Re: i915 DRMKMS GPU hang

[Iain Hibbert <plunky%ogmig.net@localhost>]

On Tue, 2 Feb 2016, John D. Baker wrote:

> the display freezes for a couple of minutes shortly after starting X
> following a reboot--usually a couple of minutes after logging in via
> 'xdm'.  I then see the following in 'dmesg' and XConsole.  It seems only
> to occur once.  If it happened more than once in a session, it's been
> too long ago for me to remember.
> 
> drm: stuck on render ring
> drm: GPU HANG: ecode 0:0x3c8160c1, 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 error in i915_reset: Failed to reset chip: -19
> 
> After this, it seems to operate normally essentially indefinitely.

I think after this, it is not any longer using the DRM (KMS?) magic code 
so it won't happen again.

I also see this GPU hang on a T60; from my dmesg

agp0 at pchb0: i915-family chipset
i915drmkms0 at pci0 dev 2 function 0: vendor 8086 product 27a2 (rev. 0x03)
drm: Memory usable by graphics device = 256M
drm: Supports vblank timestamp caching Rev 2 (21.10.2013).
drm: Driver supports precise vblank timestamp query.
i915drmkms0: interrupting at ioapic0 pin 16 (i915)
drm: initialized overlay support
intelfb0 at i915drmkms0
i915drmkms0: info: registered panic notifier
intelfb0: framebuffer at 0xdb1b9000, size 1400x1050, depth 32, stride 5632
wsdisplay0 at intelfb0 kbdmux 1: console (default, vt100 emulation), using wskbd0
wsmux1: connecting to wsdisplay0
vendor 8086 product 27a6 (miscellaneous display, revision 0x03) at pci0 dev 2 function 1 not configured

and then a very short time after or during boot, I usually see

DRM error in i915_irq_handler: pipe A underrun

though I have done nothing about this - I run with the intel_old driver 
instead, which works seemingly well enough.

iain