[PATCH v2 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 <mca...@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 1021f45cb53c..4037c65eb269 100644
--- a/drivers/gpu/drm/vc4/vc4_gem.c
+++ b/drivers/gpu/drm/vc4/vc4_gem.c
@@ -1017,11 +1017,13 @@ 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;
@@ -1029,17 +1031,22 @@ 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