[PATCH v5 10/16] media: platform: Add mali-c55 3a stats devnode
Dan Scally
dan.scally at ideasonboard.com
Thu Jun 20 08:10:01 PDT 2024
Hi Laurent
On 16/06/2024 22:19, Laurent Pinchart wrote:
> Hi Dan,
>
> Thank you for the patch.
>
> On Wed, May 29, 2024 at 04:28:52PM +0100, Daniel Scally wrote:
>> Add a new code file to govern the 3a statistics capture node.
>>
>> Acked-by: Nayden Kanchev <nayden.kanchev at arm.com>
>> Co-developed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
>> Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
>> Signed-off-by: Daniel Scally <dan.scally at ideasonboard.com>
>> ---
>> Changes in v5:
>>
>> - New patch
>>
>> drivers/media/platform/arm/mali-c55/Makefile | 3 +-
>> .../platform/arm/mali-c55/mali-c55-common.h | 28 ++
>> .../platform/arm/mali-c55/mali-c55-core.c | 15 +
>> .../platform/arm/mali-c55/mali-c55-isp.c | 1 +
>> .../arm/mali-c55/mali-c55-registers.h | 3 +
>> .../platform/arm/mali-c55/mali-c55-stats.c | 350 ++++++++++++++++++
>> 6 files changed, 399 insertions(+), 1 deletion(-)
>> 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 77dcb2fbf0f4..cd5a64bf0c62 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-tpg.o \
>> - mali-c55-resizer.o
>> + mali-c55-resizer.o \
>> + mali-c55-stats.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 2d0c4d152beb..44119e04009b 100644
>> --- a/drivers/media/platform/arm/mali-c55/mali-c55-common.h
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-common.h
>> @@ -79,6 +79,7 @@ enum mali_c55_isp_pads {
>> MALI_C55_ISP_PAD_SINK_VIDEO,
>> MALI_C55_ISP_PAD_SOURCE,
>> MALI_C55_ISP_PAD_SOURCE_BYPASS,
>> + MALI_C55_ISP_PAD_SOURCE_3A,
> Functions and structures are named with a "stats" suffix, let's call
> this MALI_C55_ISP_PAD_SOURCE_STATS.
>
>> MALI_C55_ISP_NUM_PADS,
>> };
>>
>> @@ -194,6 +195,28 @@ struct mali_c55_cap_dev {
>> bool streaming;
>> };
>>
>> +struct mali_c55_stats_buf {
>> + struct vb2_v4l2_buffer vb;
>> + spinlock_t lock;
> All locks require a comment to document what they protect. Same below.
>
>> + 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;
>> + struct mutex lock;
>> +
>> + struct {
>> + spinlock_t lock;
>> + struct list_head queue;
>> + } buffers;
>> +};
>> +
>> enum mali_c55_config_spaces {
>> MALI_C55_CONFIG_PING,
>> MALI_C55_CONFIG_PONG,
>> @@ -224,6 +247,7 @@ struct mali_c55 {
>> struct mali_c55_isp isp;
>> struct mali_c55_resizer resizers[MALI_C55_NUM_RZRS];
>> struct mali_c55_cap_dev cap_devs[MALI_C55_NUM_CAP_DEVS];
>> + struct mali_c55_stats stats;
>>
>> struct list_head contexts;
>> enum mali_c55_config_spaces next_config;
>> @@ -245,6 +269,8 @@ 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_ctx *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);
>> @@ -262,5 +288,7 @@ mali_c55_isp_fmt_next(const struct mali_c55_isp_fmt *fmt);
>> bool mali_c55_isp_is_format_supported(unsigned int mbus_code);
>> #define for_each_mali_isp_fmt(fmt)\
>> for ((fmt) = NULL; ((fmt) = mali_c55_isp_fmt_next((fmt)));)
>> +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 50caf5ee7474..9ea70010876c 100644
>> --- a/drivers/media/platform/arm/mali-c55/mali-c55-core.c
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-core.c
>> @@ -337,6 +337,16 @@ 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_3A,
>> + &mali_c55->stats.vdev.entity, 0,
>> + MEDIA_LNK_FL_ENABLED | MEDIA_LNK_FL_IMMUTABLE);
>> + if (ret) {
>> + dev_err(mali_c55->dev,
>> + "failed to link ISP and 3a stats node\n");
> s/3a stats/stats/
>
>> + goto err_remove_links;
>> + }
>> +
>> return 0;
>>
>> err_remove_links:
>> @@ -350,6 +360,7 @@ 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)
>> @@ -372,6 +383,10 @@ 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 ea8b7b866e7a..94876fba3353 100644
>> --- a/drivers/media/platform/arm/mali-c55/mali-c55-isp.c
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-isp.c
>> @@ -564,6 +564,7 @@ int mali_c55_register_isp(struct mali_c55 *mali_c55)
>> isp->pads[MALI_C55_ISP_PAD_SINK_VIDEO].flags = MEDIA_PAD_FL_SINK;
>> isp->pads[MALI_C55_ISP_PAD_SOURCE].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_3A].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 cb27abde2aa5..eb3719245ec3 100644
>> --- a/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
>> @@ -68,6 +68,9 @@
>> #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..aa40480ed814
>> --- /dev/null
>> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-stats.c
>> @@ -0,0 +1,350 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * ARM Mali-C55 ISP Driver - 3A Statistics capture device
>> + *
>> + * Copyright (C) 2023 Ideas on Board Oy
>> + */
>> +
>> +#include <linux/dmaengine.h>
>> +#include <linux/media/arm/mali-c55-config.h>
>> +#include <linux/spinlock.h>
> You're missing some headers here, for
>
> container_of()
> dev_err()
> list_*()
> mutex_init()
> strscpy()
> strscpy()
>
>> +
>> +#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 unsigned int metering_space_addrs[] = {
> const
>
>> + [MALI_C55_CONFIG_PING] = 0x095AC,
>> + [MALI_C55_CONFIG_PONG] = 0x2156C,
> Lower-case hex constants.
