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From:   "Kandpal, Suraj" <suraj.kandpal@intel.com>
To:     Mark Yacoub <markyacoub@chromium.org>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        "Vivi, Rodrigo" <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
CC:     "seanpaul@chromium.org" <seanpaul@chromium.org>,
        "dianders@chromium.org" <dianders@chromium.org>,
        "dmitry.baryshkov@linaro.org" <dmitry.baryshkov@linaro.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "freedreno@lists.freedesktop.org" <freedreno@lists.freedesktop.org>,
        "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>,
        "Nikula, Jani" <jani.nikula@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v9 02/10] drm/hdcp: Avoid changing crtc state in hdcp
 atomic check
Thread-Topic: [PATCH v9 02/10] drm/hdcp: Avoid changing crtc state in hdcp
 atomic check
Thread-Index: AQHZbKrltyq9qSpqzE28yFk5gVXHC68wlOcA
Date:   Tue, 18 Apr 2023 05:37:33 +0000
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 <20230411192134.508113-3-markyacoub@google.com>
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>=20
> From: Sean Paul <seanpaul@chromium.org>
>=20
> Instead of forcing a modeset in the hdcp atomic check, rename to
> drm_hdcp_has_changed and return true if the content protection value is
> changing and let the driver decide whether a modeset is required or not.
>=20
> Acked-by: Jani Nikula <jani.nikula@intel.com>
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Signed-off-by: Sean Paul <seanpaul@chromium.org>
> Signed-off-by: Mark Yacoub <markyacoub@chromium.org>
>=20
> ---
> Changes in v2:
> -None
> Changes in v3:
> -None
> Changes in v4:
> -None
> Changes in v5:
> -None
> Changes in v6:
> -Rebase: modifications in drm_hdcp_helper.c instead of drm_hdcp.c
> Changes in v7:
> -Renamed the function from drm_hdcp_atomic_check to
> drm_hdcp_has_changed (Dmitry Baryshkov)
>=20
>  drivers/gpu/drm/display/drm_hdcp_helper.c   | 39 ++++++++++++++-------
>  drivers/gpu/drm/i915/display/intel_atomic.c |  6 ++--
>  include/drm/display/drm_hdcp_helper.h       |  2 +-
>  3 files changed, 30 insertions(+), 17 deletions(-)
>=20
> diff --git a/drivers/gpu/drm/display/drm_hdcp_helper.c
> b/drivers/gpu/drm/display/drm_hdcp_helper.c
> index 7ca390b3ea106..34baf2b97cd87 100644
> --- a/drivers/gpu/drm/display/drm_hdcp_helper.c
> +++ b/drivers/gpu/drm/display/drm_hdcp_helper.c
> @@ -422,18 +422,21 @@ void drm_hdcp_update_content_protection(struct
> drm_connector *connector,
> EXPORT_SYMBOL(drm_hdcp_update_content_protection);
>=20
>  /**
> - * drm_hdcp_atomic_check - Helper for drivers to call during connector-
> >atomic_check
> + * drm_hdcp_has_changed - Helper for drivers to call during
> + connector->atomic_check
>   *
>   * @state: pointer to the atomic state being checked
>   * @connector: drm_connector on which content protection state needs an
> update
>   *
>   * This function can be used by display drivers to perform an atomic che=
ck
> on the
> - * hdcp state elements. If hdcp state has changed, this function will se=
t
> - * mode_changed on the crtc driving the connector so it can update its
> hardware
> - * to match the hdcp state.
> + * hdcp state elements. If hdcp state has changed in a manner which
> + requires the
> + * driver to enable or disable content protection, this function will
> + return
> + * true.
> + *
> + * Returns:
> + * true if the driver must enable/disable hdcp, false otherwise
>   */
> -void drm_hdcp_atomic_check(struct drm_connector *connector,
> -			   struct drm_atomic_state *state)
> +bool drm_hdcp_has_changed(struct drm_connector *connector,
> +			  struct drm_atomic_state *state)
>  {
>  	struct drm_connector_state *new_conn_state, *old_conn_state;
>  	struct drm_crtc_state *new_crtc_state; @@ -450,19 +453,31 @@
> void drm_hdcp_atomic_check(struct drm_connector *connector,
>  		 * If the connector is being disabled with CP enabled, mark it
>  		 * desired so it's re-enabled when the connector is brought
> back
>  		 */
> -		if (old_hdcp =3D=3D
> DRM_MODE_CONTENT_PROTECTION_ENABLED)
> +		if (old_hdcp =3D=3D
> DRM_MODE_CONTENT_PROTECTION_ENABLED) {
>  			new_conn_state->content_protection =3D
>=20
> 	DRM_MODE_CONTENT_PROTECTION_DESIRED;
> -		return;
> +			return true;
> +		}
> +		return false;
>  	}
>=20
>  	new_crtc_state =3D
>  		drm_atomic_get_new_crtc_state(state, new_conn_state-
> >crtc);
>  	if (drm_atomic_crtc_needs_modeset(new_crtc_state) &&
>  	    (old_hdcp =3D=3D DRM_MODE_CONTENT_PROTECTION_ENABLED &&
> -	     new_hdcp !=3D DRM_MODE_CONTENT_PROTECTION_UNDESIRED))
> +	     new_hdcp !=3D DRM_MODE_CONTENT_PROTECTION_UNDESIRED))
> {
>  		new_conn_state->content_protection =3D
>  			DRM_MODE_CONTENT_PROTECTION_DESIRED;
> +		return true;
> +	}
> +
> +	/*
> +	 * Coming back from UNDESIRED state, CRTC change or re-
> enablement requires
> +	 * the driver to try CP enable.
> +	 */
> +	if (new_hdcp =3D=3D DRM_MODE_CONTENT_PROTECTION_DESIRED &&
> +	    new_conn_state->crtc !=3D old_conn_state->crtc)
> +		return true;
>=20
>  	/*
>  	 * Nothing to do if content type is unchanged and one of:
> @@ -477,9 +492,9 @@ void drm_hdcp_atomic_check(struct drm_connector
> *connector,
>  	     new_hdcp =3D=3D DRM_MODE_CONTENT_PROTECTION_DESIRED)) {
>  		if (old_conn_state->hdcp_content_type =3D=3D
>  		    new_conn_state->hdcp_content_type)
> -			return;
> +			return false;
>  	}
>=20
> -	new_crtc_state->mode_changed =3D true;
> +	return true;
>  }

