Message-ID: <20161114145720.GB24412@e106950-lin.cambridge.arm.com>
Date:   Mon, 14 Nov 2016 14:57:21 +0000
From:   Brian Starkey <brian.starkey@....com>
To:     Gustavo Padovan <gustavo@...ovan.org>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Daniel Stone <daniels@...labora.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Rob Clark <robdclark@...il.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        John Harrison <John.C.Harrison@...el.com>,
        laurent.pinchart@...asonboard.com, seanpaul@...gle.com,
        marcheu@...gle.com, m.chehab@...sung.com,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
        ville.syrjala@...ux.intel.com
Subject: Re: [PATCH v10 3/3] drm/fence: add out-fences support

Hi Gustavo,

I was just writing some internal docs, and it occurred to me that the
out-fence implementation here doesn't seem to match what we discussed
with Ville a few weeks back (which had completely slipped my mind).

Did the idea of returning -1 fences for multiple commits within a
frame get dropped? I didn't see any discussion further than that
thread on v5 from October:
http://lkml.iu.edu/hypermail/linux/kernel/1610.2/04727.html

Cheers,
Brian

On Mon, Nov 14, 2016 at 10:59:56AM +0900, Gustavo Padovan wrote:
>From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
>
>Support DRM out-fences by creating a sync_file with a fence for each CRTC
>that sets the OUT_FENCE_PTR property.
>
>We use the out_fence pointer received in the OUT_FENCE_PTR prop to send
>the sync_file fd back to userspace.
>
>The sync_file and fd are allocated/created before commit, but the
>fd_install operation only happens after we know that commit succeed.
>
>v2: Comment by Rob Clark:
>	- Squash commit that adds DRM_MODE_ATOMIC_OUT_FENCE flag here.
>
>    Comment by Daniel Vetter:
>	- Add clean up code for out_fences
>
>v3: Comments by Daniel Vetter:
>	- create DRM_MODE_ATOMIC_EVENT_MASK
>	- userspace should fill out_fences_ptr with the crtc_ids for which
>	it wants fences back.
>
>v4: Create OUT_FENCE_PTR properties and remove old approach.
>
>v5: Comments by Brian Starkey:
>	- Remove extra fence_get() in atomic_ioctl()
>	- Check ret before iterating on the crtc_state
>	- check ret before fd_install
>	- set fence_state to NULL at the beginning
>	- check fence_state->out_fence_ptr before put_user()
>	- change order of fput() and put_unused_fd() on failure
>
>     - Add access_ok() check to the out_fence_ptr received
>     - Rebase after fence -> dma_fence rename
>     - Store out_fence_ptr in the drm_atomic_state
>     - Split crtc_setup_out_fence()
>     - return -1 as out_fence with TEST_ONLY flag
>
>v6: Comments by Daniel Vetter
>	- Add prepare/unprepare_crtc_signaling()
>	- move struct drm_out_fence_state to drm_atomic.c
>	- mark get_crtc_fence() as static
>
>    Comments by Brian Starkey
>	- proper set fence_ptr fence_state array
>	- isolate fence_idx increment
>
>    - improve error handling
>
>v7: Comments by Daniel Vetter
>	- remove prefix from internal functions
>	- make out_fence_ptr an s64 pointer
>	- degrade DRM_INFO to DRM_DEBUG_ATOMIC when put_user fail
>	- fix doc issues
>	- filter out OUT_FENCE_PTR == NULL and do not fail in this case
>	- add complete_crtc_signalling()
>	- krealloc fence_state on demand
>
>    Comment by Brian Starkey
>	- remove unused crtc_state arg from get_out_fence()
>
>v8: Comment by Brian Starkey
>	- cancel events before check for !fence_state
