struct stm32_dcmi *dcmi)
>>> +{
>>> +     return dcmi_pipeline_s_stream(dcmi, 1);
>>> +}
>>> +
>>> +static void dcmi_pipeline_stop(struct stm32_dcmi *dcmi)
>>> +{
>>> +     dcmi_pipeline_s_stream(dcmi, 0);
>>> +}
>>> +
>>>  static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
>>>  {
>>>       struct stm32_dcmi *dcmi = vb2_get_drv_priv(vq);
>>> @@ -597,14 +723,17 @@ static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
>>>               goto err_release_buffers;
>>>       }
>>>
>>> -     /* Enable stream on the sub device */
>>> -     ret = v4l2_subdev_call(dcmi->entity.source, video, s_stream, 1);
>>> -     if (ret && ret != -ENOIOCTLCMD) {
>>> -             dev_err(dcmi->dev, "%s: Failed to start streaming, subdev streamon error",
>>> -                     __func__);
>>> +     ret = media_pipeline_start(&dcmi->vdev->entity, &dcmi->pipeline);
>>> +     if (ret < 0) {
>>> +             dev_err(dcmi->dev, "%s: Failed to start streaming, media pipeline start error (%d)\n",
>>> +                     __func__, ret);
>>>               goto err_pm_put;
>>>       }
>>>
>>> +     ret = dcmi_pipeline_start(dcmi);
>>> +     if (ret)
>>> +             goto err_media_pipeline_stop;
>>> +
>>>       spin_lock_irq(&dcmi->irqlock);
>>>
>>>       /* Set bus width */
>>> @@ -676,7 +805,7 @@ static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
>>>       if (ret) {
>>>               dev_err(dcmi->dev, "%s: Start streaming failed, cannot start capture\n",
>>>                       __func__);
>>> -             goto err_subdev_streamoff;
>>> +             goto err_pipeline_stop;
>>>       }
>>>
>>>       /* Enable interruptions */
>>> @@ -687,8 +816,11 @@ static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
>>>
>>>       return 0;
>>>
>>> -err_subdev_streamoff:
>>> -     v4l2_subdev_call(dcmi->entity.source, video, s_stream, 0);
>>> +err_pipeline_stop:
>>> +     dcmi_pipeline_stop(dcmi);
>>> +
>>> +err_media_pipeline_stop:
>>> +     media_pipeline_stop(&dcmi->vdev->entity);
>>>
>>>  err_pm_put:
>>>       pm_runtime_put(dcmi->dev);
>>> @@ -713,13 +845,10 @@ static void dcmi_stop_streaming(struct vb2_queue *vq)
>>>  {
>>>       struct stm32_dcmi *dcmi = vb2_get_drv_priv(vq);
>>>       struct dcmi_buf *buf, *node;
>>> -     int ret;
>>>
>>> -     /* Disable stream on the sub device */
>>> -     ret = v4l2_subdev_call(dcmi->entity.source, video, s_stream, 0);
>>> -     if (ret && ret != -ENOIOCTLCMD)
>>> -             dev_err(dcmi->dev, "%s: Failed to stop streaming, subdev streamoff error (%d)\n",
>>> -                     __func__, ret);
>>> +     dcmi_pipeline_stop(dcmi);
>>> +
>>> +     media_pipeline_stop(&dcmi->vdev->entity);
>>>
>>>       spin_lock_irq(&dcmi->irqlock);
>>>
>>> @@ -937,8 +1066,7 @@ static int dcmi_set_fmt(struct stm32_dcmi *dcmi, struct v4l2_format *f)
>>>       mf->width = sd_framesize.width;
>>>       mf->height = sd_framesize.height;
>>>
>>> -     ret = v4l2_subdev_call(dcmi->entity.source, pad,
>>> -                            set_fmt, NULL, &format);
>>> +     ret = dcmi_pipeline_s_fmt(dcmi, NULL, &format);
>>>       if (ret < 0)
>>>               return ret;
>>>
>>> @@ -1529,7 +1657,20 @@ static int dcmi_graph_notify_complete(struct v4l2_async_notifier *notifier)
>>>       struct stm32_dcmi *dcmi = notifier_to_dcmi(notifier);
