[Intel-gfx] [PATCH] drm/i915: Do a lightweight pm_get() from intel_mark_busy()

[Chris Wilson]

On Wed, Jun 24, 2015 at 10:40:02AM +0200, Daniel Vetter wrote:
> On Wed, Jun 24, 2015 at 09:09:03AM +0100, Chris Wilson wrote:
> > Akash noticed that we were recursing from the call to
> > intel_runtime_pm_get() inside intel_mark_busy() when we were already
> > waking the device (through another intel_runtime_pm_get()). In
> > intel_mark_busy() we know the device is awake and purpose of the
> > reference here is to simply keep the device awake until the GPU is idle
> > again. As such we do not need the full resume, and can call the lighter
> > intel_runtime_pm_get_noresume() instead.
> 
> How does that happen? I only see a mark_busy in add_request, and we
> shouldn't call that from intel_rpm_get(). Or do we? Calltrace of how this
> happens would be great.

>From the vlv wa:

[<ffffffff81b2d426>] dump_stack+0x4e/0x7a
[<ffffffff8108c40d>] warn_slowpath_common+0x7d/0xa0
[<ffffffff8108c4ea>] warn_slowpath_null+0x1a/0x20
[<ffffffff815656e5>] intel_runtime_pm_get+0xc5/0xf0
[<ffffffff81583f2e>] __i915_add_request+0x5e/0x340
[<ffffffff815772a3>] i915_gem_context_enable+0x93/0xb0
[<ffffffff81586e19>] i915_gem_init_hw+0xd9/0x270
[<ffffffff81552585>] intel_runtime_resume+0x105/0x370
[<ffffffff8146e569>] ? pci_restore_state.part.36+0xc9/0x1f0
[<ffffffff8147103b>] pci_pm_runtime_resume+0x7b/0xc0
[<ffffffff81470fc0>] ? pci_restore_standard_config+0x60/0x60
[<ffffffff8162a7f2>] __rpm_callback+0x32/0x70
[<ffffffff8162a856>] rpm_callback+0x26/0xa0
[<ffffffff8162b0f6>] rpm_resume+0x496/0x6f0
[<ffffffff8162c33f>] __pm_runtime_resume+0x4f/0x90
[<ffffffff815656a6>] intel_runtime_pm_get+0x86/0xf0
[<ffffffff81565865>] intel_display_power_rpm_get+0x125/0x170
[<ffffffff815658c3>] intel_display_power_get+0x13/0x20
[<ffffffff815d66a7>] intel_connector_dpms+0x57/0x120
[<ffffffff815394e9>] drm_mode_obj_set_property_ioctl+0x399/0x3a0
[<ffffffff815281c9>] drm_ioctl+0x1e9/0x5a0
[<ffffffff81539150>] ? drm_mode_obj_get_properties_ioctl+0x140/0x140
[<ffffffff813ccb57>] ? inode_has_perm.isra.32+0x27/0x40
[<ffffffff813ccc86>] ? file_has_perm+0x86/0xa0
[<ffffffff815698d5>] i915_compat_ioctl+0x45/0x50
[<ffffffff8120cb30>] compat_sys_ioctl+0xc0/0x13e0
[<ffffffff811d517e>] ? __fget+0x6e/0xb0
[<ffffffff81436a8b>] ? trace_hardirqs_on_thunk+0x3a/0x3c
[<ffffffff81b3c189>] ia32_do_call+0x13/0x1
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre