From: Daniel Vetter <daniel.vetter@ffwll.ch> commit 26b1d3b527e7bf3e24b814d617866ac5199ce68d upstream. 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 v3: Go with paranoid, insist that the X should be first (suggested by Rob) 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> Link: https://patchwork.freedesktop.org/patch/msgid/20190905185318.31363-1-daniel.... Cc: Yves-Alexis Perez <corsac@debian.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- 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 ba129b6..b92682f 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -321,7 +321,12 @@ static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_ case DRM_CLIENT_CAP_ATOMIC: if (!drm_core_check_feature(dev, DRIVER_ATOMIC)) return -EINVAL; - if (req->value > 1) + /* The modesetting DDX has a totally broken idea of atomic. */ + if (current->comm[0] == '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; -- 1.8.3