Re: [PATCH v4 09/14] drm/syncobj: Add deadline support for syncobj waits

[Pekka Paalanen <ppaalanen@gmail.com>]

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On Sat, 18 Feb 2023 13:15:52 -0800
Rob Clark <robdclark@gmail.com> wrote:

> From: Rob Clark <robdclark@chromium.org>
> 
> Add a new flag to let userspace provide a deadline as a hint for syncobj
> and timeline waits.  This gives a hint to the driver signaling the
> backing fences about how soon userspace needs it to compete work, so it
> can addjust GPU frequency accordingly.  An immediate deadline can be
> given to provide something equivalent to i915 "wait boost".
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
> 
> I'm a bit on the fence about the addition of the DRM_CAP, but it seems
> useful to give userspace a way to probe whether the kernel and driver
> supports the new wait flag, especially since we have vk-common code
> dealing with syncobjs.  But open to suggestions.
> 
>  drivers/gpu/drm/drm_ioctl.c   |  3 ++
>  drivers/gpu/drm/drm_syncobj.c | 59 ++++++++++++++++++++++++++++-------
>  include/drm/drm_drv.h         |  6 ++++
>  include/uapi/drm/drm.h        | 16 ++++++++--
>  4 files changed, 71 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> index 7c9d66ee917d..1c5c942cf0f9 100644
> --- a/drivers/gpu/drm/drm_ioctl.c
> +++ b/drivers/gpu/drm/drm_ioctl.c
> @@ -254,6 +254,9 @@ static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_
>  	case DRM_CAP_SYNCOBJ_TIMELINE:
>  		req->value = drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE);
>  		return 0;
> +	case DRM_CAP_SYNCOBJ_DEADLINE:
> +		req->value = drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE);

Hi,

is that a typo for DRIVER_SYNCOBJ_DEADLINE?

