Re: [RFC 8/8] drm/fence: add out-fences support

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Apr 14, 2016 at 06:29:41PM -0700, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> 
> Support DRM out-fences creating a sync_file with a fence for each crtc
> update with the DRM_MODE_ATOMIC_OUT_FENCE flag.
> 
> We then send an struct drm_out_fences array with the out-fences fds back in
> the drm_atomic_ioctl() as an out arg in the out_fences_ptr field.
> 
> struct drm_out_fences {
> 	__u32   crtc_id;
> 	__u32   fd;
> };
> 
> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> ---
>  drivers/gpu/drm/drm_atomic.c        | 109 +++++++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/drm_atomic_helper.c |   1 +
>  include/drm/drm_crtc.h              |   3 +
>  include/uapi/drm/drm_mode.h         |   7 +++
>  4 files changed, 119 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 0b95526..af6e051 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1560,6 +1560,103 @@ void drm_atomic_clean_old_fb(struct drm_device *dev,
>  }
>  EXPORT_SYMBOL(drm_atomic_clean_old_fb);
>  
> +static int drm_atomic_get_out_fences(struct drm_device *dev,
> +				     struct drm_atomic_state *state,
> +				     uint32_t __user *out_fences_ptr,
> +				     uint64_t count_out_fences,
> +				     uint64_t user_data)
> +{
> +	struct drm_crtc *crtc;
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_out_fences *out_fences;
> +	struct sync_file **sync_file;
> +	int num_fences = 0;
> +	int i, ret;
> +
> +	out_fences = kcalloc(count_out_fences, sizeof(*out_fences),
> +			     GFP_KERNEL);
> +	if (!out_fences)
> +		return -ENOMEM;
> +
> +	sync_file = kcalloc(count_out_fences, sizeof(*sync_file),
> +			     GFP_KERNEL);
> +	if (!sync_file) {
> +		kfree(out_fences);
> +		return -ENOMEM;
> +	}
> +
> +	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +		struct drm_pending_vblank_event *e;
> +		struct fence *fence;
> +		char name[32];
> +		int fd;
> +
> +		fence = sync_timeline_create_fence(crtc->timeline,
> +						   crtc->fence_seqno);
> +		if (!fence) {
> +			ret = -ENOMEM;
> +			goto out;
> +		}
> +
> +		snprintf(name, sizeof(name), "crtc-%d_%lu",
> +			 drm_crtc_index(crtc), crtc->fence_seqno++);
> +
> +		sync_file[i] = sync_file_create(name, fence);
> +		if(!sync_file[i]) {
> +			ret = -ENOMEM;
> +			goto out;
> +		}
> +
> +		fd = get_unused_fd_flags(O_CLOEXEC);
> +		if (fd < 0) {
> +			ret = fd;
> +			goto out;
> +		}
> +
> +		sync_file_install(sync_file[i], fd);
> +
> +		if (crtc_state->event) {
> +			crtc_state->event->base.fence = fence;
> +		} else {
> +			e = create_vblank_event(dev, NULL, fence, user_data);
> +			if (!e) {
> +				put_unused_fd(fd);
> +				ret = -ENOMEM;
> +				goto out;
> +			}
> +
> +			crtc_state->event = e;
> +		}
> +		if (num_fences > count_out_fences) {
> +			put_unused_fd(fd);
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +
> +		fence_get(fence);
> +
> +		out_fences[num_fences].crtc_id = crtc->base.id;
> +		out_fences[num_fences].fd = fd;
> +		num_fences++;
> +	}
> +
> +	if (copy_to_user(out_fences_ptr, out_fences,
> +			 num_fences * sizeof(*out_fences))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	return 0;
> +
> +out:
> +	for (i = 0 ; i < count_out_fences ; i++) {
> +		if (sync_file[i])
> +			sync_file_put(sync_file[i]);
> +	}
> +
> +	return ret;
> +}
> +
>  int drm_mode_atomic_ioctl(struct drm_device *dev,
>  			  void *data, struct drm_file *file_priv)
>  {
> @@ -1568,6 +1665,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  	uint32_t __user *count_props_ptr = (uint32_t __user *)(unsigned long)(arg->count_props_ptr);
>  	uint32_t __user *props_ptr = (uint32_t __user *)(unsigned long)(arg->props_ptr);
>  	uint64_t __user *prop_values_ptr = (uint64_t __user *)(unsigned long)(arg->prop_values_ptr);
> +	uint32_t __user *out_fences_ptr = (uint32_t __user *)(unsigned long)(arg->out_fences_ptr);
>  	unsigned int copied_objs, copied_props;
>  	struct drm_atomic_state *state;
>  	struct drm_modeset_acquire_ctx ctx;
> @@ -1601,7 +1699,8 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  
>  	/* can't test and expect an event at the same time. */
>  	if ((arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) &&
> -			(arg->flags & DRM_MODE_PAGE_FLIP_EVENT))
> +			(arg->flags & (DRM_MODE_PAGE_FLIP_EVENT
> +			 | DRM_MODE_ATOMIC_OUT_FENCE)))
>  		return -EINVAL;
>  
>  	drm_modeset_acquire_init(&ctx, 0);
> @@ -1693,6 +1792,14 @@ retry:
>  		}
>  	}
>  
> +	if (arg->flags & DRM_MODE_ATOMIC_OUT_FENCE) {

