Re: [PATCH v6 12/18] media: platform: Add mali-c55 3a stats devnode

[Dan Scally <dan.scally@ideasonboard.com>]

Hi Laurent

On 22/07/2024 15:50, Laurent Pinchart wrote:
> Hi Dan,
>
> Thank you for the patch.
>
> On Tue, Jul 09, 2024 at 02:29:00PM +0100, Daniel Scally wrote:
>> Add a new code file to govern the 3a statistics capture node.
>>
>> Acked-by: Nayden Kanchev  <nayden.kanchev@arm.com>
>> Co-developed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
>> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
>> Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
>> ---
>> Changes in v6:
>>
>> 	- Fixed mising includes
>> 	- Minor renames and formatting
>> 	- Reworked mali_c55_stats_metering_complete() so it could only return
>> 	  buffers when both halves of the DMA read were done
>> 	- Terminate dma transfers on streamoff
>> 	
>> Changes in v5:
>>
>> 	- New patch
>>
>>   drivers/media/platform/arm/mali-c55/Makefile  |   1 +
>>   .../platform/arm/mali-c55/mali-c55-common.h   |  29 ++
>>   .../platform/arm/mali-c55/mali-c55-core.c     |  15 +
>>   .../platform/arm/mali-c55/mali-c55-isp.c      |  11 +
>>   .../arm/mali-c55/mali-c55-registers.h         |   3 +
>>   .../platform/arm/mali-c55/mali-c55-stats.c    | 373 ++++++++++++++++++
>>   6 files changed, 432 insertions(+)
>>   create mode 100644 drivers/media/platform/arm/mali-c55/mali-c55-stats.c
>>
>> diff --git a/drivers/media/platform/arm/mali-c55/Makefile b/drivers/media/platform/arm/mali-c55/Makefile
>> index 9178ac35e50e..b5a22d414479 100644
>> --- a/drivers/media/platform/arm/mali-c55/Makefile
>> +++ b/drivers/media/platform/arm/mali-c55/Makefile
>> @@ -4,6 +4,7 @@ mali-c55-y := mali-c55-capture.o \
>>   	      mali-c55-core.o \
>>   	      mali-c55-isp.o \
>>   	      mali-c55-resizer.o \
>> +	      mali-c55-stats.o \
>>   	      mali-c55-tpg.o
>>   
>>   obj-$(CONFIG_VIDEO_MALI_C55) += mali-c55.o
>> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-common.h b/drivers/media/platform/arm/mali-c55/mali-c55-common.h
>> index f7764a938e9f..136c785c68ba 100644
>> --- a/drivers/media/platform/arm/mali-c55/mali-c55-common.h
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-common.h
>> @@ -49,6 +49,7 @@ enum mali_c55_isp_pads {
>>   	MALI_C55_ISP_PAD_SINK_VIDEO,
>>   	MALI_C55_ISP_PAD_SOURCE_VIDEO,
>>   	MALI_C55_ISP_PAD_SOURCE_BYPASS,
>> +	MALI_C55_ISP_PAD_SOURCE_STATS,
>>   	MALI_C55_ISP_NUM_PADS,
>>   };
>>   
>> @@ -160,6 +161,29 @@ struct mali_c55_cap_dev {
>>   	bool streaming;
>>   };
>>   
>> +struct mali_c55_stats_buf {
>> +	struct vb2_v4l2_buffer vb;
>> +	unsigned int segments_remaining;
>> +	struct list_head queue;
>> +	bool failed;
>> +};
>> +
>> +struct mali_c55_stats {
>> +	struct mali_c55 *mali_c55;
>> +	struct video_device vdev;
>> +	struct dma_chan *channel;
>> +	struct vb2_queue queue;
>> +	struct media_pad pad;
>> +	/* Mutex to provide to vb2 */
>> +	struct mutex lock;
>> +
>> +	struct {
>> +		/* Spinlock to guard buffer queue */
>> +		spinlock_t lock;
>> +		struct list_head queue;