>	- convert a few lefovers u64 types for out_fence_ptr
>	- fix memleak by assign fence_state earlier after realloc
>	- proper accout num_fences in case of error
>
>v9: Comment by Brian Starkey
>	- memset last position of fence_state after krealloc
>    Comments by Sean Paul
>	- pass install_fds in complete_crtc_signaling() instead of ret
>
>     - put_user(-1, fence_ptr) when decoding props
>
>Signed-off-by: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
>---
> drivers/gpu/drm/drm_atomic.c | 241 +++++++++++++++++++++++++++++++++++--------
> drivers/gpu/drm/drm_crtc.c   |   8 ++
> include/drm/drm_atomic.h     |   1 +
> include/drm/drm_crtc.h       |   6 ++
> 4 files changed, 211 insertions(+), 45 deletions(-)
>
>diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
>index 3ad780a..27e5c0a 100644
>--- a/drivers/gpu/drm/drm_atomic.c
>+++ b/drivers/gpu/drm/drm_atomic.c
>@@ -290,6 +290,23 @@ drm_atomic_get_crtc_state(struct drm_atomic_state *state,
> }
> EXPORT_SYMBOL(drm_atomic_get_crtc_state);
>
>+static void set_out_fence_for_crtc(struct drm_atomic_state *state,
>+				   struct drm_crtc *crtc, s64 __user *fence_ptr)
>+{
>+	state->crtcs[drm_crtc_index(crtc)].out_fence_ptr = fence_ptr;
>+}
>+
>+static s64 __user * get_out_fence_for_crtc(struct drm_atomic_state *state,
>+					   struct drm_crtc *crtc)
>+{
>+	s64 __user *fence_ptr;
>+
>+	fence_ptr = state->crtcs[drm_crtc_index(crtc)].out_fence_ptr;
>+	state->crtcs[drm_crtc_index(crtc)].out_fence_ptr = NULL;
>+
>+	return fence_ptr;
>+}
>+
> /**
>  * drm_atomic_set_mode_for_crtc - set mode for CRTC
>  * @state: the CRTC whose incoming state to update
>@@ -494,6 +511,16 @@ int drm_atomic_crtc_set_property(struct drm_crtc *crtc,
> 					&replaced);
> 		state->color_mgmt_changed |= replaced;
> 		return ret;
>+	} else if (property == config->prop_out_fence_ptr) {
>+		s64 __user *fence_ptr = u64_to_user_ptr(val);
>+
>+		if (!fence_ptr)
>+			return 0;
>+
>+		if (put_user(-1, fence_ptr))
>+			return -EFAULT;
>+
>+		set_out_fence_for_crtc(state->state, crtc, fence_ptr);
> 	} else if (crtc->funcs->atomic_set_property)
> 		return crtc->funcs->atomic_set_property(crtc, state, property, val);
> 	else
>@@ -536,6 +563,8 @@ drm_atomic_crtc_get_property(struct drm_crtc *crtc,
> 		*val = (state->ctm) ? state->ctm->base.id : 0;
> 	else if (property == config->gamma_lut_property)
> 		*val = (state->gamma_lut) ? state->gamma_lut->base.id : 0;
>+	else if (property == config->prop_out_fence_ptr)
>+		*val = 0;
> 	else if (crtc->funcs->atomic_get_property)
> 		return crtc->funcs->atomic_get_property(crtc, state, property, val);
> 	else
>@@ -1664,11 +1693,9 @@ int drm_atomic_debugfs_init(struct drm_minor *minor)
>  */
>
> static struct drm_pending_vblank_event *create_vblank_event(
>-		struct drm_device *dev, struct drm_file *file_priv,
>-		struct dma_fence *fence, uint64_t user_data)
>+		struct drm_device *dev, uint64_t user_data)
> {
> 	struct drm_pending_vblank_event *e = NULL;
>-	int ret;
>
> 	e = kzalloc(sizeof *e, GFP_KERNEL);
> 	if (!e)
>@@ -1678,17 +1705,6 @@ static struct drm_pending_vblank_event *create_vblank_event(
> 	e->event.base.length = sizeof(e->event);
> 	e->event.user_data = user_data;
>
>-	if (file_priv) {
>-		ret = drm_event_reserve_init(dev, file_priv, &e->base,
>-					     &e->event.base);
>-		if (ret) {
>-			kfree(e);
>-			return NULL;
>-		}
>-	}
>-
>-	e->base.fence = fence;
>-
> 	return e;
> }
>
>@@ -1793,6 +1809,165 @@ void drm_atomic_clean_old_fb(struct drm_device *dev,