>>>       int ret;
>>>
>>> +     /*
>>> +      * Now that the graph is complete,
>>> +      * we search for the source subdevice
>>> +      * in order to expose it through V4L2 interface
>>> +      */
>>> +     dcmi->entity.source =
>>> +             media_entity_to_v4l2_subdev(dcmi_find_source(dcmi));
>>> +     if (!dcmi->entity.source) {
>>> +             dev_err(dcmi->dev, "Source subdevice not found\n");
>>> +             return -ENODEV;
>>> +     }
>>> +
>>>       dcmi->vdev->ctrl_handler = dcmi->entity.source->ctrl_handler;
>>> +
>>>       ret = dcmi_formats_init(dcmi);
>>>       if (ret) {
>>>               dev_err(dcmi->dev, "No supported mediabus format found\n");
>>> @@ -1574,12 +1715,30 @@ static int dcmi_graph_notify_bound(struct v4l2_async_notifier *notifier,
>>>                                  struct v4l2_async_subdev *asd)
>>>  {
>>>       struct stm32_dcmi *dcmi = notifier_to_dcmi(notifier);
>>> +     unsigned int ret;
>>> +     int src_pad;
>>>
>>>       dev_dbg(dcmi->dev, "Subdev %s bound\n", subdev->name);
>>>
>>> -     dcmi->entity.source = subdev;
>>> +     /*
>>> +      * Link this sub-device to DCMI, it could be
>>> +      * a parallel camera sensor or a bridge
>>> +      */
>>> +     src_pad = media_entity_get_fwnode_pad(&subdev->entity,
>>> +                                           subdev->fwnode,
>>> +                                           MEDIA_PAD_FL_SOURCE);
>>> +
>>> +     ret = media_create_pad_link(&subdev->entity, src_pad,
>>> +                                 &dcmi->vdev->entity, 0,
>>> +                                 MEDIA_LNK_FL_IMMUTABLE |
>>> +                                 MEDIA_LNK_FL_ENABLED);
>>> +     if (ret)
>>> +             dev_err(dcmi->dev, "Failed to create media pad link with subdev %s\n",
>>> +                     subdev->name);
>>> +     else
>>> +             dev_dbg(dcmi->dev, "DCMI is now linked to %s\n", subdev->name);
>>>
>>> -     return 0;
>>> +     return ret;
>>>  }
>>>
>>>  static const struct v4l2_async_notifier_operations dcmi_graph_notify_ops = {
>>> @@ -1639,6 +1798,15 @@ static int dcmi_graph_init(struct stm32_dcmi *dcmi)
>>>               return ret;
>>>       }
>>>
>>> +     /* Register all the subdev nodes */
>>> +     ret = v4l2_device_register_subdev_nodes(&dcmi->v4l2_dev);
>>
>> This shouldn't be needed. Only MC-centric drivers (i.e. where the pipeline
>> has to be configured by userspace) need to do this.
> 
> Hi Hans,
> I think this point has been discussed in this thread
> https://www.spinics.net/lists/linux-media/msg153417.html
> 
> In short : since the hardware only offer one possible path we don't expose
> the configuration to userland and let DCMI driver configure the
> subdevice (like bridge).

Yes, and I agree completely. But why then do you register v4l-subdevX devices?
That's not needed for this driver.

Regards,

	Hans

> 
> Benjamin
> 
>>
>> Otherwise this patch looks good.
>>
>> Regards,
>>
>>         Hans
>>
>>> +     if (ret) {
>>> +             dev_err(dcmi->dev, "Failed to register subdev nodes\n");
>>> +             v4l2_async_notifier_unregister(&dcmi->notifier);
>>> +             of_node_put(dcmi->entity.remote_node);
>>> +             return ret;
>>> +     }
>>> +
>>>       return 0;
>>>  }
>>>
>>>
>>