[Intel-gfx] [PATCH] drm/i915/skl: enable PC9/10 power states during suspend-to-idle

Thu Nov 19 05:34:48 PST 2015

On Wed, Nov 18, 2015 at 06:44:43PM +0200, Imre Deak wrote:
> On ke, 2015-11-18 at 17:33 +0100, Daniel Vetter wrote:
> > On Wed, Nov 18, 2015 at 05:32:30PM +0200, Imre Deak wrote:
> > > During suspend-to-idle we need to keep the DMC firmware active and DC6
> > > enabled, since otherwise we won't reach deep system power states like
> > > PC9/10. The lead for this came from Nivedita who noticed that the
> > > kernel's turbostat tool didn't report any PC9/10 residency change
> > > across an 'echo freeze > /sys/power/state'.
> > > 
> > > Reported-by: Nivedita Swaminathan <nivedita.swaminathan at intel.com>
> > > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.c | 44 +++++++++++++++++++++++++++++++----------
> > >  drivers/gpu/drm/i915/i915_drv.h |  1 +
> > >  2 files changed, 35 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > > index 6344dfb..649e20a 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.c
> > > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > > @@ -624,6 +624,14 @@ static int vlv_resume_prepare(struct drm_i915_private *dev_priv,
> > >  			      bool rpm_resume);
> > >  static int bxt_resume_prepare(struct drm_i915_private *dev_priv);
> > >  
> > > +static bool suspend_to_idle(struct drm_i915_private *dev_priv)
> > > +{
> > > +#if IS_ENABLED(CONFIG_ACPI_SLEEP)
> > > +	if (acpi_target_system_state() < ACPI_STATE_S3)
> > > +		return true;
> > > +#endif
> > > +	return false;
> > > +}
> > >  
> > >  static int i915_drm_suspend(struct drm_device *dev)
> > >  {
> > > @@ -676,11 +684,7 @@ static int i915_drm_suspend(struct drm_device *dev)
> > >  
> > >  	i915_save_state(dev);
> > >  
> > > -	opregion_target_state = PCI_D3cold;
> > > -#if IS_ENABLED(CONFIG_ACPI_SLEEP)
> > > -	if (acpi_target_system_state() < ACPI_STATE_S3)
> > > -		opregion_target_state = PCI_D1;
> > > -#endif
> > > +	opregion_target_state = suspend_to_idle(dev_priv) ? PCI_D1 : PCI_D3cold;
> > >  	intel_opregion_notify_adapter(dev, opregion_target_state);
> > >  
> > >  	intel_uncore_forcewake_reset(dev, false);
> > > @@ -701,15 +705,26 @@ static int i915_drm_suspend(struct drm_device *dev)
> > >  static int i915_drm_suspend_late(struct drm_device *drm_dev, bool hibernation)
> > >  {
> > >  	struct drm_i915_private *dev_priv = drm_dev->dev_private;
> > > +	bool fw_csr;
> > >  	int ret;
> > >  
> > > -	intel_power_domains_suspend(dev_priv);
> > > +	fw_csr = suspend_to_idle(dev_priv) && dev_priv->csr.dmc_payload;
> > > +	/*
> > > +	 * In case of firmware assisted context save/restore don't manually
> > > +	 * deinit the power domains. This also means the CSR/DMC firmware will
> > > +	 * stay active, it will power down any HW resources as required and
> > > +	 * also enable deeper system power states that would be blocked if the
> > > +	 * firmware was inactive.
> > > +	 */
> > > +	if (!fw_csr)
> > > +		intel_power_domains_suspend(dev_priv);
> > >  
> > >  	ret = intel_suspend_complete(dev_priv);
> > >  
> > >  	if (ret) {
> > >  		DRM_ERROR("Suspend complete failed: %d\n", ret);
> > > -		intel_power_domains_init_hw(dev_priv, true);
> > > +		if (!fw_csr)
> > > +			intel_power_domains_init_hw(dev_priv, true);
> > >  
> > >  		return ret;
> > >  	}
> > > @@ -730,6 +745,8 @@ static int i915_drm_suspend_late(struct drm_device *drm_dev, bool hibernation)
> > >  	if (!(hibernation && INTEL_INFO(dev_priv)->gen < 6))
> > >  		pci_set_power_state(drm_dev->pdev, PCI_D3hot);
> > >  
> > > +	dev_priv->suspended_to_idle = suspend_to_idle(dev_priv);
> > > +
> > >  	return 0;
> > >  }
> > >  
> > > @@ -842,8 +859,10 @@ static int i915_drm_resume_early(struct drm_device *dev)
> > >  	 * FIXME: This should be solved with a special hdmi sink device or
> > >  	 * similar so that power domains can be employed.
> > >  	 */
> > > -	if (pci_enable_device(dev->pdev))
> > > -		return -EIO;
> > > +	if (pci_enable_device(dev->pdev)) {
> > > +		ret = -EIO;
> > > +		goto out;
> > > +	}
> > >  
> > >  	pci_set_master(dev->pdev);
> > >  
> > > @@ -861,7 +880,12 @@ static int i915_drm_resume_early(struct drm_device *dev)
> > >  		hsw_disable_pc8(dev_priv);
> > >  
> > >  	intel_uncore_sanitize(dev);
> > > -	intel_power_domains_init_hw(dev_priv, true);
> > > +
> > > +	if (!(dev_priv->suspended_to_idle && dev_priv->csr.dmc_payload))
> > > +		intel_power_domains_init_hw(dev_priv, true);
> > 
> > This doesn't work when e.g. system suspend to S3 fails, in which case dmc
> > will also survive. We need the pm core to tell us what really happened,
> > and Rafael Wyzocki was working on patches for that:
> > 
> > http://lkml.iu.edu/hypermail/linux/kernel/1510.0/04266.html
> > 
> > Specifically we need the pm_suspend/resume_via_firmware helpers.
> > Unfortunately these didn't make it into 4.4, so we need to pick Rafael.
> 
> I think it does work. We deactivate the firmware during S3,S4 suspend
> in any case and reprogram it during S3,S4 resume, so it doesn't matter
> if the firmware contents survive or not. What we want is to ensure that
> during suspend-to-idle we don't deactivate the firmware that is we
> don't disable DC6 and we can decide that based
> on acpi_target_system_state().

If S3 fails we would reprogram the DMC even though there is no need for it. Do
we know if that is allowed? Potentially the DMC could be doing something when we
reprogram it and put us in an undefined state. On the other hand, one would hope
that it's clever enough to put us back in a valid state when starting again.

I haven't seen any problems when reprogramming the DMC so I think this fix is ok
for now and we can do the proper fix when Rafael's patches land.

-Patrik

> 
> --Imre
> 
> > Cheers, Daniel
> > 
> > > +
> > > +out:
> > > +	dev_priv->suspended_to_idle = false;
> > >  
> > >  	return ret;
> > >  }
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > > index a32571f..4a50382 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > @@ -1882,6 +1882,7 @@ struct drm_i915_private {
> > >  	u32 chv_phy_control;
> > >  
> > >  	u32 suspend_count;
> > > +	bool suspended_to_idle;
> > >  	struct i915_suspend_saved_registers regfile;
> > >  	struct vlv_s0ix_state vlv_s0ix_state;
> > >  
> > > -- 
> > > 2.5.0
> > > 
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx at lists.freedesktop.org
> > > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > 
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