Re: [PATCH 6/6] drm/i915/pm: Use pci_dev->skip_bus_pm for hibernate vs. D3 workaround

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Sep 25, 2024 at 05:45:26PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> On some older laptops we have to leave the device in D0
> during hibernation, or else the BIOS just hangs and never
> finishes the hibernation.
> 
> Currently we are achieving that by skipping the
> pci_set_power_state(D3). However we also need to call
> pci_save_state() ahead of time, or else
> pci_pm_suspend_noirq() will do the pci_set_power_state(D3)
> anyway.
> 
> This is all rather ugly, and might cause us to deviate from
> standard pci pm behaviour in unknown ways since we always
> call pci_save_state() for any kind of suspend operation.
> 
> Stop calling pci_save_state()+pci_set_power_state() entirely
> (apart from the switcheroo paths) and instead set
> pci_dev->skip_bus_pm=true to prevent the D3 during hibernation
> on old machines. Apart from that we'll just let the normal
> pci pm code take care of everything for us.
> 
> 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 | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
> index c3e7225ea1ba..05948d00a874 100644
> --- a/drivers/gpu/drm/i915/i915_driver.c
> +++ b/drivers/gpu/drm/i915/i915_driver.c
> @@ -1123,13 +1123,9 @@ static int i915_drm_suspend_noirq(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.
>  	 */
> -	pci_save_state(pdev);
> -	if (!(hibernation && GRAPHICS_VER(dev_priv) < 6))
> -		pci_set_power_state(pdev, PCI_D3hot);
> +	if (hibernation && GRAPHICS_VER(dev_priv) < 6)
> +		pdev->skip_bus_pm = true;

.skip_bus_pm was previously strictly internal to
drivers/pci/pci-driver.c.  Not sure about using it outside
drivers/pci/; would want Rafael to chime in.

>  	return 0;
>  }
> @@ -1137,6 +1133,7 @@ static int i915_drm_suspend_noirq(struct drm_device *dev, bool hibernation)
>  int i915_driver_suspend_switcheroo(struct drm_i915_private *i915,
>  				   pm_message_t state)
>  {
> +	struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
>  	int error;
>  
>  	if (drm_WARN_ON_ONCE(&i915->drm, state.event != PM_EVENT_SUSPEND &&
> @@ -1158,6 +1155,9 @@ int i915_driver_suspend_switcheroo(struct drm_i915_private *i915,
>  	if (error)
>  		return error;
>  
> +	pci_save_state(pdev);
> +	pci_set_power_state(pdev, PCI_D3hot);
> +
>  	return 0;
>  }
>  
> -- 
> 2.44.2
>