drm/rockchip: fix race with kms hotplug and fbdev
According to the kerneldoc[0], should do fbdev setup before calling
drm_kms_helper_poll_init(), otherwise, Kms hotplug event may race
into fbdev helper initial, and fb_helper->dev may be NULL pointer,
that would cause the bug:
[ 0.735411] [
00000200] *pgd=
00000000f6ffe003, *pud=
00000000f6ffe003, *pmd=
0000000000000000
[ 0.736156] Internal error: Oops:
96000005 [#1] PREEMPT SMP
[ 0.736648] Modules linked in:
[ 0.736930] CPU: 2 PID: 20 Comm: kworker/2:0 Not tainted 4.4.41 #20
[ 0.737480] Hardware name: Rockchip RK3399 Board rev2 (BOX) (DT)
[ 0.738020] Workqueue: events cdn_dp_pd_event_work
[ 0.738447] task:
ffffffc0f21f3100 ti:
ffffffc0f2218000 task.ti:
ffffffc0f2218000
[ 0.739109] PC is at mutex_lock+0x14/0x44
[ 0.739469] LR is at drm_fb_helper_hotplug_event+0x30/0x114
[ 0.756253] [<
ffffff8008a344f4>] mutex_lock+0x14/0x44
[ 0.756260] [<
ffffff8008445708>] drm_fb_helper_hotplug_event+0x30/0x114
[ 0.756271] [<
ffffff8008473c84>] rockchip_drm_output_poll_changed+0x18/0x20
[ 0.756280] [<
ffffff8008439fcc>] drm_kms_helper_hotplug_event+0x28/0x34
[ 0.756286] [<
ffffff800846c444>] cdn_dp_pd_event_work+0x394/0x3c4
[ 0.756295] [<
ffffff80080b2b38>] process_one_work+0x218/0x3e0
[ 0.756302] [<
ffffff80080b3538>] worker_thread+0x2e8/0x404
[ 0.756308] [<
ffffff80080b7e70>] kthread+0xe8/0xf0
[ 0.756316] [<
ffffff8008082690>] ret_from_fork+0x10/0x40
[0]: https://01.org/linuxgraphics/gfx-docs/drm/gpu/drm-kms-helpers.html
Signed-off-by: Mark Yao <mark.yao@rock-chips.com>
Reviewed-by: Sandy huang <sandy.huang@rock-chips.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1501575103-20136-1-git-send-email-mark.yao@rock-chips.com