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

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Message-ID: <CAAd53p5=LqxKZGTARpvVCC2hcZP4aQPqjD6WszTDuQfv2owhfA@mail.gmail.com>
Date:   Mon, 26 Apr 2021 19:05:39 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Takashi Iwai <tiwai@...e.de>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/i915: Invoke BXT _DSM to enable MUX on HP
 Workstation laptops

On Fri, Apr 23, 2021 at 3:35 PM Jani Nikula <jani.nikula@...ux.intel.com> wrote:
>
> On Fri, 23 Apr 2021, Kai-Heng Feng <kai.heng.feng@...onical.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@...onical.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?

If there's no oppose, I'll change it to intel_hp_dsm_detect() in v2.
So far, I've only seen that DSM in HP platform.

>
> > +{
> > +     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.

Yes, because what it really does is flipping a bit in one GPIO, the
EC/hardware will change the MUX based on the GPIO bit.
So it doesn't have any ordering needs to be enforced.

>
> 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()?

OK, I'll put that in intel_modeset_init_hw() to cover both probe and
resume routines.

Kai-Heng


>
> >       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