drm/bridge: megachips: Ensure both bridges are probed before registration

drm/bridge: megachips: Ensure both bridges are probed before registration

In the configuration used by the b850v3, the STDP2690 is used to read EDID
data whilst it's the STDP4028 which can detect when monitors are connected.

This can result in problems at boot with monitors connected when the
STDP4028 is probed first, a monitor is detected and an attempt is made to
read the EDID data before the STDP2690 has probed:

[    3.795721] Unable to handle kernel NULL pointer dereference at virtual address 00000018
[    3.803845] pgd = (ptrval)
[    3.806581] [00000018] *pgd=00000000
[    3.810180] Internal error: Oops: 5 [#1] SMP ARM
[    3.814813] Modules linked in:
[    3.817879] CPU: 0 PID: 64 Comm: kworker/u4:1 Not tainted 5.15.0 #1
[    3.824161] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
[    3.830705] Workqueue: events_unbound deferred_probe_work_func
[    3.836565] PC is at stdp2690_get_edid+0x44/0x19c
[    3.841286] LR is at ge_b850v3_lvds_get_modes+0x2c/0x5c
[    3.846526] pc : [<805eae10>]    lr : [<805eb138>]    psr: 80000013
[    3.852802] sp : 81c359d0  ip : 7dbb550b  fp : 81c35a1c
[    3.858037] r10: 81c73840  r9 : 81c73894  r8 : 816d9800
[    3.863270] r7 : 00000000  r6 : 81c34000  r5 : 00000000  r4 : 810c35f0
[    3.869808] r3 : 80e3e294  r2 : 00000080  r1 : 00000cc0  r0 : 81401180
[    3.876349] Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
[    3.883499] Control: 10c5387d  Table: 1000404a  DAC: 00000051
[    3.889254] Register r0 information: slab kmem_cache start 81401180 pointer offset 0
[    3.897034] Register r1 information: non-paged memory
[    3.902097] Register r2 information: non-paged memory
[    3.907160] Register r3 information: non-slab/vmalloc memory
[    3.912832] Register r4 information: non-slab/vmalloc memory
[    3.918503] Register r5 information: NULL pointer
[    3.923217] Register r6 information: non-slab/vmalloc memory
[    3.928887] Register r7 information: NULL pointer
[    3.933601] Register r8 information: slab kmalloc-1k start 816d9800 pointer offset 0 size 1024
[    3.942244] Register r9 information: slab kmalloc-2k start 81c73800 pointer offset 148 size 2048
[    3.951058] Register r10 information: slab kmalloc-2k start 81c73800 pointer offset 64 size 2048
[    3.959873] Register r11 information: non-slab/vmalloc memory
[    3.965632] Register r12 information: non-paged memory
[    3.970781] Process kworker/u4:1 (pid: 64, stack limit = 0x(ptrval))
[    3.977148] Stack: (0x81c359d0 to 0x81c36000)
[    3.981517] 59c0:                                     80b2b668 80b2b5bc 000002e2 0000034e
[    3.989712] 59e0: 81c35a8c 816d98e8 81c35a14 7dbb550b 805bfcd0 810c35f0 81c73840 824addc0
[    3.997906] 5a00: 00001000 816d9800 81c73894 81c73840 81c35a34 81c35a20 805eb138 805eadd8
[    4.006099] 5a20: 810c35f0 00000045 81c35adc 81c35a38 80594188 805eb118 80d7c788 80dd1848
[    4.014292] 5a40: 00000000 81c35a50 80dca950 811194d3 80dca7c4 80dca944 80dca91c 816d9800
[    4.022485] 5a60: 81c34000 81c760a8 816d9800 80c58c98 810c35f0 816d98e8 00001000 00001000
