Message-ID: <20161026124624.GC30071@e106950-lin.cambridge.arm.com>
Date:   Wed, 26 Oct 2016 13:46:24 +0100
From:   Brian Starkey <brian.starkey@....com>
To:     dri-devel@...ts.freedesktop.org
Cc:     gustavo@...ovan.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org
Subject: Re: [RFC PATCH v2 8/9] drm: writeback: Add out-fences for writeback
 connectors

Hi Gustavo,

It would be great if you could cast your eye over this one as-well.
My intention was to be as similar to the CRTC out-fences as possible.

Thanks,
Brian

On Wed, Oct 26, 2016 at 09:55:07AM +0100, Brian Starkey wrote:
>Add the OUT_FENCE_PTR property to writeback connectors, to enable
>userspace to get a fence which will signal once the writeback is
>complete.
>
>A timeline is added to drm_connector for use by the writeback
>out-fences. It is up to drivers to check for a fence in the
>connector_state and signal the it appropriately when their writeback has
>finished.
>
>It is not allowed to request an out-fence without a framebuffer attached
>to the connector.
>
>Signed-off-by: Brian Starkey <brian.starkey@....com>
>---
> drivers/gpu/drm/drm_atomic.c        |   60 +++++++++++++++++++++++---
> drivers/gpu/drm/drm_atomic_helper.c |    5 ++-
> drivers/gpu/drm/drm_writeback.c     |   80 +++++++++++++++++++++++++++++++++++
> include/drm/drm_connector.h         |   14 ++++++
> include/drm/drm_writeback.h         |    2 +
> 5 files changed, 155 insertions(+), 6 deletions(-)
>
>diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
>index 3f8fc97..061ea13 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 <drm/drm_writeback.h>
> #include <linux/sync_file.h>
>
> #include "drm_crtc_internal.h"
>@@ -646,6 +647,12 @@ static int drm_atomic_connector_check(struct drm_connector *connector,
> 		return -EINVAL;
> 	}
>
>+	if (state->out_fence && !state->fb) {
>+		DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] requesting out-fence without framebuffer\n",
>+				 connector->base.id, connector->name);
>+		return -EINVAL;
>+	}
>+
> 	return 0;
> }
>
>@@ -1047,6 +1054,8 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
> 		drm_atomic_set_fb_for_connector(state, fb);
> 		if (fb)
> 			drm_framebuffer_unreference(fb);
>+	} else if (property == config->prop_out_fence_ptr) {
>+		state->out_fence_ptr = u64_to_user_ptr(val);
> 	} else if (connector->funcs->atomic_set_property) {
> 		return connector->funcs->atomic_set_property(connector,
> 				state, property, val);
>@@ -1088,6 +1097,8 @@ drm_atomic_connector_get_property(struct drm_connector *connector,
> 	} else if (property == config->writeback_fb_id_property) {
> 		/* Writeback framebuffer is one-shot, write and forget */
> 		*val = 0;
>+	} else if (property == config->prop_out_fence_ptr) {
>+		*val = 0;
> 	} else if (connector->funcs->atomic_get_property) {
> 		return connector->funcs->atomic_get_property(connector,
> 				state, property, val);
>@@ -1736,6 +1747,39 @@ static int setup_out_fence(struct drm_out_fence_state *fence_state,
> 	return 0;
> }
>
>+static int setup_connector_out_fences(struct drm_atomic_state *state,
>+				      struct drm_out_fence_state *fence_state,
>+				      int *fence_idx)
>+{
>+	struct drm_connector *conn;
>+	struct drm_connector_state *conn_state;
>+	int i, ret;
>+
>+	for_each_connector_in_state(state, conn, conn_state, i) {
>+		struct fence *fence;
>+
>+		if (!conn_state->out_fence_ptr)
>+			continue;
>+
>+		fence = drm_writeback_get_out_fence(conn, conn_state);
>+		if (!fence)
>+			return -ENOMEM;
>+
>+		ret = setup_out_fence(&fence_state[(*fence_idx)++],
>+				      conn_state->out_fence_ptr,
>+				      fence);
>+		if (ret) {
>+			fence_put(fence);
>+			return ret;
>+		}
>+
>+		/* One-time usage only */
>+		conn_state->out_fence_ptr = NULL;
>+	}
>+
>+	return 0;
>+}
>+
> int drm_mode_atomic_ioctl(struct drm_device *dev,
> 			  void *data, struct drm_file *file_priv)
> {
>@@ -1868,8 +1912,8 @@ retry:
> 		drm_mode_object_unreference(obj);
> 	}
>
>-	fence_state = kcalloc(dev->mode_config.num_crtc, sizeof(*fence_state),
>-			      GFP_KERNEL);
