Re: [PATCH v7 1/3] drm/fence: add in-fences support

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Nov 08, 2016 at 03:54:48PM +0900, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> 
> There is now a new property called IN_FENCE_FD attached to every plane
> state that receives sync_file fds from userspace via the atomic commit
> IOCTL.
> 
> The fd is then translated to a fence (that may be a fence_array
> subclass or just a normal fence) and then used by DRM to fence_wait() for
> all fences in the sync_file to signal. So it only commits when all
> framebuffers are ready to scanout.
> 
> v2: Comments by Daniel Vetter:
> 	- remove set state->fence = NULL in destroy phase
> 	- accept fence -1 as valid and just return 0
> 	- do not call fence_get() - sync_file_fences_get() already calls it
> 	- fence_put() if state->fence is already set, in case userspace
> 	set the property more than once.
> 
> v3: WARN_ON if fence is set but state has no FB
> 
> v4: Comment from Maarten Lankhorst
> 	- allow set fence with no related fb
> 
> v5: rename FENCE_FD to IN_FENCE_FD
> 
> v6: Comments by Daniel Vetter:
> 	- rename plane_state->in_fence back to "fence"
> 	- re-introduce WARN_ON if fence set but no fb
> 
>      - rebase after fence -> dma_fence rename
> 
> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> ---
>  drivers/gpu/drm/Kconfig             |  1 +
>  drivers/gpu/drm/drm_atomic.c        | 14 ++++++++++++++
>  drivers/gpu/drm/drm_atomic_helper.c |  3 +++
>  drivers/gpu/drm/drm_crtc.c          |  6 ++++++
>  drivers/gpu/drm/drm_plane.c         |  1 +
>  include/drm/drm_crtc.h              |  5 +++++
>  6 files changed, 30 insertions(+)
> 
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 483059a..43cb33d 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -12,6 +12,7 @@ menuconfig DRM
>  	select I2C
>  	select I2C_ALGOBIT
>  	select DMA_SHARED_BUFFER
> +	select SYNC_FILE
>  	help
>  	  Kernel-level support for the Direct Rendering Infrastructure (DRI)
>  	  introduced in XFree86 4.0. If you say Y here, you need to select
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 5e73954..d1ae463 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -30,6 +30,7 @@
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_mode.h>
>  #include <drm/drm_plane_helper.h>
> +#include <linux/sync_file.h>
>  
>  #include "drm_crtc_internal.h"
>  
> @@ -686,6 +687,17 @@ int drm_atomic_plane_set_property(struct drm_plane *plane,
>  		drm_atomic_set_fb_for_plane(state, fb);
>  		if (fb)
>  			drm_framebuffer_unreference(fb);
> +	} else if (property == config->prop_in_fence_fd) {
> +		if (U642I64(val) == -1)
> +			return 0;
> +
> +		if (state->fence)
> +			dma_fence_put(state->fence);
> +
> +		state->fence = sync_file_get_fence(val);
> +		if (!state->fence)
> +			return -EINVAL;

Might have missed it, but your igt only seems to test for -1 (i.e. no
fence), not for an entirely invalid fence. I think we need another
testcase which opens some file (/dev/null maybe) and tries to use that as
fence.

Another corner case is error unrolling. I think we need 3 cases for full
coverage:
- Early error unrolling while setting properties. Best way imo would be 1)
  set an in-fence (correctly), then 2) set an invalid property (just set
  the CRTC plane property to something invalid like ~0ULL).
- Late unrolling (i.e. atomic_check fails). I think the reliable way here
  to provoke this on all drivers would be: Atomic commit with in-fence and
  otherwise everything the same (i.e. known to work), but changing the
  crtc's ACTIVE property from false to true without setting ALLOW_MODESET.
- And then also a successful TEST_ONLY commit.

Same is required for out-fences ofc too.

Patch itself looks good, and I couldn't poke any holes into it.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> +
>  	} else if (property == config->prop_crtc_id) {
>  		struct drm_crtc *crtc = drm_crtc_find(dev, val);
>  		return drm_atomic_set_crtc_for_plane(state, crtc);
> @@ -747,6 +759,8 @@ drm_atomic_plane_get_property(struct drm_plane *plane,
>  
>  	if (property == config->prop_fb_id) {
>  		*val = (state->fb) ? state->fb->base.id : 0;
> +	} else if (property == config->prop_in_fence_fd) {
> +		*val = -1;
>  	} else if (property == config->prop_crtc_id) {
>  		*val = (state->crtc) ? state->crtc->base.id : 0;
>  	} else if (property == config->prop_crtc_x) {
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 75ad01d..26a067f 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -3114,6 +3114,9 @@ void __drm_atomic_helper_plane_destroy_state(struct drm_plane_state *state)
>  {
>  	if (state->fb)
>  		drm_framebuffer_unreference(state->fb);
> +
> +	if (state->fence)
> +		dma_fence_put(state->fence);
>  }
>  EXPORT_SYMBOL(__drm_atomic_helper_plane_destroy_state);
>  
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 13441e2..7878bfd 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -397,6 +397,12 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
>  		return -ENOMEM;
>  	dev->mode_config.prop_fb_id = prop;
>  
> +	prop = drm_property_create_signed_range(dev, DRM_MODE_PROP_ATOMIC,
> +			"IN_FENCE_FD", -1, INT_MAX);
> +	if (!prop)
> +		return -ENOMEM;
> +	dev->mode_config.prop_in_fence_fd = prop;
> +
>  	prop = drm_property_create_object(dev, DRM_MODE_PROP_ATOMIC,
>  			"CRTC_ID", DRM_MODE_OBJECT_CRTC);
>  	if (!prop)
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 249c0ae..3957ef8 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -137,6 +137,7 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
>  
>  	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
>  		drm_object_attach_property(&plane->base, config->prop_fb_id, 0);
> +		drm_object_attach_property(&plane->base, config->prop_in_fence_fd, -1);
>  		drm_object_attach_property(&plane->base, config->prop_crtc_id, 0);
>  		drm_object_attach_property(&plane->base, config->prop_crtc_x, 0);
>  		drm_object_attach_property(&plane->base, config->prop_crtc_y, 0);
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index fa1aa21..719b6a8 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1201,6 +1201,11 @@ struct drm_mode_config {
>  	 */
>  	struct drm_property *prop_fb_id;
>  	/**
> +	 * @prop_in_fence_fd: Sync File fd representing the incoming fences
> +	 * for a Plane.
> +	 */
> +	struct drm_property *prop_in_fence_fd;
> +	/**
>  	 * @prop_crtc_id: Default atomic plane property to specify the
>  	 * &drm_crtc.
>  	 */
> -- 
> 2.5.5
> 

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