[    4.030678] 5a80: 00000000 00000000 8017712c 81c60000 00000002 00000001 00000000 00000000
[    4.038870] 5aa0: 816d9900 816d9900 00000000 7dbb550b 805c700c 00000008 826282c8 826282c8
[    4.047062] 5ac0: 00001000 81e1ce40 00001000 00000002 81c35bf4 81c35ae0 805d9694 80593fc0
[    4.055255] 5ae0: 8017a970 80179ad8 00000179 00000000 81c35bcc 81c35b00 80177108 8017a950
[    4.063447] 5b00: 00000000 81c35b10 81c34000 00000000 81004fd8 81010a38 00000000 00000059
[    4.071639] 5b20: 816d98d4 81fbb718 00000013 826282c8 8017a940 81c35b40 81134448 00000400
[    4.079831] 5b40: 00000178 00000000 e063b9c1 00000000 c2000049 00000040 00000000 00000008
[    4.088024] 5b60: 82628300 82628380 00000000 00000000 81c34000 00000000 81fbb700 82628340
[    4.096216] 5b80: 826283c0 00001000 00000000 00000010 816d9800 826282c0 801766f8 00000000
[    4.104408] 5ba0: 00000000 81004fd8 00000049 00000000 00000000 00000001 80dcf940 80178de4
[    4.112601] 5bc0: 81c35c0c 7dbb550b 80178de4 81fbb700 00000010 00000010 810c35f4 81e1ce40
[    4.120793] 5be0: 81c40908 0000000c 81c35c64 81c35bf8 805a7f18 805d94a0 81c35c3c 816d9800
[    4.128985] 5c00: 00000010 81c34000 81c35c2c 81c35c18 8012fce0 805be90c 81c35c3c 81c35c28
[    4.137178] 5c20: 805be90c 80173210 81fbb600 81fbb6b4 81c35c5c 7dbb550b 81c35c64 81fbb700
[    4.145370] 5c40: 816d9800 00000010 810c35f4 81e1ce40 81c40908 0000000c 81c35c84 81c35c68
[    4.153565] 5c60: 805a8c78 805a7ed0 816d9800 81fbb700 00000010 00000000 81c35cac 81c35c88
[    4.161758] 5c80: 805a8dc4 805a8b68 816d9800 00000000 816d9800 00000000 8179f810 810c42d0
[    4.169950] 5ca0: 81c35ccc 81c35cb0 805e47b0 805a8d18 824aa240 81e1ea80 81c40908 81126b60
[    4.178144] 5cc0: 81c35d14 81c35cd0 8060db1c 805e46cc 81c35d14 81c35ce0 80dd90f8 810c4d58
[    4.186338] 5ce0: 80dd90dc 81fe9740 fffffffe 81fe9740 81e1ea80 00000000 810c4d6c 80c4b95c
[    4.194531] 5d00: 80dd9a3c 815c6810 81c35d34 81c35d18 8060dc9c 8060d8fc 8246b440 815c6800
[    4.202724] 5d20: 815c6810 eefd8e00 81c35d44 81c35d38 8060dd80 8060dbec 81c35d6c 81c35d48
[    4.210918] 5d40: 805e98a4 8060dd70 00000000 815c6810 810c45b0 81126e90 81126e90 80dd9a3c
[    4.219112] 5d60: 81c35d8c 81c35d70 80619574 805e9808 815c6810 00000000 810c45b0 81126e90
[    4.227305] 5d80: 81c35db4 81c35d90 806168dc 80619514 80625df0 80623c80 815c6810 810c45b0
[    4.235498] 5da0: 81c35e6c 815c6810 81c35dec 81c35db8 80616d04 80616800 81c35de4 81c35dc8
[    4.243691] 5dc0: 808382b0 80b2f444 8116e310 8116e314 81c35e6c 815c6810 00000003 80dd9a3c
[    4.251884] 5de0: 81c35e14 81c35df0 80616ec8 80616c60 00000001 810c45b0 81c35e6c 815c6810
[    4.260076] 5e00: 00000001 80dd9a3c 81c35e34 81c35e18 80617338 80616e90 00000000 81c35e6c
[    4.268269] 5e20: 80617284 81c34000 81c35e64 81c35e38 80614730 80617290 81c35e64 8171a06c
[    4.276461] 5e40: 81e220b8 7dbb550b 815c6810 81c34000 815c6854 81126e90 81c35e9c 81c35e68
[    4.284654] 5e60: 8061673c 806146a8 8060f5e0 815c6810 00000001 7dbb550b 00000000 810c5080
[    4.292847] 5e80: 810c5320 815c6810 81126e90 00000000 81c35eac 81c35ea0 80617554 80616650
[    4.301040] 5ea0: 81c35ecc 81c35eb0 80615694 80617544 810c5080 810c5080 810c5094 81126e90
[    4.309233] 5ec0: 81c35efc 81c35ed0 80615c6c 8061560c 80615bc0 810c50c0 817eeb00 81412800
