X hangs due to 'render ring' issue after suspend/closed lid

I am running Jessie on a toshiba laptop with these specs

Hardware: i7 5500u
Graphics: Intel HD graphics 5500
Linux 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt20-1+deb8u4 (2016-02-29) x86_64 GNU/Linux

I had to turn of power saving options (the screen can still be blanked after a few minutes but hibernate etc is out of the question) because after waking up from s suspended session/hibernation, the keyboard and mouse are completely unresponsive. The screen is partly restored (some windows are semi-transparent for effect) and I cannot go to single-user mode via key presses either.

Posted this on debian-laptop a while ago https://lists.debian.org/debian-laptop/2016/01/msg00027.html but that does not appear to be a very active list. Besides, The one suggestion that was very kindly offered involved using the keyboard, so I'm still stuck.

The problem seems to be with the Intel graphics driver. I filed a bug report about what happens when I suspend - resume at bugzilla.org https://bugs.freedesktop.org/show_bug.cgi?id=93868 but not sure whether this bug is now considered solved, active or left to its own devices?

After a reboot there is nothing for me to do but hold down the power button for 3s. After that I check the old log file (Xorg.0.log.old) and this seems to be the offending section:

[drm] stuck on render ring
[drm] GPU HANG: ecode 0:0x00dff888, in Xorg [751], reason: Ring hung, action: reset
[drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
[drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI -> DRM/Intel
[drm] drm/i915 developers can then reassign to the right component if it's not a kernel issue.
[drm] The gpu crash dump is required to analyze gpu hangs, so please always attach it.
[drm] GPU crash dump saved to /sys/class/drm/card0/error
[drm] Enabling RC6 states: RC6 on, RC6p off, RC6pp off

The post to BugZilla also includes a -GZipped- file /sys/class/drm/card0/error from right after the fact whose first 13 lines are:

GPU HANG: ecode 0:0x00dff888, in Xorg [751], reason: Ring hung, action: reset
Time: 1453805023 s 872139 us
Kernel: 3.16.0-4-amd64
Active process (on ring render): Xorg [751]
Reset count: 0
Suspend count: 1
PCI ID: 0x1616
EIR: 0x00000000
IER: 0x00000000
PGTBL_ER: 0x00000000
FORCEWAKE: 0x00010001
DERRMR: 0x2070ef2f
CCID: 0x028f510d

... and the total no. of lines is 151,075. None of which make sense to me...

One solution offered in BugZilla (https://bugs.freedesktop.org/show_bug.cgi?id=91152) that lies within my linux knowledge I tried: adding the option
intel_iommu=igfx_off

to the boot parameters in grub.cfg.

Unfortunately that makes no difference in my case. If I close the lid and open it again after everything's gone quiet - nothing

Does anyone in this group know of a working and understandable-by-limited-time-enthusiast solution?

As said I have all the power-saving options off, but if the lid is closed it still continues to hang.

Many thanks, happy to send more details.