>> +	} buffers;
>> +};
>> +
>>   enum mali_c55_config_spaces {
>>   	MALI_C55_CONFIG_PING,
>>   	MALI_C55_CONFIG_PONG,
>> @@ -202,6 +226,7 @@ struct mali_c55 {
>>   	struct mali_c55_isp isp;
>>   	struct mali_c55_resizer resizers[MALI_C55_NUM_RSZS];
>>   	struct mali_c55_cap_dev cap_devs[MALI_C55_NUM_CAP_DEVS];
>> +	struct mali_c55_stats stats;
>>   
>>   	struct mali_c55_context context;
>>   	enum mali_c55_config_spaces next_config;
>> @@ -229,6 +254,8 @@ int mali_c55_register_resizers(struct mali_c55 *mali_c55);
>>   void mali_c55_unregister_resizers(struct mali_c55 *mali_c55);
>>   int mali_c55_register_capture_devs(struct mali_c55 *mali_c55);
>>   void mali_c55_unregister_capture_devs(struct mali_c55 *mali_c55);
>> +int mali_c55_register_stats(struct mali_c55 *mali_c55);
>> +void mali_c55_unregister_stats(struct mali_c55 *mali_c55);
>>   struct mali_c55_context *mali_c55_get_active_context(struct mali_c55 *mali_c55);
>>   void mali_c55_set_plane_done(struct mali_c55_cap_dev *cap_dev,
>>   			     enum mali_c55_planes plane);
>> @@ -243,5 +270,7 @@ const struct mali_c55_isp_fmt *
>>   mali_c55_isp_get_mbus_config_by_code(u32 code);
>>   const struct mali_c55_isp_fmt *
>>   mali_c55_isp_get_mbus_config_by_index(u32 index);
>> +void mali_c55_stats_fill_buffer(struct mali_c55 *mali_c55,
>> +				enum mali_c55_config_spaces cfg_space);
>>   
>>   #endif /* _MALI_C55_COMMON_H */
>> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-core.c b/drivers/media/platform/arm/mali-c55/mali-c55-core.c
>> index dbc07d12d3a3..eedc8f450184 100644
>> --- a/drivers/media/platform/arm/mali-c55/mali-c55-core.c
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-core.c
>> @@ -374,6 +374,16 @@ static int mali_c55_create_links(struct mali_c55 *mali_c55)
>>   		}
>>   	}
>>   
>> +	ret = media_create_pad_link(&mali_c55->isp.sd.entity,
>> +				    MALI_C55_ISP_PAD_SOURCE_STATS,
>> +				    &mali_c55->stats.vdev.entity, 0,
>> +				    MEDIA_LNK_FL_ENABLED);
>> +	if (ret) {
>> +		dev_err(mali_c55->dev,
>> +			"failed to link ISP and 3a stats node\n");
>> +		goto err_remove_links;
>> +	}
>> +
>>   	return 0;
>>   
>>   err_remove_links:
>> @@ -388,6 +398,7 @@ static void mali_c55_unregister_entities(struct mali_c55 *mali_c55)
>>   	mali_c55_unregister_isp(mali_c55);
>>   	mali_c55_unregister_resizers(mali_c55);
>>   	mali_c55_unregister_capture_devs(mali_c55);
>> +	mali_c55_unregister_stats(mali_c55);
>>   }
>>   
>>   static int mali_c55_register_entities(struct mali_c55 *mali_c55)
>> @@ -410,6 +421,10 @@ static int mali_c55_register_entities(struct mali_c55 *mali_c55)
>>   	if (ret)
>>   		goto err_unregister_entities;
>>   
>> +	ret = mali_c55_register_stats(mali_c55);
>> +	if (ret)
>> +		goto err_unregister_entities;
>> +
>>   	ret = mali_c55_create_links(mali_c55);
>>   	if (ret)
>>   		goto err_unregister_entities;
>> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-isp.c b/drivers/media/platform/arm/mali-c55/mali-c55-isp.c
>> index f784983a4ccc..2f450c00300a 100644
>> --- a/drivers/media/platform/arm/mali-c55/mali-c55-isp.c
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-isp.c
>> @@ -5,6 +5,8 @@
>>    * Copyright (C) 2024 Ideas on Board Oy
>>    */
>>   
>> +#include <linux/media/arm/mali-c55-config.h>
>> +
>>   #include <linux/delay.h>
>>   #include <linux/iopoll.h>
>>   #include <linux/property.h>
>> @@ -460,6 +462,14 @@ static int mali_c55_isp_init_state(struct v4l2_subdev *sd,
>>   	in_crop->width = MALI_C55_DEFAULT_WIDTH;
>>   	in_crop->height = MALI_C55_DEFAULT_HEIGHT;
>>   
>> +	src_fmt = v4l2_subdev_state_get_format(state,
>> +					       MALI_C55_ISP_PAD_SOURCE_STATS);
>> +
>> +	src_fmt->width = sizeof(struct mali_c55_stats_buffer);
>> +	src_fmt->height = 1;
> According to
> https://docs.kernel.org/userspace-api/media/v4l/subdev-formats.html#metadata-formats,
> width and height should be set to 0 for MEDIA_BUS_FMT_METADATA_FIXED. I
> haven't checked if v4l2-compliance expects this, we may have
> discrepancies between the API documentation and the existing
> implementations in the kernel and userspace. In any case, this should be
> sorted out, either by fixing the kernel code and enforcing the
> requirement in v4l2-compliance, or fixing the documentation.


Ah. I can't completely remember why I set these to other-than-zero. When I refresh the series I'll 
figure out what spurred this, and then we can address v4l2-compliance / the documentation.

>
>> +	src_fmt->field = V4L2_FIELD_NONE;
>> +	src_fmt->code = MEDIA_BUS_FMT_METADATA_FIXED;
>> +
>>   	return 0;
>>   }
>>   
>> @@ -490,6 +500,7 @@ int mali_c55_register_isp(struct mali_c55 *mali_c55)
>>   						       MEDIA_PAD_FL_MUST_CONNECT;
>>   	isp->pads[MALI_C55_ISP_PAD_SOURCE_VIDEO].flags = MEDIA_PAD_FL_SOURCE;
>>   	isp->pads[MALI_C55_ISP_PAD_SOURCE_BYPASS].flags = MEDIA_PAD_FL_SOURCE;
>> +	isp->pads[MALI_C55_ISP_PAD_SOURCE_STATS].flags = MEDIA_PAD_FL_SOURCE;
>>   
>>   	ret = media_entity_pads_init(&sd->entity, MALI_C55_ISP_NUM_PADS,
>>   				     isp->pads);
>> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-registers.h b/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
>> index 0a391f8a043e..e72e749b81d5 100644
>> --- a/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
>> @@ -103,6 +103,9 @@ enum mali_c55_interrupts {
>>   #define MALI_C55_VC_START(v)				((v) & 0xffff)
>>   #define MALI_C55_VC_SIZE(v)				(((v) & 0xffff) << 16)
>>   
>> +#define MALI_C55_REG_1024BIN_HIST			0x054a8
>> +#define MALI_C55_1024BIN_HIST_SIZE			4096
>> +
>>   /* Ping/Pong Configuration Space */
>>   #define MALI_C55_REG_BASE_ADDR				0x18e88
>>   #define MALI_C55_REG_BYPASS_0				0x18eac
>> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-stats.c b/drivers/media/platform/arm/mali-c55/mali-c55-stats.c
>> new file mode 100644
>> index 000000000000..38a17fb5d052
>> --- /dev/null
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-stats.c
>> @@ -0,0 +1,373 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * ARM Mali-C55 ISP Driver - 3A Statistics capture device
>> + *
