Ok.  Performing a "jounalctl -xb" reveals the following for the hdmi probe.


[root@myodroid exynos]# journalctl -xb
-- Logs begin at Thu 2016-02-11 11:28:00 EST, end at Sat 2016-08-13 22:01:01 EDT. --
Feb 11 11:28:02 myodroid systemd-journald[180]: Runtime journal (/run/log/journal/) is 8.0M, max 98.9M, 90.9M free.
-- Subject: Disk space used by the journal
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Runtime journal (/run/log/journal/) is currently using 8.0M.
-- Maximum allowed usage is set to 98.9M.
-- Leaving at least 148.3M free (of currently available 981.0M of disk space).
-- Enforced usage limit is thus 98.9M, of which 90.9M are still available.
--
-- The limits controlling how much disk space is used by the journal may
-- be configured with SystemMaxUse=, SystemKeepFree=, SystemMaxFileSize=,
-- RuntimeMaxUse=, RuntimeKeepFree=, RuntimeMaxFileSize= settings in
-- /etc/systemd/journald.conf. See journald.conf(5) for details.
Feb 11 11:28:02 myodroid kernel: Booting Linux on physical CPU 0x100
Feb 11 11:28:02 myodroid kernel: Linux version 4.6.5-300.fc24.armv7hl (mockbuild@arm04-builder03.arm.fedoraproject.org) (gcc version 6.1.1 20160621 (Red Hat
Feb 11 11:28:02 myodroid kernel: CPU: ARMv7 Processor [410fc073] revision 3 (ARMv7), cr=10c5387d
Feb 11 11:28:02 myodroid kernel: CPU: div instructions available: patching division code
Feb 11 11:28:02 myodroid kernel: CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
Feb 11 11:28:02 myodroid kernel: Machine model: Hardkernel Odroid XU4
Feb 11 11:28:02 myodroid kernel: efi: Getting EFI parameters from FDT:
Feb 11 11:28:02 myodroid kernel: efi: UEFI not found.
Feb 11 11:28:02 myodroid kernel: cma: Reserved 64 MiB at 0xba800000
Feb 11 11:28:02 myodroid kernel: Memory policy: Data cache writealloc
Feb 11 11:28:02 myodroid kernel: Samsung CPU ID: 0xe5422001
Feb 11 11:28:02 myodroid kernel: On node 0 totalpages: 514560
Feb 11 11:28:02 myodroid kernel: free_area_init_node: node 0, pgdat c0edc900, node_mem_map eee24000
Feb 11 11:28:02 myodroid kernel:   Normal zone: 1728 pages used for memmap
Feb 11 11:28:02 myodroid kernel:   Normal zone: 0 pages reserved
Feb 11 11:28:02 myodroid kernel:   Normal zone: 192512 pages, LIFO batch:31
Feb 11 11:28:02 myodroid kernel:   HighMem zone: 322048 pages, LIFO batch:31
Feb 11 11:28:02 myodroid kernel: Running under secure firmware.
Feb 11 11:28:02 myodroid kernel: percpu: Embedded 13 pages/cpu @eed8a000 s24332 r8192 d20724 u53248
Feb 11 11:28:02 myodroid kernel: pcpu-alloc: s24332 r8192 d20724 u53248 alloc=13*4096
Feb 11 11:28:02 myodroid kernel: pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3 [0] 4 [0] 5 [0] 6 [0] 7
Feb 11 11:28:02 myodroid kernel: Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 512832
Feb 11 11:28:02 myodroid kernel: Kernel command line: ro root=UUID=4d70d307-a61d-4cda-9535-8a8849c262c2 cma=64M LANG=en_US.UTF-8
Feb 11 11:28:02 myodroid kernel: PID hash table entries: 4096 (order: 2, 16384 bytes)
...skipping...
Feb 11 11:28:11 myodroid kernel: [drm:hdmi_probe [exynosdrm]] *ERROR* failed to get regulators
Feb 11 11:28:11 myodroid kernel: [drm:hdmi_probe [exynosdrm]] *ERROR* hdmi_resources_init failed
Feb 11 11:28:11 myodroid kernel: exynos-hdmi 14530000.hdmi: Failed to get supply 'vdd': -517
Feb 11 11:28:11 myodroid kernel: [drm:hdmi_probe [exynosdrm]] *ERROR* failed to get regulators
Feb 11 11:28:11 myodroid kernel: [drm:hdmi_probe [exynosdrm]] *ERROR* hdmi_resources_init failed
Feb 11 11:28:11 myodroid kernel: exynos-rot 11c00000.rotator: The exynos rotator is probed successfully
Feb 11 11:28:11 myodroid kernel: exynos-drm-gsc 13e00000.video-scaler: failed to get system register.
Feb 11 11:28:11 myodroid kernel: exynos-drm-gsc 13e00000.video-scaler: drm gsc registered successfully.
Feb 11 11:28:11 myodroid kernel: exynos-drm-gsc 13e10000.video-scaler: failed to get system register.
Feb 11 11:28:11 myodroid kernel: exynos-drm-gsc 13e10000.video-scaler: drm gsc registered successfully.
Feb 11 11:28:11 myodroid kernel: exynos-drm-ipp exynos-drm-ipp: drm ipp registered successfully.
Feb 11 11:28:11 myodroid kernel: exynos-hdmi 14530000.hdmi: Failed to get supply 'vdd': -517
Feb 11 11:28:11 myodroid kernel: [drm:hdmi_probe [exynosdrm]] *ERROR* failed to get regulators
Feb 11 11:28:11 myodroid kernel: [drm:hdmi_probe [exynosdrm]] *ERROR* hdmi_resources_init failed
Feb 11 11:28:11 myodroid kernel: s5m-rtc s2mps14-rtc: rtc core: registered s5m-rtc as rtc0
Feb 11 11:28:11 myodroid kernel: exynos-hdmi 14530000.hdmi: Failed to get supply 'vdd': -517
Feb 11 11:28:11 myodroid kernel: [drm:hdmi_probe [exynosdrm]] *ERROR* failed to get regulators
Feb 11 11:28:11 myodroid kernel: [drm:hdmi_probe [exynosdrm]] *ERROR* hdmi_resources_init failed
Feb 11 11:28:11 myodroid kernel: vdd_ldo9: ramp_delay not set
Feb 11 11:28:11 myodroid kernel: vdd_ldo13: ramp_delay not set
Feb 11 11:28:11 myodroid kernel: vdd_ldo15: ramp_delay not set
Feb 11 11:28:11 myodroid kernel: vdd_sd: ramp_delay not set
Feb 11 11:28:11 myodroid kernel: [drm] Exynos DRM: using 14450000.mixer device for DMA mapping operations
Feb 11 11:28:11 myodroid kernel: exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops [exynosdrm])
Feb 11 11:28:11 myodroid kernel: exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops [exynosdrm])
Feb 11 11:28:11 myodroid kernel: exynos-drm exynos-drm: bound exynos-drm-vidi (ops vidi_component_ops [exynosdrm])
Feb 11 11:28:11 myodroid kernel: [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
Feb 11 11:28:11 myodroid kernel: [drm] No driver support for vblank timestamp query.
Feb