> +		return 0;
>  	}
>  
>  	/* Other caps only work with KMS drivers */
> diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
> index 0c2be8360525..61cf97972a60 100644
> --- a/drivers/gpu/drm/drm_syncobj.c
> +++ b/drivers/gpu/drm/drm_syncobj.c
> @@ -973,7 +973,8 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
>  						  uint32_t count,
>  						  uint32_t flags,
>  						  signed long timeout,
> -						  uint32_t *idx)
> +						  uint32_t *idx,
> +						  ktime_t *deadline)
>  {
>  	struct syncobj_wait_entry *entries;
>  	struct dma_fence *fence;
> @@ -1053,6 +1054,15 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
>  			drm_syncobj_fence_add_wait(syncobjs[i], &entries[i]);
>  	}
>  
> +	if (deadline) {
> +		for (i = 0; i < count; ++i) {
> +			fence = entries[i].fence;
> +			if (!fence)
> +				continue;
> +			dma_fence_set_deadline(fence, *deadline);
> +		}
> +	}
> +
>  	do {
>  		set_current_state(TASK_INTERRUPTIBLE);
>  
> @@ -1151,7 +1161,8 @@ static int drm_syncobj_array_wait(struct drm_device *dev,
>  				  struct drm_file *file_private,
>  				  struct drm_syncobj_wait *wait,
>  				  struct drm_syncobj_timeline_wait *timeline_wait,
> -				  struct drm_syncobj **syncobjs, bool timeline)
> +				  struct drm_syncobj **syncobjs, bool timeline,
> +				  ktime_t *deadline)
>  {
>  	signed long timeout = 0;
>  	uint32_t first = ~0;
> @@ -1162,7 +1173,8 @@ static int drm_syncobj_array_wait(struct drm_device *dev,
>  							 NULL,
>  							 wait->count_handles,
>  							 wait->flags,
> -							 timeout, &first);
> +							 timeout, &first,
> +							 deadline);
>  		if (timeout < 0)
>  			return timeout;
>  		wait->first_signaled = first;
> @@ -1172,7 +1184,8 @@ static int drm_syncobj_array_wait(struct drm_device *dev,
>  							 u64_to_user_ptr(timeline_wait->points),
>  							 timeline_wait->count_handles,
>  							 timeline_wait->flags,
> -							 timeout, &first);
> +							 timeout, &first,
> +							 deadline);
>  		if (timeout < 0)
>  			return timeout;
>  		timeline_wait->first_signaled = first;
> @@ -1243,13 +1256,20 @@ drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
>  {
>  	struct drm_syncobj_wait *args = data;
>  	struct drm_syncobj **syncobjs;
> +	unsigned possible_flags;
> +	ktime_t t, *tp = NULL;
>  	int ret = 0;
>  
>  	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
>  		return -EOPNOTSUPP;
>  
> -	if (args->flags & ~(DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL |
> -			    DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT))
> +	possible_flags = DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL |
> +			 DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT;
> +
> +	if (drm_core_check_feature(dev, DRIVER_SYNCOBJ_DEADLINE))
> +		possible_flags |= DRM_SYNCOBJ_WAIT_FLAGS_WAIT_DEADLINE;
> +
> +	if (args->flags & ~possible_flags)
>  		return -EINVAL;
>  
>  	if (args->count_handles == 0)
> @@ -1262,8 +1282,13 @@ drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
>  	if (ret < 0)
>  		return ret;
>  
> +	if (args->flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_DEADLINE) {
> +		t = ktime_set(args->deadline_sec, args->deadline_nsec);
> +		tp = &t;
> +	}
> +
>  	ret = drm_syncobj_array_wait(dev, file_private,
> -				     args, NULL, syncobjs, false);
> +				     args, NULL, syncobjs, false, tp);
>  
>  	drm_syncobj_array_free(syncobjs, args->count_handles);
>  
> @@ -1276,14 +1301,21 @@ drm_syncobj_timeline_wait_ioctl(struct drm_device *dev, void *data,
>  {
>  	struct drm_syncobj_timeline_wait *args = data;
>  	struct drm_syncobj **syncobjs;
> +	unsigned possible_flags;
> +	ktime_t t, *tp = NULL;
>  	int ret = 0;
>  
>  	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
>  		return -EOPNOTSUPP;
>  
> -	if (args->flags & ~(DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL |
> -			    DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT |
> -			    DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE))
> +	possible_flags = DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL |
> +			 DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT |
> +			 DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE;
> +
> +	if (drm_core_check_feature(dev, DRIVER_SYNCOBJ_DEADLINE))
> +		possible_flags |= DRM_SYNCOBJ_WAIT_FLAGS_WAIT_DEADLINE;
> +
> +	if (args->flags & ~possible_flags)
>  		return -EINVAL;
>  
>  	if (args->count_handles == 0)
> @@ -1296,8 +1328,13 @@ drm_syncobj_timeline_wait_ioctl(struct drm_device *dev, void *data,
>  	if (ret < 0)
>  		return ret;
>  
> +	if (args->flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_DEADLINE) {
> +		t = ktime_set(args->deadline_sec, args->deadline_nsec);
> +		tp = &t;
> +	}
> +
>  	ret = drm_syncobj_array_wait(dev, file_private,
> -				     NULL, args, syncobjs, true);
> +				     NULL, args, syncobjs, true, tp);
>  
>  	drm_syncobj_array_free(syncobjs, args->count_handles);
>  
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 1d76d0686b03..9aa24f097e22 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -104,6 +104,12 @@ enum drm_driver_feature {
>  	 * acceleration should be handled by two drivers that are connected using auxiliary bus.
>  	 */
>  	DRIVER_COMPUTE_ACCEL            = BIT(7),
> +	/**
> +	 * @DRIVER_SYNCOBJ_DEADLINE:
> +	 *
> +	 * Driver supports &dma_fence_ops.set_deadline
> +	 */
> +	DRIVER_SYNCOBJ_DEADLINE         = BIT(8),
>  
>  	/* IMPORTANT: Below are all the legacy flags, add new ones above. */
>  
> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> index 642808520d92..c6b85bb13810 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -767,6 +767,13 @@ struct drm_gem_open {
>   * Documentation/gpu/drm-mm.rst, section "DRM Sync Objects".
>   */
>  #define DRM_CAP_SYNCOBJ_TIMELINE	0x14
> +/**
> + * DRM_CAP_SYNCOBJ_DEADLINE
> + *
> + * If set to 1, the driver supports DRM_SYNCOBJ_WAIT_FLAGS_WAIT_DEADLINE flag
> + * on the SYNCOBJ_TIMELINE_WAIT/SYNCOBJ_WAIT ioctls.
> + */
> +#define DRM_CAP_SYNCOBJ_DEADLINE	0x15
>  
>  /* DRM_IOCTL_GET_CAP ioctl argument type */
>  struct drm_get_cap {
> @@ -887,6 +894,7 @@ struct drm_syncobj_transfer {
>  #define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL (1 << 0)
>  #define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT (1 << 1)
>  #define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE (1 << 2) /* wait for time point to become available */
> +#define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_DEADLINE (1 << 3) /* set fence deadline based to deadline_nsec/sec */

Where was the UAPI documentation explaining what a fence deadline is
and what it does, again?

>  struct drm_syncobj_wait {
>  	__u64 handles;
>  	/* absolute timeout */
> @@ -894,7 +902,9 @@ struct drm_syncobj_wait {
>  	__u32 count_handles;
>  	__u32 flags;
>  	__u32 first_signaled; /* only valid when not waiting all */
> -	__u32 pad;
> +	/* Deadline to set on backing fence(s) in CLOCK_MONOTONIC: */
> +	__u32 deadline_nsec;
> +	__u64 deadline_sec;
>  };
>  
>  struct drm_syncobj_timeline_wait {
> @@ -906,7 +916,9 @@ struct drm_syncobj_timeline_wait {
>  	__u32 count_handles;
>  	__u32 flags;
>  	__u32 first_signaled; /* only valid when not waiting all */
> -	__u32 pad;
> +	/* Deadline to set on backing fence(s) in CLOCK_MONOTONIC: */
> +	__u32 deadline_nsec;
> +	__u64 deadline_sec;
>  };

It seems inconsistent that these sec,nsec are here unsigned, when in
other places they are signed. There is also the question if these need
to meet clock_settime() requirements of valid values.


Thanks,
pq

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