>> + * Copyright (C) 2023 Ideas on Board Oy
>> + */
>> +
>> +#include <linux/container_of.h>
>> +#include <linux/dev_printk.h>
>> +#include <linux/dmaengine.h>
>> +#include <linux/list.h>
>> +#include <linux/media/arm/mali-c55-config.h>
>> +#include <linux/mutex.h>
>> +#include <linux/spinlock.h>
>> +#include <linux/string.h>
>> +
>> +#include <media/media-entity.h>
>> +#include <media/v4l2-dev.h>
>> +#include <media/v4l2-event.h>
>> +#include <media/v4l2-fh.h>
>> +#include <media/v4l2-ioctl.h>
>> +#include <media/videobuf2-core.h>
>> +#include <media/videobuf2-dma-contig.h>
>> +
>> +#include "mali-c55-common.h"
>> +#include "mali-c55-registers.h"
>> +
>> +static const unsigned int metering_space_addrs[] = {
>> +	[MALI_C55_CONFIG_PING] = 0x095ac,
>> +	[MALI_C55_CONFIG_PONG] = 0x2156c,
>> +};
>> +
>> +static int mali_c55_stats_enum_fmt_meta_cap(struct file *file, void *fh,
>> +					    struct v4l2_fmtdesc *f)
>> +{
>> +	if (f->index)
>> +		return -EINVAL;
>> +
>> +	f->pixelformat = V4L2_META_FMT_MALI_C55_STATS;
>> +
>> +	return 0;
>> +}
>> +
>> +static int mali_c55_stats_g_fmt_meta_cap(struct file *file, void *fh,
>> +					 struct v4l2_format *f)
>> +{
>> +	static const struct v4l2_meta_format mfmt = {
>> +		.dataformat = V4L2_META_FMT_MALI_C55_STATS,
>> +		.buffersize = sizeof(struct mali_c55_stats_buffer)
>> +	};
>> +
>> +	f->fmt.meta = mfmt;
>> +
>> +	return 0;
>> +}
>> +
>> +static int mali_c55_stats_querycap(struct file *file,
>> +				   void *priv, struct v4l2_capability *cap)
>> +{
>> +	strscpy(cap->driver, MALI_C55_DRIVER_NAME, sizeof(cap->driver));
>> +	strscpy(cap->card, "ARM Mali-C55 ISP", sizeof(cap->card));
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct v4l2_ioctl_ops mali_c55_stats_v4l2_ioctl_ops = {
>> +	.vidioc_reqbufs = vb2_ioctl_reqbufs,
>> +	.vidioc_querybuf = vb2_ioctl_querybuf,
>> +	.vidioc_create_bufs = vb2_ioctl_create_bufs,
>> +	.vidioc_qbuf = vb2_ioctl_qbuf,
>> +	.vidioc_expbuf = vb2_ioctl_expbuf,
>> +	.vidioc_dqbuf = vb2_ioctl_dqbuf,
>> +	.vidioc_prepare_buf = vb2_ioctl_prepare_buf,
>> +	.vidioc_streamon = vb2_ioctl_streamon,
>> +	.vidioc_streamoff = vb2_ioctl_streamoff,
>> +	.vidioc_enum_fmt_meta_cap = mali_c55_stats_enum_fmt_meta_cap,
>> +	.vidioc_g_fmt_meta_cap = mali_c55_stats_g_fmt_meta_cap,
>> +	.vidioc_s_fmt_meta_cap = mali_c55_stats_g_fmt_meta_cap,
>> +	.vidioc_try_fmt_meta_cap = mali_c55_stats_g_fmt_meta_cap,
>> +	.vidioc_querycap = mali_c55_stats_querycap,
>> +	.vidioc_subscribe_event = v4l2_ctrl_subscribe_event,
>> +	.vidioc_unsubscribe_event = v4l2_event_unsubscribe,
>> +};
>> +
>> +static const struct v4l2_file_operations mali_c55_stats_v4l2_fops = {
>> +	.owner = THIS_MODULE,
>> +	.unlocked_ioctl = video_ioctl2,
>> +	.open = v4l2_fh_open,
>> +	.release = vb2_fop_release,
>> +	.poll = vb2_fop_poll,
>> +	.mmap = vb2_fop_mmap,
>> +};
>> +
>> +static int
>> +mali_c55_stats_queue_setup(struct vb2_queue *q, unsigned int *num_buffers,
>> +			   unsigned int *num_planes, unsigned int sizes[],
>> +			   struct device *alloc_devs[])