> }
> EXPORT_SYMBOL(drm_atomic_clean_old_fb);
>
>+static struct dma_fence *get_crtc_fence(struct drm_crtc *crtc)
>+{
>+	struct dma_fence *fence;
>+
>+	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
>+	if (!fence)
>+		return NULL;
>+
>+	dma_fence_init(fence, &drm_crtc_fence_ops, &crtc->fence_lock,
>+		       crtc->fence_context, ++crtc->fence_seqno);
>+
>+	return fence;
>+}
>+
>+struct drm_out_fence_state {
>+	s64 __user *out_fence_ptr;
>+	struct sync_file *sync_file;
>+	int fd;
>+};
>+
>+static int setup_out_fence(struct drm_out_fence_state *fence_state,
>+			   struct dma_fence *fence)
>+{
>+	fence_state->fd = get_unused_fd_flags(O_CLOEXEC);
>+	if (fence_state->fd < 0)
>+		return fence_state->fd;
>+
>+	if (put_user(fence_state->fd, fence_state->out_fence_ptr))
>+		return -EFAULT;
>+
>+	fence_state->sync_file = sync_file_create(fence);
>+	if(!fence_state->sync_file)
>+		return -ENOMEM;
>+
>+	return 0;
>+}
>+
>+static int prepare_crtc_signaling(struct drm_device *dev,
>+				  struct drm_atomic_state *state,
>+				  struct drm_mode_atomic *arg,
>+				  struct drm_file *file_priv,
>+				  struct drm_out_fence_state **fence_state,
>+				  unsigned int *num_fences)
>+{
>+	struct drm_crtc *crtc;
>+	struct drm_crtc_state *crtc_state;
>+	int i, ret;
>+
>+	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY)
>+		return 0;
>+
>+	for_each_crtc_in_state(state, crtc, crtc_state, i) {
>+		u64 __user *fence_ptr;
>+
>+		fence_ptr = get_out_fence_for_crtc(crtc_state->state, crtc);
>+
>+		if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT || fence_ptr) {
>+			struct drm_pending_vblank_event *e;
>+
>+			e = create_vblank_event(dev, arg->user_data);
>+			if (!e)
>+				return -ENOMEM;
>+
>+			crtc_state->event = e;
>+		}
>+
>+		if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
>+			struct drm_pending_vblank_event *e = crtc_state->event;
>+
>+			if (!file_priv)
>+				continue;
>+
>+			ret = drm_event_reserve_init(dev, file_priv, &e->base,
>+						     &e->event.base);
>+			if (ret) {
>+				kfree(e);
>+				crtc_state->event = NULL;
>+				return ret;
>+			}
>+		}
>+
>+		if (fence_ptr) {
>+			struct dma_fence *fence;
>+			struct drm_out_fence_state *f;
>+
>+			f = krealloc(*fence_state, sizeof(**fence_state) *
>+				     (*num_fences + 1), GFP_KERNEL);
>+			if (!f)
>+				return -ENOMEM;
>+
>+			memset(&f[*num_fences], 0, sizeof(*f));
>+
>+			f[*num_fences].out_fence_ptr = fence_ptr;
>+			*fence_state = f;
>+
>+			fence = get_crtc_fence(crtc);
>+			if (!fence) {
>+				(*num_fences)++;
>+				return -ENOMEM;
>+			}
>+
>+			ret = setup_out_fence(&f[(*num_fences)++], fence);
>+			if (ret) {
>+				dma_fence_put(fence);
>+				return ret;
>+			}
>+
>+			crtc_state->event->base.fence = fence;
>+		}
>+	}
>+
>+	return 0;
>+}
>+
>+static void complete_crtc_signaling(struct drm_device *dev,
>+				     struct drm_atomic_state *state,
>+				     struct drm_out_fence_state *fence_state,
>+				     unsigned int num_fences,
>+				     bool install_fds)
>+{
>+	struct drm_crtc *crtc;
>+	struct drm_crtc_state *crtc_state;
>+	int i;
>+
>+	if (install_fds) {
>+		for (i = 0; i < num_fences; i++)
>+			fd_install(fence_state[i].fd,
>+				   fence_state[i].sync_file->file);
>+		return;
>+	}
>+
>+	for_each_crtc_in_state(state, crtc, crtc_state, i) {
>+		/*
>+		 * TEST_ONLY and PAGE_FLIP_EVENT are mutually
>+		 * exclusive, if they weren't, this code should be
>+		 * called on success for TEST_ONLY too.