>
>> +};
>> +
>> +static int mali_c55_stats_enum_fmt_meta_cap(struct file *file, void *fh,
>> + struct v4l2_fmtdesc *f)
>> +{
>> + if (f->index || f->type != V4L2_BUF_TYPE_META_CAPTURE)
>> + return -EINVAL;
>> +
>> + f->pixelformat = V4L2_META_FMT_MALI_C55_3A_STATS;
> The format could be called V4L2_META_FMT_MALI_C55_STATS. While most
> statistics are related to one of the 3A algorithms, I think it would be
> better to name this generically. It's name bikeshedding only of course.
>
>> +
>> + 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_3A_STATS,
>> + .buffersize = sizeof(struct mali_c55_stats_buffer)
>> + };
>> +
>> + if (f->type != V4L2_BUF_TYPE_META_CAPTURE)
>> + return -EINVAL;
>> +
>> + 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;
>> + 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);
> Isn't the DMA completion handler run from IRQ context ? If so you'll need to use spin_lock_irq() here and in the other function that are not
> called with interrupts disabled.
They're run in the bottom half of the interrupt handler; I'm under the impression that that means
the interrupts aren't disabled, and it's safe to do...is that mistaken?
>
>> + list_add_tail(&buf->queue, &stats->buffers.queue);
>> + spin_unlock(&stats->buffers.lock);
>> +}
>> +
>> +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;
>> +
>> + 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);
>> +}
>> +
>> +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,
>> + .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;
>> +
>> + spin_lock(&buf->lock);
> I wonder if this is needed. Can the DMA engine call the completion
> handlers of two sequential DMA transfers in parallel ?
The DMA engine that's on the system we have can't...I wasn't sure whether that was generically true.
>
>> +
>> + if (buf->failed)
>> + goto out_unlock;
>> +
>> + buf->vb.vb2_buf.timestamp = ktime_get_boottime_ns();
>> +
>> + if (result->result != DMA_TRANS_NOERROR) {
>> + buf->failed = true;
>> + vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
> This will possibly return the buffer to userspace after the first DMA
> transfer. Userspace could then requeue the buffer to the kernel before
> the completion of the second DMA transfer. That will cause trouble. I
> think you should instead do something like
>
> spin_lock(&buf->lock);
>
> if (result->result != DMA_TRANS_NOERROR)
> buf->failed = true;
>
> if (!--buf->segments_remaining) {
> buf->vb.vb2_buf.timestamp = ktime_get_boottime_ns();
> vb2_buffer_done(&buf->vb.vb2_buf, buf->failed ?
> VB2_BUF_STATE_ERROR : VB2_BUF_STATE_DONE);
> }
>
> spin_unlock(&buf->lock);
>
> The
>
> buf->vb.vb2_buf.timestamp = ktime_get_boottime_ns();
>
> line could also be moved to mali_c55_stats_fill_buffer(), which would
> make sure the timestamp is filled in case of DMA submission failures.
Okedokey
>
>> + goto out_unlock;
>> + }
>> +
>> + if (!--buf->segments_remaining)
>> + vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_DONE);
>> +
>> +out_unlock:
>> + spin_unlock(&buf->lock);
>> +}
>> +
>> +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,
>> + void (*callback)(void *, const struct dmaengine_result *result))
> The same callback is used for both invocations of this function, you can
> drop the parameter and hardcode it below.
Yeah, not even sure now why I had a parameter.
>> +{
>> + 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 = callback;
>> + 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_ctx *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;
>> + 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;
>> +
>> + /*
>> + * There are infact two noncontiguous sections of the ISP's
> s/infact/in fact/
>
>> + * memory space that hold statistics for 3a algorithms to use. A
> s/use. A/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,
>> + mali_c55_stats_metering_complete);
>> + if (ret)
>> + goto err_fail_buffer;
>> +
>> + src = ctx->base + metering_space_addrs[cfg_space];
>> + dst += MALI_C55_1024BIN_HIST_SIZE;
>> +
>> + ret = mali_c55_stats_dma_xfer(
>> + stats, src, dst, buf,
>> + sizeof(struct mali_c55_stats_buffer) - MALI_C55_1024BIN_HIST_SIZE,
>> + mali_c55_stats_metering_complete);
>> + if (ret) {
>> + dmaengine_terminate_sync(stats->channel);
>> + goto err_fail_buffer;
>> + }
> I think you will need to terminate DMA transfers at stream off time.
>
>> +
>> + 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);
> Do we need a CPU fallback in case no DMA is available ?
Yes, actually.
>
> I'm still very curious to know how long it takes to perform the DMA
> transfer, compared to copying the data with the CPU, and especially
> compared to the frame duration.
On my list of things to test and report :)
>
>> + 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 = mali_c55->dev;
> That's not the right device. The device that performs the DMA operation
> is the DMA engine, and that's what you need to pass to vb2. Otherwise
> the DMA address returned by vb2_dma_contig_plane_dma_addr() will be
> mapped to the ISP device, not the DMA engine. In practice, if neither
> are behind an IOMMU, things will likely work, but when that's not the
> case, run into problems.
>
>> +
>> + 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));
> s/3a //
>
>> + vdev->release = video_device_release_empty;
> That's never right. You should refcount the data structures to ensure
> proper lifetime management.
>
>> + 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;
>> +}
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