drm/radeon: add a force flush to delay work when radeon

drm/radeon: add a force flush to delay work when radeon

Although radeon card fence and wait for gpu to finish processing current batch rings,
there is still a corner case that radeon lockup work queue may not be fully flushed,
and meanwhile the radeon_suspend_kms() function has called pci_set_power_state() to
put device in D3hot state.
Per PCI spec rev 4.0 on 5.3.1.4.1 D3hot State.
> Configuration and Message requests are the only TLPs accepted by a Function in
> the D3hot state. All other received Requests must be handled as Unsupported Requests,
> and all received Completions may optionally be handled as Unexpected Completions.
This issue will happen in following logs:
Unable to handle kernel paging request at virtual address 00008800e0008010
CPU 0 kworker/0:3(131): Oops 0
pc = [<ffffffff811bea5c>]  ra = [<ffffffff81240844>]  ps = 0000 Tainted: G        W
pc is at si_gpu_check_soft_reset+0x3c/0x240
ra is at si_dma_is_lockup+0x34/0xd0
v0 = 0000000000000000  t0 = fff08800e0008010  t1 = 0000000000010000
t2 = 0000000000008010  t3 = fff00007e3c00000  t4 = fff00007e3c00258
t5 = 000000000000ffff  t6 = 0000000000000001  t7 = fff00007ef078000
s0 = fff00007e3c016e8  s1 = fff00007e3c00000  s2 = fff00007e3c00018
s3 = fff00007e3c00000  s4 = fff00007fff59d80  s5 = 0000000000000000
s6 = fff00007ef07bd98
a0 = fff00007e3c00000  a1 = fff00007e3c016e8  a2 = 0000000000000008
a3 = 0000000000000001  a4 = 8f5c28f5c28f5c29  a5 = ffffffff810f4338
t8 = 0000000000000275  t9 = ffffffff809b66f8  t10 = ff6769c5d964b800
t11= 000000000000b886  pv = ffffffff811bea20  at = 0000000000000000
gp = ffffffff81d89690  sp = 00000000aa814126
Disabling lock debugging due to kernel taint
Trace:
[<ffffffff81240844>] si_dma_is_lockup+0x34/0xd0
[<ffffffff81119610>] radeon_fence_check_lockup+0xd0/0x290
[<ffffffff80977010>] process_one_work+0x280/0x550
[<ffffffff80977350>] worker_thread+0x70/0x7c0
[<ffffffff80977410>] worker_thread+0x130/0x7c0
[<ffffffff80982040>] kthread+0x200/0x210
[<ffffffff809772e0>] worker_thread+0x0/0x7c0
[<ffffffff80981f8c>] kthread+0x14c/0x210
[<ffffffff80911658>] ret_from_kernel_thread+0x18/0x20
[<ffffffff80981e40>] kthread+0x0/0x210
 Code: ad3e0008  43f0074a  ad7e0018  ad9e0020  8c3001e8  40230101
 <88210000> 4821ed21
So force lockup work queue flush to fix this problem.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Zhenneng Li <lizhenneng@kylinos.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>