[    4.317425] 5ee0: 814c3000 00000000 814c300d 81119a60 81c35f3c 81c35f00 80141488 80615bcc
[    4.325618] 5f00: 81c60000 81c34000 81c35f24 81c35f18 80143078 817eeb00 81412800 817eeb18
[    4.333811] 5f20: 81412818 81003d00 00000088 81412800 81c35f74 81c35f40 80141a48 80141298
[    4.342005] 5f40: 81c35f74 81c34000 801481ac 817efa40 817efc00 801417d8 817eeb00 00000000
[    4.350199] 5f60: 815a7e7c 81c34000 81c35fac 81c35f78 80149b1c 801417e4 817efc20 817efc20
[    4.358391] 5f80: ffffe000 817efa40 801499a8 00000000 00000000 00000000 00000000 00000000
[    4.366583] 5fa0: 00000000 81c35fb0 80100130 801499b4 00000000 00000000 00000000 00000000
[    4.374774] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    4.382966] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
[    4.391155] Backtrace:
[    4.393613] [<805eadcc>] (stdp2690_get_edid) from [<805eb138>] (ge_b850v3_lvds_get_modes+0x2c/0x5c)
[    4.402691]  r10:81c73840 r9:81c73894 r8:816d9800 r7:00001000 r6:824addc0 r5:81c73840
[    4.410534]  r4:810c35f0
[    4.413073] [<805eb10c>] (ge_b850v3_lvds_get_modes) from [<80594188>] (drm_helper_probe_single_connector_modes+0x1d4/0x84c)
[    4.424240]  r5:00000045 r4:810c35f0
[    4.427822] [<80593fb4>] (drm_helper_probe_single_connector_modes) from [<805d9694>] (drm_client_modeset_probe+0x200/0x1384)
[    4.439074]  r10:00000002 r9:00001000 r8:81e1ce40 r7:00001000 r6:826282c8 r5:826282c8
[    4.446917]  r4:00000008
[    4.449455] [<805d9494>] (drm_client_modeset_probe) from [<805a7f18>] (__drm_fb_helper_initial_config_and_unlock+0x54/0x5b4)
[    4.460713]  r10:0000000c r9:81c40908 r8:81e1ce40 r7:810c35f4 r6:00000010 r5:00000010
[    4.468556]  r4:81fbb700
[    4.471095] [<805a7ec4>] (__drm_fb_helper_initial_config_and_unlock) from [<805a8c78>] (drm_fbdev_client_hotplug+0x11c/0x1b0)
[    4.482434]  r10:0000000c r9:81c40908 r8:81e1ce40 r7:810c35f4 r6:00000010 r5:816d9800
[    4.490276]  r4:81fbb700
[    4.492814] [<805a8b5c>] (drm_fbdev_client_hotplug) from [<805a8dc4>] (drm_fbdev_generic_setup+0xb8/0x1a4)
[    4.502494]  r7:00000000 r6:00000010 r5:81fbb700 r4:816d9800
[    4.508160] [<805a8d0c>] (drm_fbdev_generic_setup) from [<805e47b0>] (imx_drm_bind+0xf0/0x130)
[    4.516805]  r7:810c42d0 r6:8179f810 r5:00000000 r4:816d9800
[    4.522474] [<805e46c0>] (imx_drm_bind) from [<8060db1c>] (try_to_bring_up_master+0x22c/0x2f0)
[    4.531116]  r7:81126b60 r6:81c40908 r5:81e1ea80 r4:824aa240
[    4.536783] [<8060d8f0>] (try_to_bring_up_master) from [<8060dc9c>] (__component_add+0xbc/0x184)
[    4.545597]  r10:815c6810 r9:80dd9a3c r8:80c4b95c r7:810c4d6c r6:00000000 r5:81e1ea80
[    4.553440]  r4:81fe9740
[    4.555980] [<8060dbe0>] (__component_add) from [<8060dd80>] (component_add+0x1c/0x20)
[    4.563921]  r7:eefd8e00 r6:815c6810 r5:815c6800 r4:8246b440
[    4.569589] [<8060dd64>] (component_add) from [<805e98a4>] (dw_hdmi_imx_probe+0xa8/0xe8)
[    4.577702] [<805e97fc>] (dw_hdmi_imx_probe) from [<80619574>] (platform_probe+0x6c/0xc8)
[    4.585908]  r9:80dd9a3c r8:81126e90 r7:81126e90 r6:810c45b0 r5:815c6810 r4:00000000
[    4.593662] [<80619508>] (platform_probe) from [<806168dc>] (really_probe+0xe8/0x460)