OUT_FENCE and TEST_ONLY probably don't make sense, and need to be
rejected. Needs a testcase, too.

> +		ret = drm_atomic_get_out_fences(dev, state, out_fences_ptr,
> +						arg->count_out_fences,
> +						arg->user_data);
> +		if (ret < 0)
> +			goto out;
> +	}
> +
>  	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {

If anything fails below this point we need to clean up the sync_file/fd
mess. Might be easier to first create sync_file objects only, and only
install the fd once atomic has succeeded. You probably want to reserve the
fd slots beforehand though.

That means a bunch more per-crtc state in drm_atomic_state. We should
probably take all the per-crtc pointers and throw them into a small
struct, to avoid allocating individual arrays for everything. So

struct drm_atomic_state_per_crtc {
	struct drm_crtc *crtc;
	struct drm_crtc_state *state;
	struct sync_file *sync_file;
	int fd;
};

Sorry if this means a bit a sprawling upfront refactor :(

Wrt testcase: Need evil ones that pass invalid pointer to out_fences_ptr
or too small array size in count_out_fences and all that ofc.
-Daniel

>  		/*
>  		 * Unlike commit, check_only does not clean up state.
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 6ed8339..15ba3a8 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -31,6 +31,7 @@
>  #include <drm/drm_crtc_helper.h>
>  #include <drm/drm_atomic_helper.h>
>  #include <linux/fence.h>
> +#include <linux/sync_file.h>
>  
>  /**
>   * DOC: overview
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 7934178..53e4e71 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -717,6 +717,7 @@ struct drm_crtc_funcs {
>   * @properties: property tracking for this CRTC
>   * @state: current atomic state for this CRTC
>   * @timeline: sync timeline for fence sigalling
> + * @fence_seqno: seqno variable to create fences
>   * @acquire_ctx: per-CRTC implicit acquire context used by atomic drivers for
>   * 	legacy IOCTLs
>   *
> @@ -773,7 +774,9 @@ struct drm_crtc {
>  
>  	struct drm_crtc_state *state;
>  
> +	/* for out-fences */
>  	struct sync_timeline *timeline;
> +	unsigned long fence_seqno;
>  
>  	/*
>  	 * For legacy crtc IOCTLs so that atomic drivers can get at the locking
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 39905cc..4cdcd22 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -592,6 +592,11 @@ struct drm_mode_destroy_dumb {
>  		DRM_MODE_ATOMIC_ALLOW_MODESET |\
>  		DRM_MODE_ATOMIC_OUT_FENCE)
>  
> +struct drm_out_fences {
> +	__u32	crtc_id;
> +	__u32	fd;
> +};
> +
>  struct drm_mode_atomic {
>  	__u32 flags;
>  	__u32 count_objs;
> @@ -601,6 +606,8 @@ struct drm_mode_atomic {
>  	__u64 prop_values_ptr;
>  	__u64 reserved;
>  	__u64 user_data;
> +	__u64 count_out_fences;
> +	__u64 out_fences_ptr;
>  };
>  
>  /**
> -- 
> 2.5.5
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch