sun4i-drm on A20 barf

root@(none):~/drm/tests/modetest# ./modetest -M sun4i-drm -s 8:30:640x480
setting mode 640x480-60Hz@XR24 on connectors 30, crtc 28
[  611.264968] Unable to handle kernel NULL pointer dereference at virtual address 00000001
[  611.277947] pgd = edd50000
[  611.280657] [00000001] *pgd=7fdde835
[  611.284257] Internal error: Oops: 17 [#1] SMP ARM
[  611.288955] Modules linked in:
[  611.292016] CPU: 1 PID: 2462 Comm: lt-modetest Not tainted 4.11.0-rc1-next-20170310-00171-gee9a723dbfa0 #21
[  611.301740] Hardware name: Allwinner sun7i (A20) Family
[  611.306960] task: ef059500 task.stack: ef088000
[  611.311498] PC is at sun4i_tcon1_mode_set+0x18/0x2ac
[  611.316461] LR is at sun4i_hdmi_mode_set+0x20/0x174
[  611.321335] pc : [<c04084e0>]    lr : [<c040aa48>]    psr: a0000013
[  611.321335] sp : ef089d28  ip : ef096780  fp : eebb9c14
[  611.332796] r10: eebb9cdc  r9 : c0a43e18  r8 : eebb9c00
[  611.338014] r7 : ef354ef8  r6 : ef092798  r5 : ef354ef8  r4 : eebb9cdc
[  611.344532] r3 : 00000000  r2 : eebb9cdc  r1 : ef354ef8  r0 : ef092798
[  611.351053] Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
[  611.358179] Control: 10c5387d  Table: 6dd5006a  DAC: 00000051
[  611.363918] Process lt-modetest (pid: 2462, stack limit = 0xef088210)
[  611.370351] Stack: (0xef089d28 to 0xef08a000)
[  611.374707] 9d20:                   ef0b4410 00000000 eebb9c00 00000000 eebb9cdc ef354ef8
[  611.382876] 9d40: ef092790 ee799e00 eebb9c00 c040aa48 c040aa28 eebf9700 00000000 ef354ef8
[  611.391046] 9d60: ee799e00 c03de984 ef096780 c03dee40 ef0b4410 eebf9700 ef355000 00000000
[  611.399215] 9d80: ef355000 edf4bd00 eebf9b80 ef088000 00000001 c03e12bc 00000001 eebf9700
[  611.407384] 9da0: 00000000 c03e1370 ef355000 eebf9700 00000000 c03e1410 c03e137c eebf9700
[  611.415553] 9dc0: 00000000 ef0b4410 ef089e18 c03e1bb0 c03e1b38 ee799a80 ef0b4410 ef355000
[  611.423723] 9de0: ef354c10 c03f1904 00000001 ef089e88 eebf9b80 ef355000 ef354c10 c03f2228
[  611.431892] 9e00: ef0967c0 00000001 ef0b4410 ee799a8c ee799a80 eebf9b80 ee799a80 ef0b4410
[  611.440061] 9e20: edf4bd00 00000000 00000000 eebf9b80 00000001 00000038 c03cf6d4 00000051
[  611.448230] 9e40: ef089e88 c07373e0 edd40480 00000068 c06864a2 000000a2 ef355000 c03eb474
[  611.456400] 9e60: 0000e200 00000001 c08149b4 ee70fa00 00000000 ef089e88 bed76a30 00000068
[  611.464570] 9e80: c03f1dac ef089e88 00011090 00000000 00000001 0000001c 00000025 00000000
[  611.472739] 9ea0: 00000000 00000000 00000001 00006257 02900280 032002f0 01e00000 01ec01ea
[  611.480908] 9ec0: 0000020d 0000003c 0000000a 00000040 78303436 00303834 00000000 00000000
[  611.489077] 9ee0: 00000000 00000000 00000000 00000000 ef088000 00000000 b6ff06e0 c01f5354
[  611.497246] 9f00: 00000000 0000f9ac b6ff06e0 bed76a30 ee838ae8 edd40540 c06864a2 00000003
[  611.505415] 9f20: ef088000 00000000 00000001 c0208784 00000000 00000000 b6ff06e0 00000039
[  611.513584] 9f40: edec7c00 00000000 ee8381b8 00000002 edec7c08 00000000 b6ff06e0 c01f6990
[  611.521754] 9f60: 00000000 00000000 000b6fef edec7c00 edd40540 bed76a30 edd40540 c06864a2
[  611.529923] 9f80: 00000003 ef088000 00000000 c0209014 bed76a30 c06864a2 00000003 00000036
[  611.538092] 9fa0: c0108404 c0108240 bed76a30 c06864a2 00000003 c06864a2 bed76a30 00000001
[  611.546261] 9fc0: bed76a30 c06864a2 00000003 00000036 00000000 00011008 00011008 00000001
[  611.554431] 9fe0: 0000001c bed76a18 b6fc943f b6f44f6c 00000010 00000003 ffffffff ffffffff
[  611.562618] [<c04084e0>] (sun4i_tcon1_mode_set) from [<c040aa48>] (sun4i_hdmi_mode_set+0x20/0x174)
[  611.571578] [<c040aa48>] (sun4i_hdmi_mode_set) from [<c03de984>] (drm_atomic_helper_commit_modeset_disables+0x384/0x3f8)
[  611.582441] [<c03de984>] (drm_atomic_helper_commit_modeset_disables) from [<c03e12bc>] (drm_atomic_helper_commit_tail+0x18/0x64)
[  611.593994] [<c03e12bc>] (drm_atomic_helper_commit_tail) from [<c03e1370>] (commit_tail+0x68/0x6c)
[  611.602948] [<c03e1370>] (commit_tail) from [<c03e1410>] (drm_atomic_helper_commit+0x94/0xe4)
[  611.611468] [<c03e1410>] (drm_atomic_helper_commit) from [<c03e1bb0>] (drm_atomic_helper_set_config+0x78/0xac)
[  611.621463] [<c03e1bb0>] (drm_atomic_helper_set_config) from [<c03f1904>] (drm_mode_set_config_internal+0x58/0xdc)
[  611.631804] [<c03f1904>] (drm_mode_set_config_internal) from [<c03f2228>] (drm_mode_setcrtc+0x47c/0x4a8)
[  611.641275] [<c03f2228>] (drm_mode_setcrtc) from [<c03eb474>] (drm_ioctl+0x1f8/0x424)
[  611.649102] [<c03eb474>] (drm_ioctl) from [<c0208784>] (do_vfs_ioctl+0x98/0x8f4)
[  611.656494] [<c0208784>] (do_vfs_ioctl) from [<c0209014>] (SyS_ioctl+0x34/0x5c)
[  611.663801] [<c0209014>] (SyS_ioctl) from [<c0108240>] (ret_fast_syscall+0x0/0x3c)
[  611.671366] Code: e5903024 e24dd010 e1a07001 e1a04002 (e5d33001)
[  611.677537] ---[ end trace 834d61f2a2f23618 ]---