[Intel-gfx] [BUG] i915 RC6 lockup

[Ben Widawsky]

On Tue, 16 Oct 2012 15:19:26 +0200
Jonas Jelten <jelten at in.tum.de> wrote:

> Hi list!
> 
> I think i've got a problem with the intel driver:
> 
> Sometimes, I think especially after running graphics intense
> applications, RC6 is disabled completely and heats up my Thinkpad
> X220t to 90 degree celsius, while idling.
> 
> At first I thought that this is a CPU frequency scaling issue, as the
> cpufreq_powersave claims to be running at 800 MHz, but i7z
> (http://code.google.com/p/i7z/) shows all multipliers to be 25 -> 2.5
> GHz CPU clock.
> 
> Powertop 2.1 reveals that the GPU is 100% active, 0% RC6, 0% RC6p and
> 0% RC6pp, and the CPU is 99,9% in C7-deep-sleep, at maximum frequency.
> /sys/kernel/debug/dri/0/i915_ring_freq_table also pointed the issue to
> being caused by the GPU.

Do you mean the GPU is 0% active? If you really mean 100% then the
results are expected, though I'm not sure how powertop attempts to
calculate the GPU activity. I'm guessing it's just 100 - rc6
state percentage, which when rc6 works is probably pretty close to
reasonable.

> 
> intel_gpu_top shows a total idle.

This indicates the above assumption is true.

> 
> I'm on ArchLinux, Kernel 3.6.2, xf86-video-intel-git
> b42d81b63f5b6a571faffaadd42c74adce40128a, this is 2.20.10.
> Problem first occured with Kernel 3.6.0.
> Core i5-2520M HD 3000

Obviously a bisect of the exact failing commit would be fantastic.

> 
> >cat /proc/cmdline
> >cryptdevice=/dev/sda2:cryptroot root=/dev/mapper/cryptroot ro vga=791
> >i915.i915_enable_rc6=7 i915.modeset=1 i915.lvds_downclock=1
> >i915.semaphores=1 drm.vblankoffdelay=1 init=/bin/systemd
> >initrd=../initramfs-linux.img BOOT_IMAGE=../vmlinuz-linux

First and most obvious, do not set rc6=7. If you do, do not file
bug reports with those results. RC6++ is known to be extremely broken,
and why we let users so easily hurt themselves is probably something we
need to remedy. On HD3000, even rc6+ is highly recommended against.

> 
> Sometimes it can be fixed by going to pm-suspend and waking up. A
> reboot always fixes it, until it randomly locks up the GPU again.
> 
> Please help me how i can do further investigation to catch the bug.

If you can reproduce it with rc6=1, then it echoes some other bugs
we're trying to track down. Figuring out the most minimal test case to
make it occur would be helpful. Also you can search the mailing list
for RPS related patches which seem to be related. Trying some of those
and reporting your results would be helpful.

Double check your dmesg for any GPU hangs which may have occurred before
the laptop becomes a space heater.


> 
> As this makes my Laptop consume ~40W, it would be really nice if this
> gets fixed.
> 
> 
> Cheers,
> 
> Jonas
> 
>