Re: [PATCH v2] drm/i915: Invoke BXT _DSM to enable MUX on HP Workstation laptops

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 23 Apr 2021, Kai-Heng Feng <kai.heng.feng@canonical.com> wrote:
> On HP Fury G7 Workstations, graphics output is re-routed from Intel GFX
> to discrete GFX after S3. This is not desirable, because userspace will
> treat connected display as a new one, losing display settings.
>
> The expected behavior is to let discrete GFX drives all external
> displays.
>
> The platform in question uses ACPI method \_SB.PCI0.HGME to enable MUX.
> The method is inside the BXT _DSM, so add the _DSM and call it
> accordingly.
>
> I also tested some MUX-less and iGPU only laptops with the BXT _DSM, no
> regression was found.

I don't know whether this change is the right thing to do. I don't know
if it isn't either. Need to look into it.

However, I have some general comments, inline.

>
> v2:
>  - Forward declare struct pci_dev.
>
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3113
> References: https://lore.kernel.org/intel-gfx/1460040732-31417-4-git-send-email-animesh.manna@intel.com/
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
>  drivers/gpu/drm/i915/display/intel_acpi.c | 17 +++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_acpi.h |  3 +++
>  drivers/gpu/drm/i915/i915_drv.c           |  5 +++++
>  3 files changed, 25 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
> index 833d0c1be4f1..c7b57c22dce3 100644
> --- a/drivers/gpu/drm/i915/display/intel_acpi.c
> +++ b/drivers/gpu/drm/i915/display/intel_acpi.c
> @@ -14,11 +14,16 @@
>  
>  #define INTEL_DSM_REVISION_ID 1 /* For Calpella anyway... */
>  #define INTEL_DSM_FN_PLATFORM_MUX_INFO 1 /* No args */
> +#define INTEL_DSM_FN_PLATFORM_BXT_MUX_INFO 0 /* No args */
>  
>  static const guid_t intel_dsm_guid =
>  	GUID_INIT(0x7ed873d3, 0xc2d0, 0x4e4f,
>  		  0xa8, 0x54, 0x0f, 0x13, 0x17, 0xb0, 0x1c, 0x2c);
>  
> +static const guid_t intel_bxt_dsm_guid =
> +	GUID_INIT(0x3e5b41c6, 0xeb1d, 0x4260,
> +		  0x9d, 0x15, 0xc7, 0x1f, 0xba, 0xda, 0xe4, 0x14);
> +
>  static char *intel_dsm_port_name(u8 id)
>  {
>  	switch (id) {
> @@ -176,6 +181,18 @@ void intel_unregister_dsm_handler(void)
>  {
>  }
>  
> +void intel_bxt_dsm_detect(struct pci_dev *pdev)

Please leave out bxt from the naming and make the argument struct
drm_i915_private *i915. Mmh, then it conflicts with existing
intel_dsm_detect(), maybe we need a more descriptive name altogether?

> +{
> +	acpi_handle dhandle;
> +
> +	dhandle = ACPI_HANDLE(&pdev->dev);
> +	if (!dhandle)
> +		return;
> +
> +	acpi_evaluate_dsm(dhandle, &intel_bxt_dsm_guid, INTEL_DSM_REVISION_ID,
> +			  INTEL_DSM_FN_PLATFORM_BXT_MUX_INFO, NULL);
> +}
> +
>  /*
>   * ACPI Specification, Revision 5.0, Appendix B.3.2 _DOD (Enumerate All Devices
>   * Attached to the Display Adapter).
> diff --git a/drivers/gpu/drm/i915/display/intel_acpi.h b/drivers/gpu/drm/i915/display/intel_acpi.h
> index e8b068661d22..d2d560d63bb3 100644
> --- a/drivers/gpu/drm/i915/display/intel_acpi.h
> +++ b/drivers/gpu/drm/i915/display/intel_acpi.h
> @@ -6,15 +6,18 @@
>  #ifndef __INTEL_ACPI_H__
>  #define __INTEL_ACPI_H__
>  
> +struct pci_dev;
>  struct drm_i915_private;
>  
>  #ifdef CONFIG_ACPI
>  void intel_register_dsm_handler(void);
>  void intel_unregister_dsm_handler(void);
> +void intel_bxt_dsm_detect(struct pci_dev *pdev);
>  void intel_acpi_device_id_update(struct drm_i915_private *i915);
>  #else
>  static inline void intel_register_dsm_handler(void) { return; }
>  static inline void intel_unregister_dsm_handler(void) { return; }
> +static inline void intel_bxt_dsm_detect(struct pci_dev *pdev) { return; }
>  static inline
>  void intel_acpi_device_id_update(struct drm_i915_private *i915) { return; }
>  #endif /* CONFIG_ACPI */
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 785dcf20c77b..57b12068aab4 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -853,6 +853,8 @@ int i915_driver_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  	if (ret)
>  		goto out_cleanup_gem;
>  
> +	intel_bxt_dsm_detect(pdev);
> +

The call sites in i915_driver_probe() and i915_drm_resume() seem rather
arbitrary.

Long term, I'd like most or all of the display stuff like this placed in
appropriate intel_modeset_*() functions in display/intel_display.c. I'm
not keen on having new and very specific calls in the higher levels.

At probe, feels like the routing should happen earlier, before output
setup? In intel_modeset_init_nogem()?

>  	i915_driver_register(i915);
>  
>  	enable_rpm_wakeref_asserts(&i915->runtime_pm);
> @@ -1215,6 +1217,7 @@ int i915_suspend_switcheroo(struct drm_i915_private *i915, pm_message_t state)
>  static int i915_drm_resume(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(dev);
> +	struct pci_dev *pdev = to_pci_dev(dev_priv->drm.dev);
>  	int ret;
>  
>  	disable_rpm_wakeref_asserts(&dev_priv->runtime_pm);
> @@ -1271,6 +1274,8 @@ static int i915_drm_resume(struct drm_device *dev)
>  
>  	intel_gvt_resume(dev_priv);
>  
> +	intel_bxt_dsm_detect(pdev);
> +

In intel_display_resume() perhaps?

(Yay for confusing naming wrt display and modeset, it's a
work-in-progress.)

BR,
Jani.


>  	enable_rpm_wakeref_asserts(&dev_priv->runtime_pm);
>  
>  	return 0;

-- 
Jani Nikula, Intel Open Source Graphics Center