>+	fence_state = kcalloc(dev->mode_config.num_crtc + state->num_connector,
>+			      sizeof(*fence_state), GFP_KERNEL);
> 	if (!fence_state) {
> 		ret = -ENOMEM;
> 		goto out;
>@@ -1929,10 +1973,16 @@ retry:
> 		 * Below we call drm_atomic_state_free for it.
> 		 */
> 		ret = drm_atomic_check_only(state);
>-	} else if (arg->flags & DRM_MODE_ATOMIC_NONBLOCK) {
>-		ret = drm_atomic_nonblocking_commit(state);
> 	} else {
>-		ret = drm_atomic_commit(state);
>+		ret = setup_connector_out_fences(state, fence_state,
>+						 &fence_idx);
>+		if (ret)
>+			goto out;
>+
>+		if (arg->flags & DRM_MODE_ATOMIC_NONBLOCK)
>+			ret = drm_atomic_nonblocking_commit(state);
>+		else
>+			ret = drm_atomic_commit(state);
> 	}
>
> 	if (!ret)
>diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
>index bba8672..88da299 100644
>--- a/drivers/gpu/drm/drm_atomic_helper.c
>+++ b/drivers/gpu/drm/drm_atomic_helper.c
>@@ -3234,8 +3234,9 @@ __drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector,
> 	if (state->crtc)
> 		drm_connector_reference(connector);
>
>-	/* Don't copy over framebuffers, they are used only once */
>+	/* Don't copy over framebuffers or fences, they are used only once */
> 	state->fb = NULL;
>+	state->out_fence = NULL;
> }
> EXPORT_SYMBOL(__drm_atomic_helper_connector_duplicate_state);
>
>@@ -3365,6 +3366,8 @@ __drm_atomic_helper_connector_destroy_state(struct drm_connector_state *state)
> 		drm_connector_unreference(state->connector);
> 	if (state->fb)
> 		drm_framebuffer_unreference(state->fb);
>+
>+	fence_put(state->out_fence);
> }
> EXPORT_SYMBOL(__drm_atomic_helper_connector_destroy_state);
>
>diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
>index 5a6e0ad..4a6ef30 100644
>--- a/drivers/gpu/drm/drm_writeback.c
>+++ b/drivers/gpu/drm/drm_writeback.c
>@@ -11,6 +11,7 @@
> #include <drm/drm_crtc.h>
> #include <drm/drm_property.h>
> #include <drm/drmP.h>
>+#include <linux/fence.h>
>
> /**
>  * DOC: overview
>@@ -32,6 +33,16 @@
>  * explicitly cleared in order to make a subsequent commit which doesn't use
>  * writeback.
>  *
>+ * Unlike with planes, when a writeback framebuffer is removed by userspace DRM
>+ * makes no attempt to remove it from active use by the connector. This is
>+ * because no method is provided to abort a writeback operation, and in any
>+ * case making a new commit whilst a writeback is ongoing is undefined (see
>+ * OUT_FENCE_PTR below). As soon as the current writeback is finished, the
>+ * framebuffer will automatically no longer be in active use. As it will also
>+ * have already been removed from the framebuffer list, there will be no way for
>+ * any userspace application to retrieve a reference to it in the intervening
>+ * period.
>+ *
>  * Writeback connectors have several additional properties, which userspace
>  * can use to query and control them:
>  *
>@@ -52,8 +63,48 @@
>  *  "PIXEL_FORMATS_SIZE":
>  *	Immutable unsigned range property storing the number of entries in the
>  *	PIXEL_FORMATS array.
>+ *
>+ *  "OUT_FENCE_PTR":
>+ *	Userspace can provide the address of a 64-bit integer in this property,
>+ *	which will be filled with a sync_file file descriptor by the kernel.
>+ *	The sync_file will signal when the associated writeback has finished.
>+ *	Userspace should wait for this fence to signal before making another
>+ *	commit affecting any of the same CRTCs, Planes or Connectors.
>+ *	**Failure to do so will result in undefined behaviour.**
>+ *	For this reason it is strongly recommended that all userspace
>+ *	applications making use of writeback connectors *always* retrieve an
>+ *	out-fence for the commit and use it appropriately.
>+ *	From userspace, this property will always read as zero.
>  */
>
>+#define fence_to_connector(x) container_of(x->lock, struct drm_connector, fence_lock)
>+
>+static const char *drm_writeback_fence_get_driver_name(struct fence *fence)
>+{
>+	struct drm_connector *connector = fence_to_connector(fence);
>+
>+	return connector->dev->driver->name;
>+}
>+
>+static const char *drm_writeback_fence_get_timeline_name(struct fence *fence)
>+{