>> +{
>> +	struct mali_c55_stats *stats = vb2_get_drv_priv(q);
>> +
>> +	if (*num_planes && *num_planes > 1)
>> +		return -EINVAL;
>> +
>> +	if (sizes[0] && sizes[0] < sizeof(struct mali_c55_stats_buffer))
>> +		return -EINVAL;
>> +
>> +	*num_planes = 1;
>> +
>> +	if (!sizes[0])
>> +		sizes[0] = sizeof(struct mali_c55_stats_buffer);
>> +
>> +	if (stats->channel)
>> +		alloc_devs[0] = stats->channel->device->dev;
>> +
>> +	return 0;
>> +}
>> +
>> +static void mali_c55_stats_buf_queue(struct vb2_buffer *vb)
>> +{
>> +	struct mali_c55_stats *stats = vb2_get_drv_priv(vb->vb2_queue);
>> +	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
>> +	struct mali_c55_stats_buf *buf = container_of(vbuf,
>> +						struct mali_c55_stats_buf, vb);
>> +
>> +	vb2_set_plane_payload(vb, 0, sizeof(struct mali_c55_stats_buffer));
>> +	buf->segments_remaining = 2;
>> +	buf->failed = false;
>> +
>> +	spin_lock(&stats->buffers.lock);
>> +	list_add_tail(&buf->queue, &stats->buffers.queue);
>> +	spin_unlock(&stats->buffers.lock);
>> +}
>> +
>> +static int mali_c55_stats_start_streaming(struct vb2_queue *q,
>> +					  unsigned int count)
>> +{
>> +	struct mali_c55_stats *stats = vb2_get_drv_priv(q);
>> +	struct mali_c55 *mali_c55 = stats->mali_c55;
>> +	int ret;
>> +
>> +	ret = video_device_pipeline_start(&stats->vdev,
>> +					  &stats->mali_c55->pipe);
>> +	if (ret)
>> +		return ret;
>> +
>> +	if (mali_c55->pipe.start_count == mali_c55->pipe.required_count) {
>> +		ret = v4l2_subdev_enable_streams(&mali_c55->isp.sd,
>> +						 MALI_C55_ISP_PAD_SOURCE_VIDEO,
>> +						 BIT(0));
>> +		if (ret)
>> +			goto err_stop_pipeline;
>> +	}
>> +
>> +	return 0;
>> +
>> +err_stop_pipeline:
>> +	video_device_pipeline_stop(&stats->vdev);
>> +
>> +	return ret;
>> +}
>> +
>> +static void mali_c55_stats_stop_streaming(struct vb2_queue *q)
>> +{
>> +	struct mali_c55_stats *stats = vb2_get_drv_priv(q);
>> +	struct mali_c55_stats_buf *buf, *tmp;
>> +
>> +	dmaengine_terminate_sync(stats->channel);
>> +
>> +	spin_lock(&stats->buffers.lock);
>> +
>> +	list_for_each_entry_safe(buf, tmp, &stats->buffers.queue, queue) {
>> +		list_del(&buf->queue);
>> +		vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
>> +	}
>> +
>> +	spin_unlock(&stats->buffers.lock);
>> +
>> +	video_device_pipeline_stop(&stats->vdev);
>> +}
>> +
>> +static const struct vb2_ops mali_c55_stats_vb2_ops = {
>> +	.queue_setup = mali_c55_stats_queue_setup,
>> +	.buf_queue = mali_c55_stats_buf_queue,
>> +	.wait_prepare = vb2_ops_wait_prepare,
>> +	.wait_finish = vb2_ops_wait_finish,
>> +	.start_streaming = mali_c55_stats_start_streaming,
>> +	.stop_streaming = mali_c55_stats_stop_streaming,
>> +};
>> +
>> +static void
>> +mali_c55_stats_metering_complete(void *param,
>> +				 const struct dmaengine_result *result)
>> +{
>> +	struct mali_c55_stats_buf *buf = param;
>> +
>> +	if (result->result != DMA_TRANS_NOERROR)
>> +		buf->failed = true;
>> +
>> +	if (!--buf->segments_remaining)
>> +		vb2_buffer_done(&buf->vb.vb2_buf, buf->failed ?
