On Fri, Feb 23, 2018 at 08:17:52AM -0500, Rob Clark wrote:
> From: Brian Starkey <brian.star...@arm.com>
> 
> Add the WRITEBACK_OUT_FENCE_PTR property to writeback connectors, to
> enable userspace to get a fence which will signal once the writeback is
> complete. It is not allowed to request an out-fence without a
> framebuffer attached to the connector.
> 
> A timeline is added to drm_writeback_connector for use by the writeback
> out-fences.
> 
> In the case of a commit failure or DRM_MODE_ATOMIC_TEST_ONLY, the fence
> is set to -1.
> 
> Changes from v2:
>  - Rebase onto Gustavo Padovan's v9 explicit sync series
>  - Change out_fence_ptr type to s32 __user *
>  - Set *out_fence_ptr to -1 in drm_atomic_connector_set_property
>  - Store fence in drm_writeback_job
>  Gustavo Padovan:
>  - Move out_fence_ptr out of connector_state
>  - Signal fence from drm_writeback_signal_completion instead of
>    in driver directly
> 
> Changes from v3:
>  - Rebase onto 7e9081c5aac7 drm/fence: fix memory overwrite when setting 
> out_fence fd
>    (change out_fence_ptr to s32 __user *, for real this time.)
>  - Update documentation around WRITEBACK_OUT_FENCE_PTR
> 
> Signed-off-by: Brian Starkey <brian.star...@arm.com>
> [rebased and fixed conflicts]
> Signed-off-by: Mihail Atanassov <mihail.atanas...@arm.com>
> Signed-off-by: Liviu Dudau <liviu.du...@arm.com>
> Signed-off-by: Rob Clark <robdcl...@gmail.com>

Reviewed-by: Sean Paul <seanp...@chromium.org>

> ---
>  drivers/gpu/drm/drm_atomic.c    |  99 ++++++++++++++++++++++++++++++++----
>  drivers/gpu/drm/drm_writeback.c | 109 
> +++++++++++++++++++++++++++++++++++++++-
>  include/drm/drm_atomic.h        |   8 +++
>  include/drm/drm_connector.h     |   8 +--
>  include/drm/drm_mode_config.h   |   8 +++
>  include/drm/drm_writeback.h     |  41 ++++++++++++++-
>  6 files changed, 257 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 019f131fe8be..fc8c4da409ff 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -318,6 +318,35 @@ static s32 __user *get_out_fence_for_crtc(struct 
> drm_atomic_state *state,
>       return fence_ptr;
>  }
>  
> +static int set_out_fence_for_connector(struct drm_atomic_state *state,
> +                                     struct drm_connector *connector,
> +                                     s32 __user *fence_ptr)
> +{
> +     unsigned int index = drm_connector_index(connector);
> +
> +     if (!fence_ptr)
> +             return 0;
> +
> +     if (put_user(-1, fence_ptr))
> +             return -EFAULT;
> +
> +     state->connectors[index].out_fence_ptr = fence_ptr;
> +
> +     return 0;
> +}
> +
> +static s32 __user *get_out_fence_for_connector(struct drm_atomic_state 
> *state,
> +                                            struct drm_connector *connector)
> +{
> +     unsigned int index = drm_connector_index(connector);
> +     s32 __user *fence_ptr;
> +
> +     fence_ptr = state->connectors[index].out_fence_ptr;
> +     state->connectors[index].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
> @@ -676,6 +705,12 @@ static int drm_atomic_connector_check(struct 
> drm_connector *connector,
>               return -EINVAL;
>       }
>  
> +     if (writeback_job->out_fence && !writeback_job->fb) {
> +             DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] requesting out-fence 
> without framebuffer\n",
> +                              connector->base.id, connector->name);
> +             return -EINVAL;
> +     }
> +
>       return 0;
>  }
>  
> @@ -1277,6 +1312,11 @@ static int drm_atomic_connector_set_property(struct 
> drm_connector *connector,
>               if (fb)
>                       drm_framebuffer_unreference(fb);
>               return ret;
> +     } else if (property == config->writeback_out_fence_ptr_property) {
> +             s32 __user *fence_ptr = u64_to_user_ptr(val);
> +
> +             return set_out_fence_for_connector(state->state, connector,
> +                                                fence_ptr);
>       } else if (connector->funcs->atomic_set_property) {
>               return connector->funcs->atomic_set_property(connector,
>                               state, property, val);
> @@ -1361,6 +1401,8 @@ 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->writeback_out_fence_ptr_property) {
> +             *val = 0;
>       } else if (connector->funcs->atomic_get_property) {
