Re: [Intel-gfx] [PATCH 1/2] drm/i915/opregion: add function to check if headless sku

["Souza, Jose" <jose.souza@intel.com>]

On Fri, 2022-06-03 at 13:14 +0000, Hogander, Jouni wrote:
> On Fri, 2022-06-03 at 15:43 +0300, Jani Nikula wrote:
> > On Fri, 03 Jun 2022, Jouni Högander <jouni.hogander@intel.com> wrote:
> > > Export headless sku bit (bit 13) from opregion->header->pcon as an
> > > interface to check if our device is headless configuration.
> > > 
> > > Bspec: 53441
> > > Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/display/intel_opregion.c | 12 ++++++++++++
> > >  drivers/gpu/drm/i915/display/intel_opregion.h |  7 +++++++
> > >  2 files changed, 19 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/display/intel_opregion.c
> > > b/drivers/gpu/drm/i915/display/intel_opregion.c
> > > index f31e8c3f8ce0..eab3f2e6b786 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_opregion.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_opregion.c
> > > @@ -53,6 +53,8 @@
> > >  #define MBOX_ASLE_EXT		BIT(4)	/* Mailbox #5 */
> > >  #define MBOX_BACKLIGHT		BIT(5)	/* Mailbox #2
> > > (valid from v3.x) */
> > >  
> > > +#define PCON_HEADLESS_SKU	BIT(13)
> > 
> > Here we go again.
> > 
> > What does headless mean here? The spec does not say. Does it have
> > display hardware? Apparently yes, since otherwise we wouldn't be
> > here.
> 
> This is for hybrid setup with several display hw and the panel wont be
> connected into device driven by i915 driver.
> 
> > We have INTEL_DISPLAY_ENABLED() which should do the right thing when
> > you
> > do have display hardware and have done output setup etc. but want to
> > force them disconnected, i.e. you take the hardware over properly,
> > but
> > put it to sleep for power savings.
> > 
> > Maybe we should bolt this opregion check in that macro?
> > 
> > Maybe we need to use INTEL_DISPLAY_ENABLED() also to prevent polling.
> 
> Thank you for pointing this out. HAS_DISPLAY I already notice and it's
> not suitable for what we want here. I think bolting this check into
> INTEL_DISPLAY_ENABLED as you suggested is enough. That will prevent
> waking up the hw into D0 state for polling.

A headless sku should not have any DDI ports enabled, much easier check for that.

> 
> > 
> > I certainly would not want to add another mode that's separate from
> > HAS_DISPLAY() and INTEL_DISPLAY_ENABLED().
> 
> No need for this. I think we can go with INTEL_DISPLAY_ENABLED.
> > 
> > > +
> > >  struct opregion_header {
> > >  	u8 signature[16];
> > >  	u32 size;
> > > @@ -1135,6 +1137,16 @@ struct edid *intel_opregion_get_edid(struct
> > > intel_connector *intel_connector)
> > >  	return new_edid;
> > >  }
> > >  
> > > +bool intel_opregion_headless_sku(struct drm_i915_private *i915)
> > > +{
> > > +	struct intel_opregion *opregion = &i915->opregion;
> > > +
> > > +	if (!opregion->header)
> > > +		return false;
> > > +
> > > +	return opregion->header->pcon & PCON_HEADLESS_SKU;
> > 
> > We should probably start checking for opregion version for this stuff
> > too.
> > 
> 
> Yes, I will do this change.
> 
> > 
> > BR,
> > Jani.
> > 
> > > +}
> > > +
> > >  void intel_opregion_register(struct drm_i915_private *i915)
> > >  {
> > >  	struct intel_opregion *opregion = &i915->opregion;
> > > diff --git a/drivers/gpu/drm/i915/display/intel_opregion.h
> > > b/drivers/gpu/drm/i915/display/intel_opregion.h
> > > index 82cc0ba34af7..5ad96e1d8278 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_opregion.h
> > > +++ b/drivers/gpu/drm/i915/display/intel_opregion.h
> > > @@ -76,6 +76,8 @@ int intel_opregion_notify_adapter(struct
> > > drm_i915_private *dev_priv,
> > >  int intel_opregion_get_panel_type(struct drm_i915_private
> > > *dev_priv);
> > >  struct edid *intel_opregion_get_edid(struct intel_connector
> > > *connector);
> > >  
> > > +bool intel_opregion_headless_sku(struct drm_i915_private *i915);
> > > +
> > >  #else /* CONFIG_ACPI*/
> > >  
> > >  static inline int intel_opregion_setup(struct drm_i915_private
> > > *dev_priv)
> > > @@ -127,6 +129,11 @@ intel_opregion_get_edid(struct intel_connector
> > > *connector)
> > >  	return NULL;
> > >  }
> > >  
> > > +bool intel_opregion_headless_sku(struct drm_i915_private *i915)
> > > +{
> > > +	return false;
> > > +}
> > > +
> > >  #endif /* CONFIG_ACPI */
> > >  
> > >  #endif
>