Re: [PATCH v2 2/2] drm/i915: Prevent the system suspend complete optimization

[Lukas Wunner <lukas@wunner.de>]

On Mon, Apr 24, 2017 at 05:27:43PM +0300, Imre Deak wrote:
> Since
> 
> commit bac2a909a096c9110525c18cbb8ce73c660d5f71
> Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Date:   Wed Jan 21 02:17:42 2015 +0100
> 
>     PCI / PM: Avoid resuming PCI devices during system suspend

This is not the commit you are looking for. :-)  See below.


> PCI devices will default to allowing the system suspend complete
> optimization where devices are not woken up during system suspend if
> they were already runtime suspended. This however breaks the i915/HDA
> drivers for two reasons:
> 
> - The i915 driver has system suspend specific steps that it needs to
>   run, that bring the device to a different state than its runtime
>   suspended state.
> 
> - The HDA driver's suspend handler requires power that it will request
>   from the i915 driver's power domain handler. This in turn requires the
>   i915 driver to runtime resume itself, but this won't be possible if the
>   suspend complete optimization is in effect: in this case the i915
>   runtime PM is disabled and trying to get an RPM reference returns
>   -EACCESS.

Hm, sounds like something that needs to be solved with device_links.


> 
> Solve this by requiring the PCI/PM core to resume the device during
> system suspend which in effect disables the suspend complete optimization.
> 
> One possibility for this bug staying hidden for so long is that the
> optimization for a device is disabled if it's disabled for any of its
> children devices. i915 may have a backlight device as its child which
> doesn't support runtime PM and so doesn't allow the optimization either.
> So if this backlight device got registered the bug stayed hidden.

No, the reason this hasn't popped up earlier is because direct_complete
has only been enabled for DRM devices for a few months now, to be specific
since

    commit d14d2a8453d650bea32a1c5271af1458cd283a0f
    Author: Lukas Wunner <lukas@wunner.de>
    Date:   Wed Jun 8 12:49:29 2016 +0200

    drm: Remove dev_pm_ops from drm_class

which landed in v4.8.

(Sorry for not raising my voice earlier, this patch appeared on my radar
just now.)

Kind regards,

Lukas

> 
> Credits to Marta, Tomi and David who enabled pstore logging,
> that caught one instance of this issue across a suspend/
> resume-to-ram and Ville who rememberd that the optimization was enabled
> for some devices at one point.
> 
> The first WARN triggered by the problem:
> 
> [ 6250.746445] WARNING: CPU: 2 PID: 17384 at drivers/gpu/drm/i915/intel_runtime_pm.c:2846 intel_runtime_pm_get+0x6b/0xd0 [i915]
> [ 6250.746448] pm_runtime_get_sync() failed: -13
> [ 6250.746451] Modules linked in: snd_hda_intel i915 vgem snd_hda_codec_hdmi x86_pkg_temp_thermal intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul
> snd_hda_codec_realtek snd_hda_codec_generic ghash_clmulni_intel e1000e snd_hda_codec snd_hwdep snd_hda_core ptp mei_me pps_core snd_pcm lpc_ich mei prime_
> numbers i2c_hid i2c_designware_platform i2c_designware_core [last unloaded: i915]
> [ 6250.746512] CPU: 2 PID: 17384 Comm: kworker/u8:0 Tainted: G     U  W       4.11.0-rc5-CI-CI_DRM_334+ #1
> [ 6250.746515] Hardware name:                  /NUC5i5RYB, BIOS RYBDWi35.86A.0362.2017.0118.0940 01/18/2017
> [ 6250.746521] Workqueue: events_unbound async_run_entry_fn
> [ 6250.746525] Call Trace:
> [ 6250.746530]  dump_stack+0x67/0x92
> [ 6250.746536]  __warn+0xc6/0xe0
> [ 6250.746542]  ? pci_restore_standard_config+0x40/0x40
> [ 6250.746546]  warn_slowpath_fmt+0x46/0x50
> [ 6250.746553]  ? __pm_runtime_resume+0x56/0x80
> [ 6250.746584]  intel_runtime_pm_get+0x6b/0xd0 [i915]
> [ 6250.746610]  intel_display_power_get+0x1b/0x40 [i915]
> [ 6250.746646]  i915_audio_component_get_power+0x15/0x20 [i915]
> [ 6250.746654]  snd_hdac_display_power+0xc8/0x110 [snd_hda_core]
> [ 6250.746661]  azx_runtime_resume+0x218/0x280 [snd_hda_intel]
> [ 6250.746667]  pci_pm_runtime_resume+0x76/0xa0
> [ 6250.746672]  __rpm_callback+0xb4/0x1f0
> [ 6250.746677]  ? pci_restore_standard_config+0x40/0x40
> [ 6250.746682]  rpm_callback+0x1f/0x80
> [ 6250.746686]  ? pci_restore_standard_config+0x40/0x40
> [ 6250.746690]  rpm_resume+0x4ba/0x740
> [ 6250.746698]  __pm_runtime_resume+0x49/0x80
> [ 6250.746703]  pci_pm_suspend+0x57/0x140
> [ 6250.746709]  dpm_run_callback+0x6f/0x330
> [ 6250.746713]  ? pci_pm_freeze+0xe0/0xe0
> [ 6250.746718]  __device_suspend+0xf9/0x370
> [ 6250.746724]  ? dpm_watchdog_set+0x60/0x60
> [ 6250.746730]  async_suspend+0x1a/0x90
> [ 6250.746735]  async_run_entry_fn+0x34/0x160
> [ 6250.746741]  process_one_work+0x1f2/0x6d0
> [ 6250.746749]  worker_thread+0x49/0x4a0
> [ 6250.746755]  kthread+0x107/0x140
> [ 6250.746759]  ? process_one_work+0x6d0/0x6d0
> [ 6250.746763]  ? kthread_create_on_node+0x40/0x40
> [ 6250.746768]  ret_from_fork+0x2e/0x40
> [ 6250.746778] ---[ end trace 102a62fd2160f5e6 ]---
> 
> v2:
> - Use the new pci_dev->needs_resume flag, to avoid any overhead during
>   the ->pm_prepare hook. (Rafael)
> 
> Fixes: bac2a909a096 ("PCI / PM: Avoid resuming PCI devices during system suspend")
> References: https://bugs.freedesktop.org/show_bug.cgi?id=100378
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Marta Lofstedt <marta.lofstedt@intel.com>
> Cc: David Weinehall <david.weinehall@linux.intel.com>
> Cc: Tomi Sarvela <tomi.p.sarvela@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Takashi Iwai <tiwai@suse.de>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: linux-pci@vger.kernel.org
> Cc: stable@vger.kernel.org
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> (v1)
> ---
>  drivers/gpu/drm/i915/i915_drv.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 8be958f..dd7ce69 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1207,6 +1207,15 @@ int i915_driver_load(struct pci_dev *pdev, const struct pci_device_id *ent)
>  		goto out_free_priv;
>  
>  	pci_set_drvdata(pdev, &dev_priv->drm);
> +	/*
> +	 * Disable the system suspend direct complete optimization, which can
> +	 * leave the device suspended skipping the driver's suspend handlers
> +	 * if the device was already runtime suspended. This is needed due to
> +	 * the difference in our runtime and system suspend sequence and
> +	 * becaue the HDA driver may require us to enable the audio power
> +	 * domain during system suspend.
> +	 */
> +	pci_resume_before_suspend(pdev, true);
>  
>  	ret = i915_driver_init_early(dev_priv, ent);
>  	if (ret < 0)
> -- 
> 2.5.0
>