2017-11-17 Mauro Carvalho Chehab <[email protected]>:
> Em Wed, 15 Nov 2017 15:10:53 -0200
> Gustavo Padovan <[email protected]> escreveu:
>
> > From: Gustavo Padovan <[email protected]>
> >
> > Receive in-fence from userspace and add support for waiting on them
> > before queueing the buffer to the driver. Buffers can't be queued to the
> > driver before its fences signal. And a buffer can't be queue to the driver
> > out of the order they were queued from userspace. That means that even if
> > it fence signal it must wait all other buffers, ahead of it in the queue,
> > to signal first.
> >
> > To make that possible we use fence_array to keep that ordering. Basically
> > we create a fence_array that contains both the current fence and the fence
> > from the previous buffer (which might be a fence array as well). The base
> > fence class for the fence_array becomes the new buffer fence, waiting on
> > that one guarantees that it won't be queued out of order.
> >
> > v6:
> > - With fences always keep the order userspace queues the buffers.
> > - Protect in_fence manipulation with a lock (Brian Starkey)
> > - check if fences have the same context before adding a fence array
> > - Fix last_fence ref unbalance in __set_in_fence() (Brian Starkey)
> > - Clean up fence if __set_in_fence() fails (Brian Starkey)
> > - treat -EINVAL from dma_fence_add_callback() (Brian Starkey)
> >
> > v5: - use fence_array to keep buffers ordered in vb2 core when
> > needed (Brian Starkey)
> > - keep backward compat on the reserved2 field (Brian Starkey)
> > - protect fence callback removal with lock (Brian Starkey)
> >
> > v4:
> > - Add a comment about dma_fence_add_callback() not returning a
> > error (Hans)
> > - Call dma_fence_put(vb->in_fence) if fence signaled (Hans)
> > - select SYNC_FILE under config VIDEOBUF2_CORE (Hans)
> > - Move dma_fence_is_signaled() check to __enqueue_in_driver() (Hans)
> > - Remove list_for_each_entry() in __vb2_core_qbuf() (Hans)
> > - Remove if (vb->state != VB2_BUF_STATE_QUEUED) from
> > vb2_start_streaming() (Hans)
> > - set IN_FENCE flags on __fill_v4l2_buffer (Hans)
> > - Queue buffers to the driver as soon as they are ready (Hans)
> > - call fill_user_buffer() after queuing the buffer (Hans)
> > - add err: label to clean up fence
> > - add dma_fence_wait() before calling vb2_start_streaming()
> >
> > v3: - document fence parameter
> > - remove ternary if at vb2_qbuf() return (Mauro)
> > - do not change if conditions behaviour (Mauro)
> >
> > v2:
> > - fix vb2_queue_or_prepare_buf() ret check
> > - remove check for VB2_MEMORY_DMABUF only (Javier)
> > - check num of ready buffers to start streaming
> > - when queueing, start from the first ready buffer
> > - handle queue cancel
> >
> > Signed-off-by: Gustavo Padovan <[email protected]>
> > ---
> > drivers/media/v4l2-core/Kconfig | 1 +
> > drivers/media/v4l2-core/videobuf2-core.c | 202 ++++++++++++++++++++++++++++---
> > drivers/media/v4l2-core/videobuf2-v4l2.c | 29 ++++-
> > include/media/videobuf2-core.h | 17 ++-
> > 4 files changed, 231 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/Kconfig b/drivers/media/v4l2-core/Kconfig
> > index a35c33686abf..3f988c407c80 100644
> > --- a/drivers/media/v4l2-core/Kconfig
> > +++ b/drivers/media/v4l2-core/Kconfig
> > @@ -83,6 +83,7 @@ config VIDEOBUF_DVB
> > # Used by drivers that need Videobuf2 modules
> > config VIDEOBUF2_CORE
> > select DMA_SHARED_BUFFER
> > + select SYNC_FILE
> > tristate
> >
> > config VIDEOBUF2_MEMOPS
> > diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> > index 60f8b582396a..26de4c80717d 100644
> > --- a/drivers/media/v4l2-core/videobuf2-core.c
> > +++ b/drivers/media/v4l2-core/videobuf2-core.c
> > @@ -23,6 +23,7 @@
> > #include <linux/sched.h>
> > #include <linux/freezer.h>
> > #include <linux/kthread.h>
> > +#include <linux/dma-fence-array.h>
> >
> > #include <media/videobuf2-core.h>
> > #include <media/v4l2-mc.h>
> > @@ -346,6 +347,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
> > vb->index = q->num_buffers + buffer;
