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

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Nov 08, 2016 at 03:27:14PM +0000, Brian Starkey wrote:
> Hi Gustavo,
> 
> 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;
> > +
> 
> Sorry, I'm a bit late to bring this up but what's the expected
> behaviour of a commit which sets OUT_FENCE twice (first with a valid
> fence, then with -1 later in the list)? Maybe you need to actually
> clear state->fence for -1.

Good point, we should probaly reject that. Since ->fence should autoclear
(I totally missed that one) we should check for an existing fence and fail
if it's set already.

> > +		if (state->fence)
> > +			dma_fence_put(state->fence);
> > +
> > +		state->fence = sync_file_get_fence(val);
> > +		if (!state->fence)
> > +			return -EINVAL;
> > +
> > 	} 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);
> > 
> 
> It looks like you need to add something in
> __drm_atomic_helper_plane_duplicate_state() to either get a reference
> on the fence or set state->fence = NULL, because the memcpy() there
> will copy the pointer.

Clearing to NULL would be best, since that matches the meaning of the -1
we return to userspace when reading the property. I guess I get to retract
my r-b.
-Daniel

> 
> Cheers,
> -Brian
> 
> > 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