Re: [PATCH v3] drm/i915: Invoke another _DSM to enable MUX on HP Workstation laptops

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Apr 26, 2021 at 11:24:10PM +0800, Kai-Heng Feng 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 another _DSM, so add the _DSM and call it
> accordingly.
> 
> I also tested some MUX-less and iGPU only laptops with that _DSM, no
> regression was found.
> 
> v3:
>  - Remove BXT from names.
>  - Change the parameter type.
>  - Fold the function into intel_modeset_init_hw().
> 
> 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    | 18 ++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_acpi.h    |  3 +++
>  drivers/gpu/drm/i915/display/intel_display.c |  2 ++
>  3 files changed, 23 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
> index 833d0c1be4f1..d008d3976261 100644
> --- a/drivers/gpu/drm/i915/display/intel_acpi.c
> +++ b/drivers/gpu/drm/i915/display/intel_acpi.c
> @@ -13,12 +13,17 @@
>  #include "intel_display_types.h"
>  
>  #define INTEL_DSM_REVISION_ID 1 /* For Calpella anyway... */
> +#define INTEL_DSM_FN_PLATFORM_MUX_ENABLE 0 /* No args */

This block of defines is for the other DSM. We don't want to
mix these up. We also want to name it according to the spec,
so something like GET_BIOS_DATA_FUNCS_SUPPORTED. Similarly
for the intel_dsm_enable_mux() wrapper function. + it needs
a comment to document that some BIOSes abuse it to do MUX
initialization and whatnot.

We should perhaps rename all the old DSM stuff to
something a bit less generic as well...

>  #define INTEL_DSM_FN_PLATFORM_MUX_INFO 1 /* 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_dsm_guid2 =
> +	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 +181,19 @@ void intel_unregister_dsm_handler(void)
>  {
>  }
>  
> +void intel_dsm_enable_mux(struct drm_i915_private *i915)
> +{
> +	struct pci_dev *pdev = i915->drm.pdev;
> +	acpi_handle dhandle;
> +
> +	dhandle = ACPI_HANDLE(&pdev->dev);
> +	if (!dhandle)
> +		return;
> +
> +	acpi_evaluate_dsm(dhandle, &intel_dsm_guid2, INTEL_DSM_REVISION_ID,
> +			  INTEL_DSM_FN_PLATFORM_MUX_ENABLE, 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..def013cf6308 100644
> --- a/drivers/gpu/drm/i915/display/intel_acpi.h
> +++ b/drivers/gpu/drm/i915/display/intel_acpi.h
> @@ -11,11 +11,14 @@ struct drm_i915_private;
>  #ifdef CONFIG_ACPI
>  void intel_register_dsm_handler(void);
>  void intel_unregister_dsm_handler(void);
> +void intel_dsm_enable_mux(struct drm_i915_private *i915);
>  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_dsm_enable_mux(struct drm_i915_private *i915) { 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/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index a10e26380ef3..d79dae370b20 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -11472,6 +11472,8 @@ void intel_modeset_init_hw(struct drm_i915_private *i915)
>  {
>  	struct intel_cdclk_state *cdclk_state;
>  
> +	intel_dsm_enable_mux(i915);
> +

This should probably be somewhere around where we do all the other
semi ACPI related init (OpRegion/etc.).

>  	if (!HAS_DISPLAY(i915))
>  		return;
>  
> -- 
> 2.30.2

-- 
Ville Syrjälä
Intel