> > vb->type = q->type;
> > vb->memory = memory;
> > + spin_lock_init(&vb->fence_cb_lock);
> > for (plane = 0; plane < num_planes; ++plane) {
> > vb->planes[plane].length = plane_sizes[plane];
> > vb->planes[plane].min_length = plane_sizes[plane];
> > @@ -1222,6 +1224,9 @@ static void __enqueue_in_driver(struct vb2_buffer *vb)
> > {
> > struct vb2_queue *q = vb->vb2_queue;
> >
> > + if (vb->in_fence && !dma_fence_is_signaled(vb->in_fence))
> > + return;
> > +
> > vb->state = VB2_BUF_STATE_ACTIVE;
> > atomic_inc(&q->owned_by_drv_count);
> >
> > @@ -1273,6 +1278,23 @@ static int __buf_prepare(struct vb2_buffer *vb, const void *pb)
> > return 0;
> > }
> >
> > +static int __get_num_ready_buffers(struct vb2_queue *q)
> > +{
> > + struct vb2_buffer *vb;
> > + int ready_count = 0;
> > + unsigned long flags;
> > +
> > + /* count num of buffers ready in front of the queued_list */
> > + list_for_each_entry(vb, &q->queued_list, queued_entry) {
> > + spin_lock_irqsave(&vb->fence_cb_lock, flags);
> > + if (!vb->in_fence || dma_fence_is_signaled(vb->in_fence))
> > + ready_count++;
> > + spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
> > + }
> > +
> > + return ready_count;
> > +}
> > +
> > int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
> > {
> > struct vb2_buffer *vb;
> > @@ -1361,9 +1383,87 @@ static int vb2_start_streaming(struct vb2_queue *q)
> > return ret;
> > }
> >
> > -int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
> > +static struct dma_fence *__set_in_fence(struct vb2_queue *q,
> > + struct vb2_buffer *vb,
> > + struct dma_fence *fence)
> > +{
> > + if (q->last_fence && dma_fence_is_signaled(q->last_fence)) {
> > + dma_fence_put(q->last_fence);
> > + q->last_fence = NULL;
> > + }
> > +
> > + /*
> > + * We always guarantee the ordering of buffers queued from
> > + * userspace to be the same it is queued to the driver. For that
> > + * we create a fence array with the fence from the last queued
> > + * buffer and this one, that way the fence for this buffer can't
> > + * signal before the last one.
> > + */
> > + if (fence && q->last_fence) {
> > + struct dma_fence **fences;
> > + struct dma_fence_array *arr;
> > +
> > + if (fence->context == q->last_fence->context) {
> > + if (fence->seqno - q->last_fence->seqno <= INT_MAX) {
> > + dma_fence_put(q->last_fence);
> > + q->last_fence = dma_fence_get(fence);
> > + } else {
> > + dma_fence_put(fence);
> > + fence = dma_fence_get(q->last_fence);
> > + }
> > + return fence;
> > + }
> > +
> > + fences = kcalloc(2, sizeof(*fences), GFP_KERNEL);
> > + if (!fences)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + fences[0] = fence;
> > + fences[1] = q->last_fence;
> > +
> > + arr = dma_fence_array_create(2, fences,
> > + dma_fence_context_alloc(1),
> > + 1, false);
> > + if (!arr) {
> > + kfree(fences);
> > + return ERR_PTR(-ENOMEM);
> > + }
> > +
> > + fence = &arr->base;
> > +
> > + q->last_fence = dma_fence_get(fence);
> > + } else if (!fence && q->last_fence) {
> > + fence = dma_fence_get(q->last_fence);
> > + }
> > +
> > + return fence;
> > +}
> > +
> > +static void vb2_qbuf_fence_cb(struct dma_fence *f, struct dma_fence_cb *cb)
> > +{
> > + struct vb2_buffer *vb = container_of(cb, struct vb2_buffer, fence_cb);
> > + struct vb2_queue *q = vb->vb2_queue;
> > + unsigned long flags;
> > +
> > + spin_lock_irqsave(&vb->fence_cb_lock, flags);
> > + if (!vb->in_fence) {
> > + spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
> > + return;
> > + }
> > +
> > + dma_fence_put(vb->in_fence);
> > + vb->in_fence = NULL;
> > +
> > + if (q->start_streaming_called)
> > + __enqueue_in_driver(vb);
> > + spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
> > +}
> > +
> > +int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
> > + struct dma_fence *fence)
> > {
> > struct vb2_buffer *vb;
> > + unsigned long flags;
> > int ret;
> >
> > vb = q->bufs[index];
> > @@ -1372,16 +1472,18 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
> > case VB2_BUF_STATE_DEQUEUED:
> > ret = __buf_prepare(vb, pb);
> > if (ret)