>> +				VB2_BUF_STATE_ERROR : VB2_BUF_STATE_DONE);
>> +}
>> +
>> +static int mali_c55_stats_dma_xfer(struct mali_c55_stats *stats, dma_addr_t src,
>> +				   dma_addr_t dst,
>> +				   struct mali_c55_stats_buf *buf,
>> +				   size_t length)
>> +{
>> +	struct dma_async_tx_descriptor *tx;
>> +	dma_cookie_t cookie;
>> +
>> +	tx = dmaengine_prep_dma_memcpy(stats->channel, dst, src, length, 0);
>> +	if (!tx) {
>> +		dev_err(stats->mali_c55->dev, "failed to prep stats DMA\n");
>> +		return -EIO;
>> +	}
>> +
>> +	tx->callback_result = mali_c55_stats_metering_complete;
>> +	tx->callback_param = buf;
>> +
>> +	cookie = dmaengine_submit(tx);
>> +	if (dma_submit_error(cookie)) {
>> +		dev_err(stats->mali_c55->dev, "failed to submit stats DMA\n");
>> +		return -EIO;
>> +	}
>> +
>> +	dma_async_issue_pending(stats->channel);
>> +	return 0;
>> +}
>> +
>> +void mali_c55_stats_fill_buffer(struct mali_c55 *mali_c55,
>> +				enum mali_c55_config_spaces cfg_space)
>> +{
>> +	struct mali_c55_context *ctx = mali_c55_get_active_context(mali_c55);
>> +	struct mali_c55_stats *stats = &mali_c55->stats;
>> +	struct mali_c55_stats_buf *buf = NULL;
>> +	dma_addr_t src, dst;
>> +	size_t length;
>> +	int ret;
>> +
>> +	spin_lock(&stats->buffers.lock);
>> +	if (!list_empty(&stats->buffers.queue)) {
>> +		buf = list_first_entry(&stats->buffers.queue,
>> +				       struct mali_c55_stats_buf, queue);
>> +		list_del(&buf->queue);
>> +	}
>> +	spin_unlock(&stats->buffers.lock);
>> +
>> +	if (!buf)
>> +		return;
>> +
>> +	buf->vb.sequence = mali_c55->isp.frame_sequence;
>> +	buf->vb.vb2_buf.timestamp = ktime_get_boottime_ns();
>> +
>> +	/*
>> +	 * There are in fact two noncontiguous sections of the ISP's
>> +	 * memory space that hold statistics for 3a algorithms to use: A
>> +	 * section in each config space and a global section holding
>> +	 * histograms which is double buffered and so holds data for the
>> +	 * last frame. We need to read both.
