Below, dmesg logs with drm debug=1. 
First, switching to console and back with a sane system (a system that has not 
been suspended before, so the console are working).
Then with a broken system (has been suspended before).  

There is not logs differences when switching to console, but there's a slight
difference when switching back from to console to X11.

I added comments to show the different moments.

== this with a sane system (has not been suspended before) ==

# new dmesg logs when I switch from X11 to console (ctrl-alt-f1) :
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x40086414, nr=0x14, dev 0xe200, auth=1
[drm:drm_irq_uninstall] irq=17
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
# and here is what is loggued when I switch back from console to X11 :
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4018641b, nr=0x1b, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] ret = -22
[drm:drm_unlocked_ioctl] pid=5482, cmd=0xc0186415, nr=0x15, dev 0xe200, auth=1
[drm:drm_addmap_core] offset = 0xd0100000, size = 0x00500000, type = 3
[drm:drm_addmap_core] AGP offset = 0xd0100000, size = 0x00500000
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x40446440, nr=0x40, dev 0xe200, auth=1
[drm:i915_dma_resume] 
[drm:i915_dma_resume] hw status page @ f3b49000
[drm:i915_dma_resume] Enabled hardware status page
[drm:drm_unlocked_ioctl] pid=5482, cmd=0xc0106403, nr=0x03, dev 0xe200, auth=1
[drm:drm_irq_by_busid] 0:2:0 => IRQ 17
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x40086414, nr=0x14, dev 0xe200, auth=1
[drm:drm_irq_install] irq=17
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1

== this is with a broken-console system (has been suspended before) ==

# dmesg logs appearing when switching from xorg to console :
# identical (exactly same logs as with a sane/working system)
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x40086414, nr=0x14, dev 0xe200, auth=1
[drm:drm_irq_uninstall] irq=17
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
# then when I switch back from console to X11 :
# (now, there's differences, below, with a sane system)
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
#--> begin differing (from sane system) logs
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x40446440, nr=0x40, dev 0xe200, auth=1
#<-- end differing part
# the remaining is identical to a sane system
[drm:i915_dma_resume] 
[drm:i915_dma_resume] hw status page @ f3b49000
[drm:i915_dma_resume] Enabled hardware status page
[drm:drm_unlocked_ioctl] pid=5482, cmd=0xc0106403, nr=0x03, dev 0xe200, auth=1
[drm:drm_irq_by_busid] 0:2:0 => IRQ 17
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x40086414, nr=0x14, dev 0xe200, auth=1
[drm:drm_irq_install] irq=17
[drm:drm_unlocked_ioctl] pid=5482, cmd=0x4004644d, nr=0x4d, dev 0xe200, auth=1