[PATCH 2/4] drm/vc4: Use DMA Resv to implement VC4 wait BO IOCTL

[Maíra Canal]

As the BOs used by VC4 have DMA Reservation Objects attached to it,
there is no need to use seqnos wait for the BOs availability. Instead,
we can use `dma_gem_dma_resv_wait()`.

Signed-off-by: Maíra Canal <mcanal at igalia.com>
---
 drivers/gpu/drm/vc4/vc4_drv.h | 10 ++++++++++
 drivers/gpu/drm/vc4/vc4_gem.c | 31 +++++++++++++++++++------------
 2 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 4a078ffd9f82..03ed40ab9a93 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -924,6 +924,16 @@ struct vc4_validated_shader_info {
 						   (Wmax))
 #define wait_for(COND, MS)		_wait_for((COND), (MS) * 1000, 10, 1000)
 
+static inline unsigned long nsecs_to_jiffies_timeout(const u64 n)
+{
+	/* nsecs_to_jiffies64() does not guard against overflow */
+	if ((NSEC_PER_SEC % HZ) != 0 &&
+	    div_u64(n, NSEC_PER_SEC) >= MAX_JIFFY_OFFSET / HZ)
+		return MAX_JIFFY_OFFSET;
+
+	return min_t(u64, MAX_JIFFY_OFFSET, nsecs_to_jiffies64(n) + 1);
+}
+
 /* vc4_bo.c */
 struct drm_gem_object *vc4_create_object(struct drm_device *dev, size_t size);
 struct vc4_bo *vc4_bo_create(struct drm_device *dev, size_t size,
diff --git a/drivers/gpu/drm/vc4/vc4_gem.c b/drivers/gpu/drm/vc4/vc4_gem.c
index 2e5477b1c73a..256af016ade0 100644
--- a/drivers/gpu/drm/vc4/vc4_gem.c
+++ b/drivers/gpu/drm/vc4/vc4_gem.c
@@ -1022,11 +1022,13 @@ int
 vc4_wait_bo_ioctl(struct drm_device *dev, void *data,
 		  struct drm_file *file_priv)
 {
-	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	int ret;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct drm_vc4_wait_bo *args = data;
-	struct drm_gem_object *gem_obj;
-	struct vc4_bo *bo;
+	unsigned long timeout_jiffies =
+		nsecs_to_jiffies_timeout(args->timeout_ns);
+	ktime_t start = ktime_get();
+	u64 delta_ns;
 
 	if (WARN_ON_ONCE(vc4->gen > VC4_GEN_4))
 		return -ENODEV;
@@ -1034,17 +1036,22 @@ vc4_wait_bo_ioctl(struct drm_device *dev, void *data,
 	if (args->pad != 0)
 		return -EINVAL;
 
-	gem_obj = drm_gem_object_lookup(file_priv, args->handle);
-	if (!gem_obj) {
-		DRM_DEBUG("Failed to look up GEM BO %d\n", args->handle);
-		return -EINVAL;
-	}
-	bo = to_vc4_bo(gem_obj);
+	ret = drm_gem_dma_resv_wait(file_priv, args->handle,
+				    true, timeout_jiffies);
 
-	ret = vc4_wait_for_seqno_ioctl_helper(dev, bo->seqno,
-					      &args->timeout_ns);
+	/* Decrement the user's timeout, in case we got interrupted
+	 * such that the ioctl will be restarted.
+	 */
+	delta_ns = ktime_to_ns(ktime_sub(ktime_get(), start));
+	if (delta_ns < args->timeout_ns)
+		args->timeout_ns -= delta_ns;
+	else
+		args->timeout_ns = 0;
+
+	/* Asked to wait beyond the jiffy/scheduler precision? */
+	if (ret == -ETIME && args->timeout_ns)
+		ret = -EAGAIN;
 
-	drm_gem_object_put(gem_obj);
 	return ret;
 }
 
-- 
2.47.1