>> +	 */
>> +	src = ctx->base + MALI_C55_REG_1024BIN_HIST;
>> +	dst = vb2_dma_contig_plane_dma_addr(&buf->vb.vb2_buf, 0);
>> +
>> +	ret = mali_c55_stats_dma_xfer(stats, src, dst, buf,
>> +				      MALI_C55_1024BIN_HIST_SIZE);
>> +	if (ret)
>> +		goto err_fail_buffer;
>> +
>> +	src = ctx->base + metering_space_addrs[cfg_space];
>> +	dst += MALI_C55_1024BIN_HIST_SIZE;
>> +
>> +	length = sizeof(struct mali_c55_stats_buffer) - MALI_C55_1024BIN_HIST_SIZE;
>> +	ret = mali_c55_stats_dma_xfer(stats, src, dst, buf, length);
>> +	if (ret) {
>> +		dmaengine_terminate_sync(stats->channel);
>> +		goto err_fail_buffer;
>> +	}
>> +
>> +	return;
>> +
>> +err_fail_buffer:
>> +	vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
>> +}
>> +
>> +void mali_c55_unregister_stats(struct mali_c55 *mali_c55)
>> +{
>> +	struct mali_c55_stats *stats = &mali_c55->stats;
>> +
>> +	if (!video_is_registered(&stats->vdev))
>> +		return;
>> +
>> +	vb2_video_unregister_device(&stats->vdev);
>> +	media_entity_cleanup(&stats->vdev.entity);
>> +	dma_release_channel(stats->channel);
>> +	mutex_destroy(&stats->lock);
>> +}
>> +
>> +int mali_c55_register_stats(struct mali_c55 *mali_c55)
>> +{
>> +	struct mali_c55_stats *stats = &mali_c55->stats;
>> +	struct video_device *vdev = &stats->vdev;
>> +	struct vb2_queue *vb2q = &stats->queue;
>> +	dma_cap_mask_t mask;
>> +	int ret;
>> +
>> +	mutex_init(&stats->lock);
>> +	INIT_LIST_HEAD(&stats->buffers.queue);
>> +
>> +	dma_cap_zero(mask);
>> +	dma_cap_set(DMA_MEMCPY, mask);
>> +
>> +	stats->channel = dma_request_channel(mask, 0, NULL);
>> +	if (!stats->channel) {
>> +		ret = -ENODEV;
>> +		goto err_destroy_mutex;
>> +	}
>> +
>> +	stats->pad.flags = MEDIA_PAD_FL_SINK;
>> +	ret = media_entity_pads_init(&stats->vdev.entity, 1, &stats->pad);
>> +	if (ret)
>> +		goto err_release_dma_channel;
>> +
>> +	vb2q->type = V4L2_BUF_TYPE_META_CAPTURE;
>> +	vb2q->io_modes = VB2_MMAP | VB2_DMABUF;
>> +	vb2q->drv_priv = stats;
>> +	vb2q->mem_ops = &vb2_dma_contig_memops;
>> +	vb2q->ops = &mali_c55_stats_vb2_ops;
>> +	vb2q->buf_struct_size = sizeof(struct mali_c55_stats_buf);
>> +	vb2q->min_queued_buffers = 1;
>> +	vb2q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
>> +	vb2q->lock = &stats->lock;
>> +	vb2q->dev = stats->channel->device->dev;
>> +
>> +	ret = vb2_queue_init(vb2q);
>> +	if (ret) {
>> +		dev_err(mali_c55->dev, "stats vb2 queue init failed\n");
>> +		goto err_cleanup_entity;
>> +	}
>> +
>> +	strscpy(stats->vdev.name, "mali-c55 3a stats", sizeof(stats->vdev.name));
>> +	vdev->release = video_device_release_empty;
>> +	vdev->fops = &mali_c55_stats_v4l2_fops;
>> +	vdev->ioctl_ops = &mali_c55_stats_v4l2_ioctl_ops;
>> +	vdev->lock = &stats->lock;
>> +	vdev->v4l2_dev = &mali_c55->v4l2_dev;
>> +	vdev->queue = &stats->queue;
>> +	vdev->device_caps = V4L2_CAP_META_CAPTURE | V4L2_CAP_STREAMING;
>> +	vdev->vfl_dir = VFL_DIR_RX;
>> +	video_set_drvdata(vdev, stats);
>> +
>> +	ret = video_register_device(vdev, VFL_TYPE_VIDEO, -1);
>> +	if (ret) {
>> +		dev_err(mali_c55->dev,
>> +			"failed to register stats video device\n");
>> +		goto err_release_vb2q;
>> +	}
>> +
>> +	stats->mali_c55 = mali_c55;
>> +
>> +	return 0;
>> +
>> +err_release_vb2q:
>> +	vb2_queue_release(vb2q);
>> +err_cleanup_entity:
>> +	media_entity_cleanup(&stats->vdev.entity);
>> +err_release_dma_channel:
>> +	dma_release_channel(stats->channel);
>> +err_destroy_mutex:
>> +	mutex_destroy(&stats->lock);
>> +
>> +	return ret;
>> +}