>               return connector->funcs->atomic_get_property(connector,
>                               state, property, val);
> @@ -2221,7 +2263,7 @@ static int setup_out_fence(struct drm_out_fence_state 
> *fence_state,
>       return 0;
>  }
>  
> -static int prepare_crtc_signaling(struct drm_device *dev,
> +static int prepare_signaling(struct drm_device *dev,
>                                 struct drm_atomic_state *state,
>                                 struct drm_mode_atomic *arg,
>                                 struct drm_file *file_priv,
> @@ -2230,6 +2272,8 @@ static int prepare_crtc_signaling(struct drm_device 
> *dev,
>  {
>       struct drm_crtc *crtc;
>       struct drm_crtc_state *crtc_state;
> +     struct drm_connector *conn;
> +     struct drm_connector_state *conn_state;
>       int i, c = 0, ret;
>  
>       if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY)
> @@ -2295,6 +2339,43 @@ static int prepare_crtc_signaling(struct drm_device 
> *dev,
>               c++;
>       }
>  
> +     for_each_new_connector_in_state(state, conn, conn_state, i) {
> +             struct drm_writeback_job *job;
> +             struct drm_out_fence_state *f;
> +             struct dma_fence *fence;
> +             s32 __user *fence_ptr;
> +
> +             fence_ptr = get_out_fence_for_connector(state, conn);
> +             if (!fence_ptr)
> +                     continue;
> +
> +             job = drm_atomic_get_writeback_job(conn_state);
> +             if (!job)
> +                     return -ENOMEM;
> +
> +             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 = drm_writeback_get_out_fence((struct 
> drm_writeback_connector *)conn);
> +             if (!fence)
> +                     return -ENOMEM;
> +
> +             ret = setup_out_fence(&f[(*num_fences)++], fence);
> +             if (ret) {
> +                     dma_fence_put(fence);
> +                     return ret;
> +             }
> +
> +             job->out_fence = fence;
> +     }
> +
>       /*
>        * Having this flag means user mode pends on event which will never
>        * reach due to lack of at least one CRTC for signaling
> @@ -2305,11 +2386,11 @@ static int prepare_crtc_signaling(struct drm_device 
> *dev,
>       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)
> +static void complete_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;
> @@ -2488,8 +2569,8 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>               drm_mode_object_put(obj);
>       }
>  
> -     ret = prepare_crtc_signaling(dev, state, arg, file_priv, &fence_state,
> -                                  &num_fences);
> +     ret = prepare_signaling(dev, state, arg, file_priv, &fence_state,
> +                             &num_fences);
>       if (ret)
>               goto out;
>  
> @@ -2507,7 +2588,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  out:
>       drm_atomic_clean_old_fb(dev, plane_mask, ret);
>  
> -     complete_crtc_signaling(dev, state, fence_state, num_fences, !ret);
> +     complete_signaling(dev, state, fence_state, num_fences, !ret);
>  
>       if (ret == -EDEADLK) {
>               drm_atomic_state_clear(state);
> diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
> index da61f929cbc3..839e79932c19 100644
> --- a/drivers/gpu/drm/drm_writeback.c
> +++ b/drivers/gpu/drm/drm_writeback.c
> @@ -13,6 +13,7 @@
>  #include <drm/drm_property.h>
>  #include <drm/drm_writeback.h>
>  #include <drm/drmP.h>
> +#include <linux/dma-fence.h>
>  
>  /**
>   * DOC: overview
> @@ -30,6 +31,16 @@
>   * framebuffer applies only to a single commit (see below). A framebuffer may
>   * not be attached while the CRTC is off.
>   *
> + * 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
> + * WRITEBACK_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 some additional properties, which userspace
>   * can use to query and control them:
>   *
> @@ -46,8 +57,54 @@
>   *   data is an array of u32 DRM_FORMAT_* fourcc values.
>   *   Userspace can use this blob to find out what pixel formats are supported
>   *   by the connector's writeback engine.
> + *
> + *  "WRITEBACK_OUT_FENCE_PTR":
> + *   Userspace can use this property to provide a pointer for the kernel to
> + *   fill with a sync_file file descriptor, which will signal once the
> + *   writeback is finished. The value should be the address of a 32-bit
> + *   signed integer, cast to a u64.
