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

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

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.

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.

I certainly would not want to add another mode that's separate from
HAS_DISPLAY() and 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.


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

-- 
Jani Nikula, Intel Open Source Graphics Center