>+	struct drm_connector *connector = fence_to_connector(fence);
>+
>+	return connector->timeline_name;
>+}
>+
>+static bool drm_writeback_fence_enable_signaling(struct fence *fence)
>+{
>+	return true;
>+}
>+
>+static const struct fence_ops drm_writeback_fence_ops = {
>+	.get_driver_name = drm_writeback_fence_get_driver_name,
>+	.get_timeline_name = drm_writeback_fence_get_timeline_name,
>+	.enable_signaling = drm_writeback_fence_enable_signaling,
>+	.wait = fence_default_wait,
>+};
>+
> /**
>  * create_writeback_properties - Create writeback connector-specific properties
>  * @dev: DRM device
>@@ -136,6 +187,14 @@ int drm_writeback_connector_init(struct drm_device *dev,
> 	if (ret)
> 		goto fail;
>
>+	connector->fence_context = fence_context_alloc(1);
>+	spin_lock_init(&connector->fence_lock);
>+	snprintf(connector->timeline_name, sizeof(connector->timeline_name),
>+		 "CONNECTOR:%d", connector->base.id);
>+
>+	drm_object_attach_property(&connector->base,
>+				   config->prop_out_fence_ptr, 0);
>+
> 	drm_object_attach_property(&connector->base,
> 				   config->writeback_fb_id_property, 0);
>
>@@ -155,3 +214,24 @@ fail:
> 	return ret;
> }
> EXPORT_SYMBOL(drm_writeback_connector_init);
>+
>+struct fence *drm_writeback_get_out_fence(struct drm_connector *connector,
>+					  struct drm_connector_state *conn_state)
>+{
>+	struct fence *fence;
>+
>+	if (WARN_ON(connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK))
>+		return NULL;
>+
>+	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
>+	if (!fence)
>+		return NULL;
>+
>+	fence_init(fence, &drm_writeback_fence_ops, &connector->fence_lock,
>+		   connector->fence_context, ++connector->fence_seqno);
>+
>+	conn_state->out_fence = fence_get(fence);
>+
>+	return fence;
>+}
>+EXPORT_SYMBOL(drm_writeback_get_out_fence);
>diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
>index a5e3778..7d40537 100644
>--- a/include/drm/drm_connector.h
>+++ b/include/drm/drm_connector.h
>@@ -199,6 +199,7 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
>  * @best_encoder: can be used by helpers and drivers to select the encoder
>  * @state: backpointer to global drm_atomic_state
>  * @fb: Writeback framebuffer, for DRM_MODE_CONNECTOR_WRITEBACK
>+ * @out_fence: Fence which will clear when the framebuffer write has finished
>  */
> struct drm_connector_state {
> 	struct drm_connector *connector;
>@@ -216,6 +217,9 @@ struct drm_connector_state {
> 	struct drm_atomic_state *state;
>
> 	struct drm_framebuffer *fb;  /* do not write directly, use drm_atomic_set_fb_for_connector() */
>+
>+	struct fence *out_fence;
>+	u64 __user *out_fence_ptr;
> };
>
> /**
>@@ -546,6 +550,10 @@ struct drm_cmdline_mode {
>  * @tile_v_loc: vertical location of this tile
>  * @tile_h_size: horizontal size of this tile.
>  * @tile_v_size: vertical size of this tile.
>+ * @fence_context: context for fence signalling
>+ * @fence_lock: fence lock for the fence context
>+ * @fence_seqno: seqno variable to create fences
>+ * @timeline_name: fence timeline name
>  *
>  * Each connector may be connected to one or more CRTCs, or may be clonable by
>  * another connector if they can share a CRTC.  Each connector also has a specific
>@@ -694,6 +702,12 @@ struct drm_connector {
> 	uint8_t num_h_tile, num_v_tile;
> 	uint8_t tile_h_loc, tile_v_loc;
> 	uint16_t tile_h_size, tile_v_size;
>+
>+	/* fence timelines info for DRM out-fences */
>+	unsigned int fence_context;
>+	spinlock_t fence_lock;
>+	unsigned long fence_seqno;
>+	char timeline_name[32];
> };
>
> #define obj_to_connector(x) container_of(x, struct drm_connector, base)
>diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
>index afdc2742..01f33bc 100644
>--- a/include/drm/drm_writeback.h
>+++ b/include/drm/drm_writeback.h
>@@ -16,4 +16,6 @@ int drm_writeback_connector_init(struct drm_device *dev,
> 				 const struct drm_connector_funcs *funcs,
> 				 u32 *formats, int n_formats);
>
>+struct fence *drm_writeback_get_out_fence(struct drm_connector *connector,
>+					  struct drm_connector_state *conn_state);
> #endif
>-- 
>1.7.9.5
>

Powered by blists - more mailing lists