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commitb846350aa2upstream. If there's support for another console device (such as a TTY serial), the kernel occasionally panics during boot. The panic message and a relevant snippet of the call stack is as follows: Unable to handle kernel NULL pointer dereference at virtual address 000000000000000 Call trace: drm_crtc_handle_vblank+0x10/0x30 (P) decon_irq_handler+0x88/0xb4 [...] Otherwise, the panics don't happen. This indicates that it's some sort of race condition. Add a check to validate if the drm device can handle vblanks before calling drm_crtc_handle_vblank() to avoid this. Cc: stable@vger.kernel.org Fixes:96976c3d9a("drm/exynos: Add DECON driver") Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org> Signed-off-by: Inki Dae <inki.dae@samsung.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>