> > - return ret;
> > + goto err;
> > break;
> > case VB2_BUF_STATE_PREPARED:
> > break;
> > case VB2_BUF_STATE_PREPARING:
> > dprintk(1, "buffer still being prepared\n");
> > - return -EINVAL;
> > + ret = -EINVAL;
> > + goto err;
> > default:
> > dprintk(1, "invalid buffer state %d\n", vb->state);
> > - return -EINVAL;
> > + ret = -EINVAL;
> > + goto err;
> > }
> >
> > /*
> > @@ -1398,30 +1500,83 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
> >
> > trace_vb2_qbuf(q, vb);
> >
> > + vb->in_fence = __set_in_fence(q, vb, fence);
> > + if (IS_ERR(vb->in_fence)) {
> > + dma_fence_put(fence);
> > + ret = PTR_ERR(vb->in_fence);
> > + goto err;
> > + }
> > + fence = NULL;
> > +
> > + /*
> > + * If it is time to call vb2_start_streaming() wait for the fence
> > + * to signal first. Of course, this happens only once per streaming.
> > + * We want to run any step that might fail before we set the callback
> > + * to queue the fence when it signals.
> > + */
> > + if (vb->in_fence && !q->start_streaming_called &&
> > + __get_num_ready_buffers(q) == q->min_buffers_needed - 1)
> > + dma_fence_wait(vb->in_fence, true);
> > +
>
> The above code sounds weird: it is called even if the user is not
> using fences.
>
> You should probably be doing something like:
>
> if (fence || q->last_fence) {
> vb->in_fence = __set_in_fence(q, vb, fence);
> ...
> }
>
Sure.
> > /*
> > * If streamon has been called, and we haven't yet called
> > * start_streaming() since not enough buffers were queued, and
> > * we now have reached the minimum number of queued buffers,
> > * then we can finally call start_streaming().
> > - *
> > - * If already streaming, give the buffer to driver for processing.
> > - * If not, the buffer will be given to driver on next streamon.
> > */
> > if (q->streaming && !q->start_streaming_called &&
> > - q->queued_count >= q->min_buffers_needed) {
> > + __get_num_ready_buffers(q) >= q->min_buffers_needed) {
>
> I guess the case where fences is not used is not covered here.
>
> You probably should add a check at __get_num_ready_buffers(q)
> as well, making it just return q->queued_count if fences isn't
> used.
We can't know that beforehand, some buffer ahead may have a fence,
but there is already a check for !fence for each buffer. If none of
them have fences the return will be equal to q->queued_count.
Gustavo
From 1584351318606855380@xxx Fri Nov 17 21:46:00 +0000 2017
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Em Fri, 17 Nov 2017 11:12:48 -0200
Gustavo Padovan <[email protected]> escreveu:
> > > /*
> > > * If streamon has been called, and we haven't yet called
> > > * start_streaming() since not enough buffers were queued, and
> > > * we now have reached the minimum number of queued buffers,
> > > * then we can finally call start_streaming().
> > > - *
> > > - * If already streaming, give the buffer to driver for processing.
> > > - * If not, the buffer will be given to driver on next streamon.
> > > */
> > > if (q->streaming && !q->start_streaming_called &&
> > > - q->queued_count >= q->min_buffers_needed) {
> > > + __get_num_ready_buffers(q) >= q->min_buffers_needed) {
> >
> > I guess the case where fences is not used is not covered here.
> >
> > You probably should add a check at __get_num_ready_buffers(q)
> > as well, making it just return q->queued_count if fences isn't
> > used.
>
> We can't know that beforehand, some buffer ahead may have a fence,
> but there is already a check for !fence for each buffer. If none of
> them have fences the return will be equal to q->queued_count.
Hmm... are we willing to support the case where just some
buffers have fences? Why?
In any case, we should add a notice at the documentation telling
about what happens if not all buffers have fences, and if fences
are required to be setup before starting streaming, or if it is
possible to dynamically change the fances behavior while streaming.
--
Thanks,
Mauro
From 1584340618310018009@xxx Fri Nov 17 18:55:56 +0000 2017
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