Re: [PATCH 1/2] vga_switcheroo: add power support for windows 10 machines.

[Lukas Wunner]

Hi Dave,

On Wed, Mar 09, 2016 at 04:14:04PM +1000, Dave Airlie wrote:
> From: Dave Airlie <airlied@xxxxxxxxxx>
> 
> Windows 10 seems to have standardised power control for the
> optimus/powerxpress laptops using PR3 power resource hooks.

What happened to the Optimus DSM, does this still work? If not,
echoing OFF to the vgaswitcheroo sysfs file won't power down the
GPU now, right? (If runtime pm is disabled in nouveau.)

> I'm not sure this is definitely the correct place to be
> doing this, but it works for me here.

How about implementing an additional vga_switcheroo handler somewhere
in drivers/acpi/, which looks for the PR3 hooks and registers with
vga_switcheroo if found. The ->power_state callback of that handler
would then invoke acpi_device_set_power().

The ACPI bus is scanned in the subsys_initcall section, much earlier
than nouveau is loaded (in the device_initcall section). So the ACPI
vga_switcheroo handler could register before the nouveau DSM handler
and therefore would always have a higher precedence.

In any case this patch should be amended with kerneldoc for
vga_switcheroo_init_parent_pr3_ops(), I've spent considerable time
last year to document everything and kindly ask that this water not
be muddied again. ;-)

One small nit, the headers are sorted alphabetically yet acpi.h is
added at the end.

Thanks,

Lukas

> 
> The ACPI device for the GPU I have is \_SB_.PCI0.PEG_.VID_
> but the power resource hooks are on \_SB_.PCI0.PEG_, so
> this patch creates a new power domain to turn the GPU
> device parent off using standard ACPI calls.
> 
> Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
> ---
>  drivers/gpu/vga/vga_switcheroo.c | 54 +++++++++++++++++++++++++++++++++++++++-
>  include/linux/vga_switcheroo.h   |  3 ++-
>  2 files changed, 55 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/vga/vga_switcheroo.c b/drivers/gpu/vga/vga_switcheroo.c
> index 665ab9f..be32cb2 100644
> --- a/drivers/gpu/vga/vga_switcheroo.c
> +++ b/drivers/gpu/vga/vga_switcheroo.c
> @@ -42,7 +42,7 @@
>  #include <linux/uaccess.h>
>  #include <linux/vgaarb.h>
>  #include <linux/vga_switcheroo.h>
> -
> +#include <linux/acpi.h>
>  /**
>   * DOC: Overview
>   *
> @@ -997,3 +997,55 @@ vga_switcheroo_init_domain_pm_optimus_hdmi_audio(struct device *dev,
>  	return -EINVAL;
>  }
>  EXPORT_SYMBOL(vga_switcheroo_init_domain_pm_optimus_hdmi_audio);
> +
> +/* With Windows 10 the runtime suspend/resume can use power
> +   resources on the parent device */
> +static int vga_acpi_switcheroo_runtime_suspend(struct device *dev)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	int ret;
> +	struct acpi_device *adev;
> +
> +	ret = dev->bus->pm->runtime_suspend(dev);
> +	if (ret)
> +		return ret;
> +
> +	ret = acpi_bus_get_device(ACPI_HANDLE(&pdev->dev), &adev);
> +	if (!ret)
> +		acpi_device_set_power(adev->parent, ACPI_STATE_D3_COLD);
> +	return 0;
> +}
> +
> +static int vga_acpi_switcheroo_runtime_resume(struct device *dev)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	struct acpi_device *adev;
> +	int ret;
> +
> +	ret = acpi_bus_get_device(ACPI_HANDLE(&pdev->dev), &adev);
> +	if (!ret)
> +		acpi_device_set_power(adev->parent, ACPI_STATE_D0);
> +	ret = dev->bus->pm->runtime_resume(dev);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +int vga_switcheroo_init_parent_pr3_ops(struct device *dev,
> +				       struct dev_pm_domain *domain)
> +
> +{
> +	/* copy over all the bus versions */
> +	if (dev->bus && dev->bus->pm) {
> +		domain->ops = *dev->bus->pm;
> +		domain->ops.runtime_suspend = vga_acpi_switcheroo_runtime_suspend;
> +		domain->ops.runtime_resume = vga_acpi_switcheroo_runtime_resume;
> +
> +		dev_pm_domain_set(dev, domain);
> +		return 0;
> +	}
> +	dev_pm_domain_set(dev, NULL);
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL(vga_switcheroo_init_parent_pr3_ops);
> diff --git a/include/linux/vga_switcheroo.h b/include/linux/vga_switcheroo.h
> index 69e1d4a1..5ce0cbe 100644
> --- a/include/linux/vga_switcheroo.h
> +++ b/include/linux/vga_switcheroo.h
> @@ -144,6 +144,7 @@ void vga_switcheroo_set_dynamic_switch(struct pci_dev *pdev, enum vga_switcheroo
>  int vga_switcheroo_init_domain_pm_ops(struct device *dev, struct dev_pm_domain *domain);
>  void vga_switcheroo_fini_domain_pm_ops(struct device *dev);
>  int vga_switcheroo_init_domain_pm_optimus_hdmi_audio(struct device *dev, struct dev_pm_domain *domain);
> +int vga_switcheroo_init_parent_pr3_ops(struct device *dev, struct dev_pm_domain *domain);
>  #else
>  
>  static inline void vga_switcheroo_unregister_client(struct pci_dev *dev) {}
> @@ -163,6 +164,6 @@ static inline void vga_switcheroo_set_dynamic_switch(struct pci_dev *pdev, enum
>  static inline int vga_switcheroo_init_domain_pm_ops(struct device *dev, struct dev_pm_domain *domain) { return -EINVAL; }
>  static inline void vga_switcheroo_fini_domain_pm_ops(struct device *dev) {}
>  static inline int vga_switcheroo_init_domain_pm_optimus_hdmi_audio(struct device *dev, struct dev_pm_domain *domain) { return -EINVAL; }
> -
> +static inline int vga_switcheroo_init_parent_pr3_ops(struct device *dev, struct dev_pm_domain *domain) { return -EINVAL; }
>  #endif
>  #endif /* _LINUX_VGA_SWITCHEROO_H_ */
> -- 
> 2.5.0