Most of the kms_frontbuffer_tracking tests disables the feature being
tested, draw, get the CRC then enable the feature, draw again, get the
CRC and check if it matches.
Some times it is able to do that with a fastset, so
intel_pre_plane_update() is executed but intel_fbc_can_flip_nuke() was
not checking if FBC is now enabled in this CRTC leaving FBC active and
causing the warning bellow in __intel_fbc_disable()

[IGT] kms_frontbuffer_tracking: starting subtest fbc-1p-pri-indfb-multidraw
Setting dangerous option enable_fbc - tainting kernel
i915 0000:00:02.0: [drm:i915_edp_psr_debug_set [i915]] Setting PSR debug to f
i915 0000:00:02.0: [drm:intel_psr_debug_set [i915]] Invalid debug mask f
i915 0000:00:02.0: [drm:i915_edp_psr_debug_set [i915]] Setting PSR debug to 1
i915 0000:00:02.0: [drm:intel_atomic_check [i915]] [CONNECTOR:215:eDP-1] Limiting display bpp to 24 instead of EDID bpp 24, requested bpp 36, max platform bpp 36
[drm:intel_dp_compute_config [i915]] DP link computation with max lane count 2 max rate 270000 max bpp 24 pixel clock 138120KHz
[drm:intel_dp_compute_config [i915]] Force DSC en = 0
[drm:intel_dp_compute_config [i915]] DP lane count 2 clock 270000 bpp 24
[drm:intel_dp_compute_config [i915]] DP link rate required 414360 available 540000
i915 0000:00:02.0: [drm:intel_atomic_check [i915]] hw max bpp: 24, pipe bpp: 24, dithering: 0
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] [CRTC:91:pipe A] enable: yes [fastset]
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] active: yes, output_types: EDP (0x100), output format: RGB
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] cpu_transcoder: EDP, pipe bpp: 24, dithering: 0
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] dp m_n: lanes: 2; gmch_m: 6436858, gmch_n: 8388608, link_m: 268202, link_n: 524288, tu: 64
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] audio: 0, infoframes: 0, infoframes enabled: 0x0
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] requested mode:
[drm:drm_mode_debug_printmodeline] Modeline "1920x1080": 60 138120 1920 1968 2018 2052 1080 1084 1086 1122 0x48 0xa
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] adjusted mode:
[drm:drm_mode_debug_printmodeline] Modeline "1920x1080": 60 138120 1920 1968 2018 2052 1080 1084 1086 1122 0x48 0xa
[drm:intel_dump_pipe_config [i915]] crtc timings: 138120 1920 1968 2018 2052 1080 1084 1086 1122, type: 0x48 flags: 0xa
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] port clock: 270000, pipe src size: 1920x1080, pixel rate 138120
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] linetime: 119, ips linetime: 0
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] num_scalers: 2, scaler_users: 0x0, scaler_id: -1
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] pch pfit: pos: 0x00000000, size: 0x00000000, disabled, force thru: no
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] ips: 0, double wide: 0
[drm:icl_dump_hw_state [i915]] dpll_hw_state: cfgcr0: 0x1c001a5, cfgcr1: 0x8b, mg_refclkin_ctl: 0x0, hg_clktop2_coreclkctl1: 0x0, mg_clktop2_hsclkctl: 0x0, mg_pll_div0: 0x0, mg_pll_div2: 0x0, mg_pll_lf: 0x0, mg_pll_frac_lock: 0x0, mg_pll_ssc: 0x0, mg_pll_bias: 0x0, mg_pll_tdc_coldst_bias: 0x0
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] csc_mode: 0x0 gamma_mode: 0x0 gamma_enable: 0 csc_enable: 0
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] MST master transcoder: <invalid>
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] [PLANE:31:plane 1A] fb: [FB:262] 1920x1080 format = XR24 little-endian (0x34325258), visible: yes
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] 	rotation: 0x1, scaler: -1
i915 0000:00:02.0: [drm:intel_dump_pipe_config [i915]] 	src: 1920.000000x1080.000000+0.000000+0.000000 dst: 1920x1080+0+0