> + *   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_wb_connector(x) container_of(x->lock, \
> +                                           struct drm_writeback_connector, \
> +                                           fence_lock)
> +
> +static const char *drm_writeback_fence_get_driver_name(struct dma_fence 
> *fence)
> +{
> +     struct drm_writeback_connector *wb_connector =
> +             fence_to_wb_connector(fence);
> +
> +     return wb_connector->base.dev->driver->name;
> +}
> +
> +static const char *
> +drm_writeback_fence_get_timeline_name(struct dma_fence *fence)
> +{
> +     struct drm_writeback_connector *wb_connector =
> +             fence_to_wb_connector(fence);
> +
> +     return wb_connector->timeline_name;
> +}
> +
> +static bool drm_writeback_fence_enable_signaling(struct dma_fence *fence)
> +{
> +     return true;
> +}
> +
> +static const struct dma_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 = dma_fence_default_wait,
> +};
> +
>  static bool create_writeback_properties(struct drm_device *dev)
>  {
>       struct drm_property *prop;
> @@ -69,6 +126,15 @@ static bool create_writeback_properties(struct drm_device 
> *dev)
>               dev->mode_config.writeback_pixel_formats_property = prop;
>       }
>  
> +     if (!dev->mode_config.writeback_out_fence_ptr_property) {
> +             prop = drm_property_create_range(dev, DRM_MODE_PROP_ATOMIC,
> +                                              "WRITEBACK_OUT_FENCE_PTR", 0,
> +                                              U64_MAX);
> +             if (!prop)
> +                     return -ENOMEM;
> +             dev->mode_config.writeback_out_fence_ptr_property = prop;
> +     }
> +
>       return true;
>  }
>  
> @@ -138,6 +204,15 @@ int drm_writeback_connector_init(struct drm_device *dev,
>       INIT_LIST_HEAD(&wb_connector->job_queue);
>       spin_lock_init(&wb_connector->job_lock);
>  
> +     wb_connector->fence_context = dma_fence_context_alloc(1);
> +     spin_lock_init(&wb_connector->fence_lock);
> +     snprintf(wb_connector->timeline_name,
> +              sizeof(wb_connector->timeline_name),
> +              "CONNECTOR:%d-%s", connector->base.id, connector->name);
> +
> +     drm_object_attach_property(&connector->base,
> +                                config->writeback_out_fence_ptr_property, 0);
> +
>       drm_object_attach_property(&connector->base,
>                                  config->writeback_fb_id_property, 0);
>  
> @@ -200,6 +275,7 @@ void drm_writeback_cleanup_job(struct drm_writeback_job 
> *job)
>  
>       if (job->fb)
>               drm_framebuffer_unreference(job->fb);
> +     dma_fence_put(job->out_fence);
>       kfree(job);
>  }
>  EXPORT_SYMBOL(drm_writeback_cleanup_job);
> @@ -222,6 +298,7 @@ static void cleanup_work(struct work_struct *work)
>  /**
>   * drm_writeback_signal_completion - Signal the completion of a writeback job
>   * @wb_connector: The writeback connector whose job is complete
> + * @status: Status code to set in the writeback out_fence (0 for success)
>   *
>   * Drivers should call this to signal the completion of a previously queued
>   * writeback job. It should be called as soon as possible after the hardware
> @@ -235,7 +312,8 @@ static void cleanup_work(struct work_struct *work)
>   * See also: drm_writeback_queue_job()
>   */
>  void
> -drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector)
> +drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
> +                             int status)
>  {
>       unsigned long flags;
>       struct drm_writeback_job *job;
> @@ -244,8 +322,14 @@ drm_writeback_signal_completion(struct 
> drm_writeback_connector *wb_connector)
>       job = list_first_entry_or_null(&wb_connector->job_queue,
>                                      struct drm_writeback_job,
>                                      list_entry);
> -     if (job)
> +     if (job) {
>               list_del(&job->list_entry);
> +             if (job->out_fence) {
> +                     if (status)
> +                             dma_fence_set_error(job->out_fence, status);
> +                     dma_fence_signal(job->out_fence);
> +             }
> +     }
>       spin_unlock_irqrestore(&wb_connector->job_lock, flags);
>  
>       if (WARN_ON(!job))
> @@ -255,3 +339,24 @@ drm_writeback_signal_completion(struct 
> drm_writeback_connector *wb_connector)
>       queue_work(system_long_wq, &job->cleanup_work);
>  }
>  EXPORT_SYMBOL(drm_writeback_signal_completion);
> +
> +struct dma_fence *
> +drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector)
> +{
> +     struct dma_fence *fence;
> +
> +     if (WARN_ON(wb_connector->base.connector_type !=
> +                 DRM_MODE_CONNECTOR_WRITEBACK))
> +             return NULL;
> +
> +     fence = kzalloc(sizeof(*fence), GFP_KERNEL);
> +     if (!fence)
> +             return NULL;
> +
> +     dma_fence_init(fence, &drm_writeback_fence_ops,
> +                    &wb_connector->fence_lock, wb_connector->fence_context,
> +                    ++wb_connector->fence_seqno);
> +
> +     return fence;
> +}
> +EXPORT_SYMBOL(drm_writeback_get_out_fence);
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index d7b0263cc5cf..09076a625637 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -160,6 +160,14 @@ struct __drm_crtcs_state {
>  struct __drm_connnectors_state {
>       struct drm_connector *ptr;
>       struct drm_connector_state *state, *old_state, *new_state;
> +     /**
> +      * @out_fence_ptr:
> +      *
> +      * User-provided pointer which the kernel uses to return a sync_file
> +      * file descriptor. Used by writeback connectors to signal completion of
> +      * the writeback.
