Re: [PATCH v5 1/4] drm/fence: add in-fences support

From: Daniel Vetter
Date: Fri Oct 21 2016 - 08:51:36 EST

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On Thu, Oct 20, 2016 at 12:50:02PM -0200, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
>
> There is now a new property called FENCE_FD attached to every plane
> state that receives the sync_file fd from userspace via the atomic commit
> IOCTL.
>
> The fd is then translated to a fence (that may be a fence_collection
> 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
>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>

Since you rename plane_state->fence to in_fence (why exactly?) this breaks
compilation for imx and msm. Also there's the question of which fence
should win, if there's both explicit and implicit fences. I think the best
way to solve that is by adding a helper to set the implicit fence, which
drivers are supposed to call. That helper only sets the fence if there's
not yet an explicit fence attached. New sequence would be:

- patch1: roll out that helper (e.g. drm_atomic_plane_state_set_fence or
whatever) for all drivers using it.
- patch2 (this one here): add explicit fences and change the helper to
cooporate correctly.

> ---
> drivers/gpu/drm/Kconfig | 1 +
> drivers/gpu/drm/drm_atomic.c | 14 ++++++++++++++
> drivers/gpu/drm/drm_atomic_helper.c | 13 +++++++------
> drivers/gpu/drm/drm_crtc.c | 6 ++++++
> drivers/gpu/drm/drm_plane.c | 1 +
> include/drm/drm_crtc.h | 5 +++++
> include/drm/drm_plane.h | 4 ++--
> 7 files changed, 36 insertions(+), 8 deletions(-)
>
> 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 5dd7054..b3284b2 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->in_fence)
> + fence_put(state->in_fence);
> +
> + state->in_fence = sync_file_get_fence(val);
> + if (!state->in_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);
> @@ -745,6 +757,8 @@ 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 07b432f..73464b1 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1031,22 +1031,20 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
> if (!pre_swap)
> plane_state = plane->state;
>
> - if (!plane_state->fence)
> + if (!plane_state->in_fence)
> continue;
>
> - WARN_ON(!plane_state->fb);
> -
> /*
> * If waiting for fences pre-swap (ie: nonblock), userspace can
> * still interrupt the operation. Instead of blocking until the
> * timer expires, make the wait interruptible.
> */
> - ret = fence_wait(plane_state->fence, pre_swap);
> + ret = fence_wait(plane_state->in_fence, pre_swap);
> if (ret)
> return ret;
>
> - fence_put(plane_state->fence);
> - plane_state->fence = NULL;
> + fence_put(plane_state->in_fence);
> + plane_state->in_fence = NULL;
> }
>
> return 0;
> @@ -3114,6 +3112,9 @@ void __drm_atomic_helper_plane_destroy_state(struct drm_plane_state *state)
> {
> if (state->fb)
> drm_framebuffer_unreference(state->fb);
> +
> + if (state->in_fence)
> + fence_put(state->in_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 60403bf..fcb6453 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 284c1b3..279132e 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1206,6 +1206,11 @@ 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.
> */
> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> index 0235390..3cb9bf1 100644
> --- a/include/drm/drm_plane.h
> +++ b/include/drm/drm_plane.h
> @@ -34,7 +34,7 @@ struct drm_crtc;
> * @plane: backpointer to the plane
> * @crtc: currently bound CRTC, NULL if disabled
> * @fb: currently bound framebuffer
> - * @fence: optional fence to wait for before scanning out @fb
> + * @in_fence: optional fence to wait for before scanning out @fb
> * @crtc_x: left position of visible portion of plane on crtc
> * @crtc_y: upper position of visible portion of plane on crtc
> * @crtc_w: width of visible portion of plane on crtc
> @@ -59,7 +59,7 @@ struct drm_plane_state {
>
> struct drm_crtc *crtc; /* do not write directly, use drm_atomic_set_crtc_for_plane() */
> struct drm_framebuffer *fb; /* do not write directly, use drm_atomic_set_fb_for_plane() */
> - struct fence *fence;
> + struct fence *in_fence;

I think it'd be good to move the kerneldoc into an in-line comment here
and expand a bit upon the expected semantics. This is a pretty important
part of the atomic uabi!

Otherwise looks all good.
-Daniel

>
> /* Signed dest location allows it to be partially off screen */
> int32_t crtc_x, crtc_y;
> --
> 2.5.5
>

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

Next message: Tetsuo Handa: "[PATCH 2/8] CaitSith: Add pathname calculation functions."
Previous message: Petr Mladek: "[PATCH 2/2] kdb: Call vkdb_printf() from vprintk_default() only when wanted"
In reply to: Gustavo Padovan: "[PATCH v5 1/4] drm/fence: add in-fences support"
Next in thread: Daniel Vetter: "Re: [PATCH v5 0/4] drm: add explicit fencing"
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