linux-kernel - Re: [PATCH] drm/i915: Switch TGL-H DP-IN to dGFX when it's supported

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Date:   Tue, 16 Aug 2022 19:29:11 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
        tvrtko.ursulin@...ux.intel.com, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Lyude Paul <lyude@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915: Switch TGL-H DP-IN to dGFX when it's supported

On Tue, Aug 16, 2022 at 4:06 PM Jani Nikula <jani.nikula@...ux.intel.com> wrote:
>
> On Tue, 16 Aug 2022, Kai-Heng Feng <kai.heng.feng@...onical.com> wrote:
> > On mobile workstations like HP ZBook Fury G8, iGFX's DP-IN can switch to
> > dGFX so external monitors are routed to dGFX, and more monitors can be
> > supported as result.
> >
> > To switch the DP-IN to dGFX, the driver needs to invoke _DSM function 20
> > on intel_dsm_guid2. This method is described in Intel document 632107.
>
> Is this the policy decision that we want to unconditionally make,
> though?

I believes so, so more external monitors can be supported at the same time.

Kai-Heng

>
> BR,
> Jani.
>
> >
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_acpi.c | 18 +++++++++++++++++-
> >  1 file changed, 17 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
> > index e78430001f077..3bd5930e2769b 100644
> > --- a/drivers/gpu/drm/i915/display/intel_acpi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_acpi.c
> > @@ -20,6 +20,7 @@ static const guid_t intel_dsm_guid =
> >                 0xa8, 0x54, 0x0f, 0x13, 0x17, 0xb0, 0x1c, 0x2c);
> >
> >  #define INTEL_DSM_FN_GET_BIOS_DATA_FUNCS_SUPPORTED 0 /* No args */
> > +#define INTEL_DSM_FN_DP_IN_SWITCH_TO_DGFX 20 /* No args */
> >
> >  static const guid_t intel_dsm_guid2 =
> >       GUID_INIT(0x3e5b41c6, 0xeb1d, 0x4260,
> > @@ -187,6 +188,7 @@ void intel_dsm_get_bios_data_funcs_supported(struct drm_i915_private *i915)
> >       struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
> >       acpi_handle dhandle;
> >       union acpi_object *obj;
> > +     int supported = 0;
> >
> >       dhandle = ACPI_HANDLE(&pdev->dev);
> >       if (!dhandle)
> > @@ -194,8 +196,22 @@ void intel_dsm_get_bios_data_funcs_supported(struct drm_i915_private *i915)
> >
> >       obj = acpi_evaluate_dsm(dhandle, &intel_dsm_guid2, INTEL_DSM_REVISION_ID,
> >                               INTEL_DSM_FN_GET_BIOS_DATA_FUNCS_SUPPORTED, NULL);
> > -     if (obj)
> > +     if (obj) {
> > +             if (obj->type == ACPI_TYPE_INTEGER)
> > +                     supported = obj->integer.value;
> > +
> >               ACPI_FREE(obj);
> > +     }
> > +
> > +     /* Tiger Lake H DP-IN Boot Time Switching from iGfx to dGfx */
> > +     if (supported & BIT(20)) {
> > +             obj = acpi_evaluate_dsm(dhandle, &intel_dsm_guid2,
> > +                                     INTEL_DSM_REVISION_ID,
> > +                                     INTEL_DSM_FN_DP_IN_SWITCH_TO_DGFX,
> > +                                     NULL);
> > +             if (obj)
> > +                     ACPI_FREE(obj);
> > +     }
> >  }
> >
> >  /*
>
> --
> Jani Nikula, Intel Open Source Graphics Center