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

[Brian Starkey <brian.starkey@arm.com>]

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.

>+		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.

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
>