Atomic does not let us have multiple requests in flight at once; if we
don't synchronise with the request completion on the CPU side, we can
get -EBUSY from the atomic commit.
We already have everything required to do this, namely the out-fence
from the last commit. Block on that with a CPU-side wait before we call
atomic commit, to make sure we'll never attempt to queue an atomic
commit before the previous one has completed.
Signed-off-by: Daniel Stone <dani...@collabora.com>
---
common.c | 1 +
common.h | 1 +
drm-atomic.c | 21 ++++++++++++++++++++-
3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/common.c b/common.c
index bf2f78e..a2cf630 100644
--- a/common.c
+++ b/common.c
@@ -155,6 +155,7 @@ int init_egl(struct egl *egl, const struct gbm *gbm)
get_proc_dpy(eglCreateSyncKHR, "EGL_KHR_fence_sync");
get_proc_dpy(eglDestroySyncKHR, "EGL_KHR_fence_sync");
get_proc_dpy(eglWaitSyncKHR, "EGL_KHR_fence_sync");
+ get_proc_dpy(eglClientWaitSyncKHR, "EGL_KHR_fence_sync");
get_proc_dpy(eglDupNativeFenceFDANDROID,
"EGL_ANDROID_native_fence_sync");
printf("Using display %p with EGL version %d.%d\n",
diff --git a/common.h b/common.h
index 639bd87..0acf4c0 100644
--- a/common.h
+++ b/common.h
@@ -79,6 +79,7 @@ struct egl {
PFNEGLCREATESYNCKHRPROC eglCreateSyncKHR;
PFNEGLDESTROYSYNCKHRPROC eglDestroySyncKHR;
PFNEGLWAITSYNCKHRPROC eglWaitSyncKHR;
+ PFNEGLCLIENTWAITSYNCKHRPROC eglClientWaitSyncKHR;
PFNEGLDUPNATIVEFENCEFDANDROIDPROC eglDupNativeFenceFDANDROID;
void (*draw)(unsigned i);
diff --git a/drm-atomic.c b/drm-atomic.c
index 0f3c4f2..65caacd 100644
--- a/drm-atomic.c
+++ b/drm-atomic.c
@@ -210,6 +210,7 @@ static int atomic_run(const struct gbm *gbm, const struct
egl *egl)
if (drm.kms_out_fence_fd != -1) {
kms_fence = create_fence(egl, drm.kms_out_fence_fd);
+ assert(kms_fence);
/* driver now has ownership of the fence fd: */
drm.kms_out_fence_fd = -1;
@@ -220,7 +221,6 @@ static int atomic_run(const struct gbm *gbm, const struct
egl *egl)
* the buffer that is still on screen.
*/
egl->eglWaitSyncKHR(egl->display, kms_fence, 0);
- egl->eglDestroySyncKHR(egl->display, kms_fence);
}
egl->draw(i++);
@@ -229,6 +229,7 @@ static int atomic_run(const struct gbm *gbm, const struct
egl *egl)
* signaled when gpu rendering done
*/
gpu_fence = create_fence(egl, EGL_NO_NATIVE_FENCE_FD_ANDROID);
+ assert(gpu_fence);
eglSwapBuffers(egl->display, egl->surface);
@@ -246,6 +247,24 @@ static int atomic_run(const struct gbm *gbm, const struct
egl *egl)
return -1;
}
+ if (kms_fence) {
+ EGLint status;
+
+ /* Wait on the CPU side for the _previous_ commit to
+ * complete before we post the flip through KMS, as
+ * atomic will reject the commit if we post a new one
+ * whilst the previous one is still pending.
+ */
+ do {
+ status = egl->eglClientWaitSyncKHR(egl->display,
+ kms_fence,
+ 0,
+
EGL_FOREVER_KHR);
+ } while (status != EGL_CONDITION_SATISFIED_KHR);
+
+ egl->eglDestroySyncKHR(egl->display, kms_fence);
+ }
+
/*
* Here you could also update drm plane layers if you want
* hw composition
--
2.12.2
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