Re: [PATCH 2/6] drm/i915/pm: Hoist pci_save_state()+pci_set_power_state() to the end of pm _late() hook

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Sep 26, 2024 at 06:41:17PM +0300, Ville Syrjälä wrote:
> On Thu, Sep 26, 2024 at 10:43:21AM -0400, Rodrigo Vivi wrote:
> > On Wed, Sep 25, 2024 at 05:45:22PM +0300, Ville Syrjala wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > driver/pci does the pci_save_state()+pci_set_power_state() from the
> > > _noirq() pm hooks. Move our manual calls (needed for the hibernate+D3
> > > workaround with buggy BIOSes) towards that same point. We currently
> > > have no _noirq() hooks, so end of _late() hooks is the best we can
> > > do right now.
> > > 
> > > Cc: Bjorn Helgaas <bhelgaas@google.com>
> > > Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> > > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > Cc: linux-pci@vger.kernel.org
> > > Cc: intel-gfx@lists.freedesktop.org
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_driver.c | 19 ++++++++++++++-----
> > >  1 file changed, 14 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
> > > index 6dc0104a3e36..9d557ff8adf5 100644
> > > --- a/drivers/gpu/drm/i915/i915_driver.c
> > > +++ b/drivers/gpu/drm/i915/i915_driver.c
> > > @@ -1015,7 +1015,6 @@ static int i915_drm_suspend(struct drm_device *dev)
> > >  {
> > >  	struct drm_i915_private *dev_priv = to_i915(dev);
> > >  	struct intel_display *display = &dev_priv->display;
> > > -	struct pci_dev *pdev = to_pci_dev(dev_priv->drm.dev);
> > >  	pci_power_t opregion_target_state;
> > >  
> > >  	disable_rpm_wakeref_asserts(&dev_priv->runtime_pm);
> > > @@ -1029,8 +1028,6 @@ static int i915_drm_suspend(struct drm_device *dev)
> > >  		intel_display_driver_disable_user_access(dev_priv);
> > >  	}
> > >  
> > > -	pci_save_state(pdev);
> > > -
> > >  	intel_display_driver_suspend(dev_priv);
> > >  
> > >  	intel_dp_mst_suspend(dev_priv);
> > > @@ -1090,10 +1087,16 @@ static int i915_drm_suspend_late(struct drm_device *dev, bool hibernation)
> > >  		drm_err(&dev_priv->drm, "Suspend complete failed: %d\n", ret);
> > >  		intel_power_domains_resume(dev_priv);
> > >  
> > > -		goto out;
> > > +		goto fail;
> > >  	}
> > >  
> > > +	enable_rpm_wakeref_asserts(rpm);
> > > +
> > > +	if (!dev_priv->uncore.user_forcewake_count)
> > > +		intel_runtime_pm_driver_release(rpm);
> > > +
> > 
> > why do we need this?
> > probably deserves a separate patch?
> 
> It was there already.

yes, but it was done in a later stage and now it is called earlier
in the regular path. I believe it deserves a 'why' that is not clear
in this commit message.

> 
> > 
> > >  	pci_disable_device(pdev);
> > > +
> > >  	/*
> > >  	 * During hibernation on some platforms the BIOS may try to access
> > >  	 * the device even though it's already in D3 and hang the machine. So
> > > @@ -1105,11 +1108,17 @@ static int i915_drm_suspend_late(struct drm_device *dev, bool hibernation)
> > >  	 * Lenovo Thinkpad X301, X61s, X60, T60, X41
> > >  	 * Fujitsu FSC S7110
> > >  	 * Acer Aspire 1830T
> > > +	 *
> > > +	 * pci_save_state() is needed to prevent driver/pci from
> > > +	 * automagically putting the device into D3.
> > >  	 */
> > 
> > I'm still not convinced that this would automagically prevent the D3,
> > specially in this part of the code.
> 
> You need to read pci_pm_poweroff_noirq()
> 
> > 
> > I would prefer to simply remove this call, or keep it and move it
> > here to be consistent with other drivers, but also add the restore
> > portion of it for consistency and alignment...
> > 
> > > +	pci_save_state(pdev);
> > >  	if (!(hibernation && GRAPHICS_VER(dev_priv) < 6))
> > >  		pci_set_power_state(pdev, PCI_D3hot);
> > >  
> > > -out:
> > > +	return 0;
> > > +
> > > +fail:
> > >  	enable_rpm_wakeref_asserts(rpm);
> > >  	if (!dev_priv->uncore.user_forcewake_count)
> > >  		intel_runtime_pm_driver_release(rpm);
> > > -- 
> > > 2.44.2
> > > 
> 
> -- 
> Ville Syrjälä
> Intel