> +      */
> +     s32 __user *out_fence_ptr;
>  };
>  
>  struct drm_private_obj;
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 8701ebcc68b3..da56fda6e218 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -429,10 +429,10 @@ struct drm_connector_state {
>       /**
>        * @writeback_job: Writeback job for writeback connectors
>        *
> -      * Holds the framebuffer for a writeback connector. As the writeback
> -      * completion may be asynchronous to the normal commit cycle, the
> -      * writeback job lifetime is managed separately from the normal atomic
> -      * state by this object.
> +      * Holds the framebuffer and out-fence for a writeback connector. As
> +      * the writeback completion may be asynchronous to the normal commit
> +      * cycle, the writeback job lifetime is managed separately from the
> +      * normal atomic state by this object.
>        *
>        * See also: drm_writeback_queue_job() and
>        * drm_writeback_signal_completion()
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index c012e1148ec0..930e00560380 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -792,6 +792,14 @@ struct drm_mode_config {
>        * See also: drm_writeback_connector_init()
>        */
>       struct drm_property *writeback_pixel_formats_property;
> +     /**
> +      * @writeback_out_fence_ptr_property: Property for writeback connectors,
> +      * fd pointer representing the outgoing fences for a writeback
> +      * connector. Userspace should provide a pointer to a value of type s32,
> +      * and then cast that pointer to u64.
> +      * See also: drm_writeback_connector_init()
> +      */
> +     struct drm_property *writeback_out_fence_ptr_property;
>  
>       /* dumb ioctl parameters */
>       uint32_t preferred_depth, prefer_shadow;
> diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
> index 0bb95fd4907d..b9470ae2a53d 100644
> --- a/include/drm/drm_writeback.h
> +++ b/include/drm/drm_writeback.h
> @@ -49,6 +49,32 @@ struct drm_writeback_connector {
>        * drm_writeback_signal_completion()
>        */
>       struct list_head job_queue;
> +
> +     /**
> +      * @fence_context:
> +      *
> +      * timeline context used for fence operations.
> +      */
> +     unsigned int fence_context;
> +     /**
> +      * @fence_lock:
> +      *
> +      * spinlock to protect the fences in the fence_context.
> +      */
> +     spinlock_t fence_lock;
> +     /**
> +      * @fence_seqno:
> +      *
> +      * Seqno variable used as monotonic counter for the fences
> +      * created on the connector's timeline.
> +      */
> +     unsigned long fence_seqno;
> +     /**
> +      * @timeline_name:
> +      *
> +      * The name of the connector's fence timeline.
> +      */
> +     char timeline_name[32];
>  };
>  #define to_wb_connector(x) container_of(x, struct drm_writeback_connector, 
> base)
>  
> @@ -73,6 +99,13 @@ struct drm_writeback_job {
>        * directly, use drm_atomic_set_writeback_fb_for_connector()
>        */
>       struct drm_framebuffer *fb;
> +
> +     /**
> +      * @out_fence:
> +      *
> +      * Fence which will signal once the writeback has completed
> +      */
> +     struct dma_fence *out_fence;
>  };
>  
>  int drm_writeback_connector_init(struct drm_device *dev,
> @@ -85,5 +118,11 @@ void drm_writeback_queue_job(struct 
> drm_writeback_connector *wb_connector,
>                            struct drm_writeback_job *job);
>  
>  void drm_writeback_cleanup_job(struct drm_writeback_job *job);
> -void drm_writeback_signal_completion(struct drm_writeback_connector 
> *wb_connector);
> +
> +void
> +drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
> +                             int status);
> +
> +struct dma_fence *
> +drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector);
>  #endif
> -- 
> 2.14.3
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS
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