From 497ab787e5ab56c630014a20b43bfab16e3b43aa Mon Sep 17 00:00:00 2001 From: Daniel Stone Date: Mon, 17 Apr 2017 13:11:13 +0100 Subject: atomic: Use CPU-side KMS fence synchronisation 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 Reviewed-by: Emil Velikov --- drm-atomic.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) (limited to 'drm-atomic.c') 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 -- cgit v1.2.1