i915 0000:00:02.0: [drm:intel_psr_disable_locked [i915]] Disabling PSR1
i915 0000:00:02.0: [drm:intel_ddi_update_pipe [i915]] Panel doesn't support DRRS
------------[ cut here ]------------
i915 0000:00:02.0: drm_WARN_ON(fbc->active)
WARNING: CPU: 4 PID: 1175 at drivers/gpu/drm/i915/display/intel_fbc.c:973 __intel_fbc_disable+0xa5/0x130 [i915]
Modules linked in: snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic i915 mei_hdcp x86_pkg_temp_thermal coretemp crct10dif_pclmul snd_hda_intel crc32_pclmul snd_intel_dspcfg snd_hda_codec ghash_clmulni_intel snd_hwdep snd_hda_core cdc_ether e1000e usbnet mii snd_pcm ptp mei_me pps_core mei thunderbolt intel_lpss_pci prime_numbers
CPU: 4 PID: 1175 Comm: kms_frontbuffer Tainted: G     U            5.5.0-CI-Trybot_5651+ #1
Hardware name: Intel Corporation Ice Lake Client Platform/IceLake U DDR4 SODIMM PD RVP TLC, BIOS ICLSFWR1.R00.3234.A01.1906141750 06/14/2019
RIP: 0010:__intel_fbc_disable+0xa5/0x130 [i915]
Code: 8b 67 50 4d 85 e4 0f 84 8f 00 00 00 e8 44 33 30 e1 48 c7 c1 72 f6 4c a0 4c 89 e2 48 89 c6 48 c7 c7 42 f6 4c a0 e8 0b 9d ce e0 <0f> 0b eb 90 48 8b 7b 18 4c 8b 67 50 4d 85 e4 74 6d e8 15 33 30 e1
RSP: 0018:ffffc90000613b68 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff8884799d0000 RCX: 0000000000000006
RDX: 0000000000001905 RSI: ffff888495dac970 RDI: ffffffff823731a1
RBP: ffff88847c05d000 R08: ffff888495dac970 R09: 0000000000000000
R10: ffffc90000613b88 R11: 0000000000000000 R12: ffff88849bba7e40
R13: ffff8884799d0000 R14: ffff888498564000 R15: 0000000000000000
FS:  00007f8157f08300(0000) GS:ffff8884a0000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffdbfea2eb8 CR3: 000000049d1cc001 CR4: 0000000000760ee0
PKRU: 55555554
Call Trace:
 intel_fbc_disable+0x4a/0x50 [i915]
 intel_update_crtc+0x12c/0x1d0 [i915]
 skl_commit_modeset_enables+0x14d/0x600 [i915]
 intel_atomic_commit_tail+0x30d/0x1480 [i915]
 ? queue_work_on+0x31/0x70
 ? intel_atomic_commit_ready+0x3f/0x48 [i915]
 ? __i915_sw_fence_complete+0x1a0/0x250 [i915]
 intel_atomic_commit+0x312/0x390 [i915]
 intel_psr_fastset_force+0x119/0x150 [i915]
 i915_edp_psr_debug_set+0x53/0x70 [i915]
 simple_attr_write+0xb0/0xd0
 full_proxy_write+0x51/0x80
 vfs_write+0xb9/0x1d0
 ksys_write+0x9f/0xe0
 do_syscall_64+0x4f/0x220
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f8157240281
Code: c3 0f 1f 84 00 00 00 00 00 48 8b 05 59 8d 20 00 c3 0f 1f 84 00 00 00 00 00 8b 05 8a d1 20 00 85 c0 75 16 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 57 f3 c3 0f 1f 44 00 00 41 54 55 49 89 d4 53
RSP: 002b:00007ffdbfea59d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f8157240281
RDX: 0000000000000003 RSI: 00007f8157901152 RDI: 0000000000000008
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f8157901152
R13: 0000000000000008 R14: 00005589d298dce0 R15: 0000000000000000
irq event stamp: 55208
hardirqs last  enabled at (55207): [<ffffffff8112f3fc>] vprintk_emit+0xcc/0x330
hardirqs last disabled at (55208): [<ffffffff81001ca0>] trace_hardirqs_off_thunk+0x1a/0x1c
softirqs last  enabled at (54926): [<ffffffff81e00385>] __do_softirq+0x385/0x47f
softirqs last disabled at (54915): [<ffffffff810ba15a>] irq_exit+0xba/0xc0
---[ end trace afa50c52e5a512bb ]---
[drm:__intel_fbc_disable [i915]] Disabling FBC on pipe A
i915 0000:00:02.0: [drm:verify_connector_state [i915]] [CONNECTOR:215:eDP-1]
i915 0000:00:02.0: [drm:intel_atomic_commit_tail [i915]] [CRTC:91:pipe A]
[drm:intel_ddi_get_config [i915]] [ENCODER:214:DDI A] Fec status: 0
i915 0000:00:02.0: [drm:verify_single_dpll_state.isra.150 [i915]] DPLL 0

v2:
using intel_fbc_can_enable() instead of crtc_state->enable_fbc (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200306185833.53984-1-jose.souza@intel.com