[Mesa-dev] [PATCH 2/2 v4] intel: wait render timeout implementation

[Ben Widawsky]

int drm_intel_gem_bo_wait(drm_intel_bo *bo, uint64_t timeout_ns)

This should bump the libdrm version. We're waiting for context support
so we can do both features in one bump.

v2: don't return remaining timeout amount
use get param and fallback for older kernels

v3: only doing getparam at init
prototypes now have a signed input value

v4: update comments
fall back to correct polling behavior with new userspace and old kernel

Cc: Eric Anholt <eric at anholt.net>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 intel/intel_bufmgr.h     |    1 +
 intel/intel_bufmgr_gem.c |   51 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/intel/intel_bufmgr.h b/intel/intel_bufmgr.h
index c197abc..fa6c4dd 100644
--- a/intel/intel_bufmgr.h
+++ b/intel/intel_bufmgr.h
@@ -184,6 +184,7 @@ int drm_intel_get_pipe_from_crtc_id(drm_intel_bufmgr *bufmgr, int crtc_id);
 
 int drm_intel_get_aperture_sizes(int fd, size_t *mappable, size_t *total);
 int drm_intel_bufmgr_gem_get_devid(drm_intel_bufmgr *bufmgr);
+int drm_intel_gem_bo_wait(drm_intel_bo *bo, int64_t timeout_ns);
 
 /* drm_intel_bufmgr_fake.c */
 drm_intel_bufmgr *drm_intel_bufmgr_fake_init(int fd,
diff --git a/intel/intel_bufmgr_gem.c b/intel/intel_bufmgr_gem.c
index b776d2f..f8e3706 100644
--- a/intel/intel_bufmgr_gem.c
+++ b/intel/intel_bufmgr_gem.c
@@ -119,6 +119,7 @@ typedef struct _drm_intel_bufmgr_gem {
 	unsigned int has_blt : 1;
 	unsigned int has_relaxed_fencing : 1;
 	unsigned int has_llc : 1;
+	unsigned int has_wait_timeout : 1;
 	unsigned int bo_reuse : 1;
 	unsigned int no_exec : 1;
 	bool fenced_relocs;
@@ -1479,6 +1480,52 @@ drm_intel_gem_bo_wait_rendering(drm_intel_bo *bo)
 }
 
 /**
+ * Waits on a BO for the given amount of time.
+ *
+ * @bo: buffer object to wait for
+ * @timeout_ns: amount of time to wait in nanoseconds.
+ *   If value is less than 0, an infinite wait will occur.
+ *
+ * Returns 0 if the wait was successful ie. the last batch referencing the
+ * object has completed within the allotted time. Otherwise some negative return
+ * value describes the error.
+ *
+ * Similar to drm_intel_gem_bo_wait_rendering except a timeout parameter allows
+ * the operation to give up after a certain amount of time. Another subtle
+ * difference is the internal locking semantics are different (this variant does
+ * not hold the lock for the duration of the wait). This makes the wait subject
+ * to a larger userspace race window.
+ *
+ * The implementation shall wait until the object is no longer actively
+ * referenced within a batch buffer at the time of the call. The wait will
+ * not guarantee that the buffer is re-issued via another thread, or an flinked
+ * handle. Userspace must make sure this race does not occur if such precision
+ * is important.
+ */
+int drm_intel_gem_bo_wait(drm_intel_bo *bo, int64_t timeout_ns)
+{
+	drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *) bo->bufmgr;
+	drm_intel_bo_gem *bo_gem = (drm_intel_bo_gem *) bo;
+	struct drm_i915_gem_wait wait;
+
+	if (!bufmgr_gem->has_wait_timeout) {
+		DBG("%s:%d: Timed wait is not supported. Falling back to "
+		    "infinite wait\n", __FILE__, __LINE__);
+		if (timeout_ns) {
+			drm_intel_gem_bo_wait_rendering(bo);
+			return 0;
+		} else {
+			return drm_intel_gem_bo_busy(bo);
+		}
+	}
+
+	wait.bo_handle = bo_gem->gem_handle;
+	wait.timeout_ns = timeout_ns;
+	wait.flags = 0;
+	return drmIoctl(bufmgr_gem->fd, DRM_IOCTL_I915_GEM_WAIT, &wait);
+}
+
+/**
  * Sets the object to the GTT read and possibly write domain, used by the X
  * 2D driver in the absence of kernel support to do drm_intel_gem_bo_map_gtt().
  *
@@ -2898,6 +2945,10 @@ drm_intel_bufmgr_gem_init(int fd, int batch_size)
 	ret = drmIoctl(bufmgr_gem->fd, DRM_IOCTL_I915_GETPARAM, &gp);
 	bufmgr_gem->has_relaxed_fencing = ret == 0;
 
+	gp.param = I915_PARAM_HAS_WAIT_TIMEOUT;
+	ret = drmIoctl(bufmgr_gem->fd, DRM_IOCTL_I915_GETPARAM, &gp);
+	bufmgr_gem->has_wait_timeout = ret == 0;
+
 	gp.param = I915_PARAM_HAS_LLC;
 	ret = drmIoctl(bufmgr_gem->fd, DRM_IOCTL_I915_GETPARAM, &gp);
 	if (ret != 0) {
-- 
1.7.10.3