drm/i915: Don't oops in dumb_create ioctl if we have no crtcs

commit 8ac495f624a42809000255955be406f6a8a74b55 upstream.

Make sure we have a crtc before probing its primary plane's
max stride. Initially I thought we can't get this far without
crtcs, but looks like we can via the dumb_create ioctl.

Not sure if we shouldn't disable dumb buffer support entirely
when we have no crtcs, but that would require some amount of work
as the only thing currently being checked is dev->driver->dumb_create
which we'd have to convert to some device specific dynamic thing.

Cc: stable@vger.kernel.org
Reported-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Fixes: aa5ca8b7421c ("drm/i915: Align dumb buffer stride to 4k to allow for gtt remapping")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191106172349.11987-1-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
(cherry picked from commit baea9ffe64200033499a4955f431e315bb807899)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
(cherry picked from commit aeec766133f99d45aad60d650de50fb382104d95)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index dae45b6a35b771ffbce751f30f767e4732b3c738..5c8c11deb85737265a58b27e8275fd7fe67d515d 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -2519,6 +2519,9 @@ u32 intel_plane_fb_max_stride(struct drm_i915_private *dev_priv,
         * the highest stride limits of them all.
         */
        crtc = intel_get_crtc_for_pipe(dev_priv, PIPE_A);
+       if (!crtc)
+               return 0;
+
        plane = to_intel_plane(crtc->base.primary);
 
        return plane->max_stride(plane, pixel_format, modifier,