>+		 */
>+		if (crtc_state->event)
>+			drm_event_cancel_free(dev, &crtc_state->event->base);
>+	}
>+
>+	if (!fence_state)
>+		return;
>+
>+	for (i = 0; i < num_fences; i++) {
>+		if (fence_state[i].sync_file)
>+			fput(fence_state[i].sync_file->file);
>+		if (fence_state[i].fd >= 0)
>+			put_unused_fd(fence_state[i].fd);
>+
>+		/* If this fails log error to the user */
>+		if (fence_state[i].out_fence_ptr &&
>+		    put_user(-1, fence_state[i].out_fence_ptr))
>+			DRM_DEBUG_ATOMIC("Couldn't clear out_fence_ptr\n");
>+	}
>+
>+	kfree(fence_state);
>+}
>+
> int drm_mode_atomic_ioctl(struct drm_device *dev,
> 			  void *data, struct drm_file *file_priv)
> {
>@@ -1805,11 +1980,10 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
> 	struct drm_atomic_state *state;
> 	struct drm_modeset_acquire_ctx ctx;
> 	struct drm_plane *plane;
>-	struct drm_crtc *crtc;
>-	struct drm_crtc_state *crtc_state;
>+	struct drm_out_fence_state *fence_state = NULL;
> 	unsigned plane_mask;
> 	int ret = 0;
>-	unsigned int i, j;
>+	unsigned int i, j, num_fences = 0;
>
> 	/* disallow for drivers not supporting atomic: */
> 	if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
>@@ -1924,20 +2098,10 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
> 		drm_mode_object_unreference(obj);
> 	}
>
>-	if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
>-		for_each_crtc_in_state(state, crtc, crtc_state, i) {
>-			struct drm_pending_vblank_event *e;
>-
>-			e = create_vblank_event(dev, file_priv, NULL,
>-						arg->user_data);
>-			if (!e) {
>-				ret = -ENOMEM;
>-				goto out;
>-			}
>-
>-			crtc_state->event = e;
>-		}
>-	}
>+	ret = prepare_crtc_signaling(dev, state, arg, file_priv, &fence_state,
>+				     &num_fences);
>+	if (ret)
>+		goto out;
>
> 	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
> 		/*
>@@ -1957,20 +2121,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
> out:
> 	drm_atomic_clean_old_fb(dev, plane_mask, ret);
>
>-	if (ret && arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
>-		/*
>-		 * TEST_ONLY and PAGE_FLIP_EVENT are mutually exclusive,
>-		 * if they weren't, this code should be called on success
>-		 * for TEST_ONLY too.
>-		 */
>-
>-		for_each_crtc_in_state(state, crtc, crtc_state, i) {
>-			if (!crtc_state->event)
>-				continue;
>-
>-			drm_event_cancel_free(dev, &crtc_state->event->base);
>-		}
>-	}
>+	complete_crtc_signaling(dev, state, fence_state, num_fences, !ret);
>
> 	if (ret == -EDEADLK) {
> 		drm_atomic_state_clear(state);
>diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
>index 20ddaff..cf2423d 100644
>--- a/drivers/gpu/drm/drm_crtc.c
>+++ b/drivers/gpu/drm/drm_crtc.c
>@@ -274,6 +274,8 @@ int drm_crtc_init_with_planes(struct drm_device *dev, struct drm_crtc *crtc,
> 	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
> 		drm_object_attach_property(&crtc->base, config->prop_active, 0);
> 		drm_object_attach_property(&crtc->base, config->prop_mode_id, 0);
>+		drm_object_attach_property(&crtc->base,
>+					   config->prop_out_fence_ptr, 0);
> 	}
>
> 	return 0;
>@@ -434,6 +436,12 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
> 		return -ENOMEM;
> 	dev->mode_config.prop_in_fence_fd = prop;
>
>+	prop = drm_property_create_range(dev, DRM_MODE_PROP_ATOMIC,
>+			"OUT_FENCE_PTR", 0, U64_MAX);
>+	if (!prop)
>+		return -ENOMEM;
>+	dev->mode_config.prop_out_fence_ptr = prop;
>+
> 	prop = drm_property_create_object(dev, DRM_MODE_PROP_ATOMIC,
> 			"CRTC_ID", DRM_MODE_OBJECT_CRTC);
> 	if (!prop)
>diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
>index 331bb10..c0eaec7 100644
>--- a/include/drm/drm_atomic.h
>+++ b/include/drm/drm_atomic.h
>@@ -144,6 +144,7 @@ struct __drm_crtcs_state {
> 	struct drm_crtc *ptr;
> 	struct drm_crtc_state *state;
> 	struct drm_crtc_commit *commit;
>+	s64 __user *out_fence_ptr;
> };
>
> struct __drm_connnectors_state {
>diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
>index 0870de1..44571bc 100644
>--- a/include/drm/drm_crtc.h
>+++ b/include/drm/drm_crtc.h
>@@ -1264,6 +1264,12 @@ struct drm_mode_config {
> 	 */
> 	struct drm_property *prop_in_fence_fd;
> 	/**
>+	 * @prop_out_fence_ptr: Sync File fd pointer representing the
>+	 * outgoing fences for a CRTC. Userspace should provide a pointer to a
>+	 * value of type s64, and then cast that pointer to u64.
>+	 */
>+	struct drm_property *prop_out_fence_ptr;
>+	/**
> 	 * @prop_crtc_id: Default atomic plane property to specify the
> 	 * &drm_crtc.
> 	 */
>-- 
>2.5.5
>

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