[PATCH v5 10/16] media: platform: Add mali-c55 3a stats devnode
Dan Scally
dan.scally at ideasonboard.com
Tue Jul 2 00:00:27 PDT 2024
Morning Laurent
On 01/07/2024 16:12, Dan Scally wrote:
> Hi Laurent
>
> On 29/06/2024 16:04, Laurent Pinchart wrote:
>> Hi Dan,
>>
>> On Thu, Jun 20, 2024 at 04:10:01PM +0100, Daniel Scally wrote:
>>> On 16/06/2024 22:19, Laurent Pinchart wrote:
>>>> 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?
>> I'm talking about the DMA completion handler, called by the DMA engine
>> subsystem, not the IRQs of the C55 itself.
>
>
> Ah! I follow you now sorry. Hm, that's an interesting thought...I think for the PL330 the answer
> is no; the interrupt handler wakes a thread that runs the callbacks for any DMA transfers that are
> completed...I don't know that that's a design rule we can rely on though so possibly it's better
> to be safe. Is there a disadvantage to using spin_lock_irq() outside of IRQ context?
Actually I think from [1] that the answer is they're not run from interrupt context, the page says
"Note that callbacks will always be invoked from the DMA engine's tasklet, never from interrupt
context".
[1] Documentation/driver-api/dmaengine/client.rst
>
>>
>>>>> + 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.
>> I think it is, but please double-check.
>>
>>>>> +
>>>>> + 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 :)
>> Looking forward to it :-)
>>
>>>>> + 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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