The -modesetting ddx has a totally broken idea of how atomic works: - doesn't disable old connectors, assuming they get auto-disable like with the legacy setcrtc - assumes ASYNC_FLIP is wired through for the atomic ioctl - not a single call to TEST_ONLY
Iow the implementation is a 1:1 translation of legacy ioctls to atomic, which is a) broken b) pointless.
We already have bugs in both i915 and amdgpu-DC where this prevents us from enabling neat features.
If anyone ever cares about atomic in X we can easily add a new atomic level (req->value == 2) for X to get back the shiny toys.
Since these broken versions of -modesetting have been shipping, there's really no other way to get out of this bind.
v2: - add an informational dmesg output (Rob, Ajax) - reorder after the DRIVER_ATOMIC check to avoid useless noise (Ilia) - allow req->value > 2 so that X can do another attempt at atomic in the future
Cc: Ilia Mirkin imirkin@alum.mit.edu References: https://gitlab.freedesktop.org/xorg/xserver/issues/629 References: https://gitlab.freedesktop.org/xorg/xserver/merge_requests/180 References: abbc0697d5fb ("drm/fb: revert the i915 Actually configure untiled displays from master") Cc: Maarten Lankhorst maarten.lankhorst@linux.intel.com Reviewed-by: Maarten Lankhorst maarten.lankhorst@linux.intel.com (v1) Reviewed-by: Nicholas Kazlauskas nicholas.kazlauskas@amd.com (v1) Cc: Michel Dänzer michel@daenzer.net Cc: Alex Deucher alexdeucher@gmail.com Cc: Adam Jackson ajax@redhat.com Acked-by: Adam Jackson ajax@redhat.com Cc: Sean Paul sean@poorly.run Cc: David Airlie airlied@linux.ie Cc: Rob Clark robdclark@gmail.com Acked-by: Rob Clark robdclark@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Daniel Vetter daniel.vetter@intel.com --- drivers/gpu/drm/drm_ioctl.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index 2c120c58f72d..56aa8bbb3a8c 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -336,7 +336,12 @@ drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv) case DRM_CLIENT_CAP_ATOMIC: if (!drm_core_check_feature(dev, DRIVER_ATOMIC)) return -EOPNOTSUPP; - if (req->value > 1) + /* The modesetting DDX has a totally broken idea of atomic. */ + if (strstr(current->comm, "X") && req->value == 1) { + pr_info("broken atomic modeset userspace detected, disabling atomic\n"); + return -EOPNOTSUPP; + } + if (req->value > 2) return -EINVAL; file_priv->atomic = req->value; file_priv->universal_planes = req->value;