[    4.601524]  r7:81126e90 r6:810c45b0 r5:00000000 r4:815c6810
[    4.607191] [<806167f4>] (really_probe) from [<80616d04>] (__driver_probe_device+0xb0/0x230)
[    4.615658]  r7:815c6810 r6:81c35e6c r5:810c45b0 r4:815c6810
[    4.621326] [<80616c54>] (__driver_probe_device) from [<80616ec8>] (driver_probe_device+0x44/0xe0)
[    4.630313]  r9:80dd9a3c r8:00000003 r7:815c6810 r6:81c35e6c r5:8116e314 r4:8116e310
[    4.638068] [<80616e84>] (driver_probe_device) from [<80617338>] (__device_attach_driver+0xb4/0x12c)
[    4.647227]  r9:80dd9a3c r8:00000001 r7:815c6810 r6:81c35e6c r5:810c45b0 r4:00000001
[    4.654981] [<80617284>] (__device_attach_driver) from [<80614730>] (bus_for_each_drv+0x94/0xd8)
[    4.663794]  r7:81c34000 r6:80617284 r5:81c35e6c r4:00000000
[    4.669461] [<8061469c>] (bus_for_each_drv) from [<8061673c>] (__device_attach+0xf8/0x190)
[    4.677753]  r7:81126e90 r6:815c6854 r5:81c34000 r4:815c6810
[    4.683419] [<80616644>] (__device_attach) from [<80617554>] (device_initial_probe+0x1c/0x20)
[    4.691971]  r8:00000000 r7:81126e90 r6:815c6810 r5:810c5320 r4:810c5080
[    4.698681] [<80617538>] (device_initial_probe) from [<80615694>] (bus_probe_device+0x94/0x9c)
[    4.707318] [<80615600>] (bus_probe_device) from [<80615c6c>] (deferred_probe_work_func+0xac/0xf0)
[    4.716305]  r7:81126e90 r6:810c5094 r5:810c5080 r4:810c5080
[    4.721973] [<80615bc0>] (deferred_probe_work_func) from [<80141488>] (process_one_work+0x1fc/0x54c)
[    4.731139]  r10:81119a60 r9:814c300d r8:00000000 r7:814c3000 r6:81412800 r5:817eeb00
[    4.738981]  r4:810c50c0 r3:80615bc0
[    4.742563] [<8014128c>] (process_one_work) from [<80141a48>] (worker_thread+0x270/0x570)
[    4.750765]  r10:81412800 r9:00000088 r8:81003d00 r7:81412818 r6:817eeb18 r5:81412800
[    4.758608]  r4:817eeb00
[    4.761147] [<801417d8>] (worker_thread) from [<80149b1c>] (kthread+0x174/0x190)
[    4.768574]  r10:81c34000 r9:815a7e7c r8:00000000 r7:817eeb00 r6:801417d8 r5:817efc00
[    4.776417]  r4:817efa40
[    4.778955] [<801499a8>] (kthread) from [<80100130>] (ret_from_fork+0x14/0x24)
[    4.786201] Exception stack(0x81c35fb0 to 0x81c35ff8)
[    4.791266] 5fa0:                                     00000000 00000000 00000000 00000000
[    4.799459] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    4.807651] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[    4.814279]  r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:801499a8
[    4.822120]  r4:817efa40
[    4.824664] Code: e3a02080 e593001c e3a01d33 e3a05000 (e5979018)

Split the registration from the STDP4028 probe routine and only perform
registration once both the STDP4028 and STDP2690 have probed.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>
CC: Peter Senna Tschudin <peter.senna@gmail.com>
CC: Martyn Welch <martyn.welch@collabora.co.uk>
CC: Neil Armstrong <narmstrong@baylibre.com>
CC: Robert Foss <robert.foss@linaro.org>
CC: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
CC: Jonas Karlman <jonas@kwiboo.se>
CC: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/43552c3404e8fdf92d8bc5658fac24e9f03c2c57.1637836606.git.martyn.welch@collabora.com