So previously in hdcp_atomic_check we decided if a mode change was required=
 only after going through two different checks
if (drm_atomic_crtc_needs_modeset(new_crtc_state) &&
 (old_hdcp =3D=3D DRM_MODE_CONTENT_PROTECTION_ENABLED &&
     new_hdcp !=3D DRM_MODE_CONTENT_PROTECTION_UNDESIRED))

and=20

if (old_hdcp =3D=3D new_hdcp ||
	    (old_hdcp =3D=3D DRM_MODE_CONTENT_PROTECTION_DESIRED &&
	     new_hdcp =3D=3D DRM_MODE_CONTENT_PROTECTION_ENABLED) ||
	    (old_hdcp =3D=3D DRM_MODE_CONTENT_PROTECTION_ENABLED &&
	     new_hdcp =3D=3D DRM_MODE_CONTENT_PROTECTION_DESIRED))

then we decided if mode needs to change or not but now we are returning mod=
e_changed
as true if either of the conditions are met
maybe we can have a bool variable that gets assigned true or false and is r=
eturned only at the end
of the function where we previously changed mode_changed to true

Regards,
Suraj Kandpal

> -EXPORT_SYMBOL(drm_hdcp_atomic_check);
> +EXPORT_SYMBOL(drm_hdcp_has_changed);
> diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c
> b/drivers/gpu/drm/i915/display/intel_atomic.c
> index e9d00b6a63d39..23a6ba315a22e 100644
> --- a/drivers/gpu/drm/i915/display/intel_atomic.c
> +++ b/drivers/gpu/drm/i915/display/intel_atomic.c
> @@ -124,8 +124,6 @@ int intel_digital_connector_atomic_check(struct
> drm_connector *conn,
>  		to_intel_digital_connector_state(old_state);
>  	struct drm_crtc_state *crtc_state;
>=20
> -	drm_hdcp_atomic_check(conn, state);
> -
>  	if (!new_state->crtc)
>  		return 0;
>=20
> @@ -141,8 +139,8 @@ int intel_digital_connector_atomic_check(struct
> drm_connector *conn,
>  	    new_conn_state->base.picture_aspect_ratio !=3D old_conn_state-
> >base.picture_aspect_ratio ||
>  	    new_conn_state->base.content_type !=3D old_conn_state-
> >base.content_type ||
>  	    new_conn_state->base.scaling_mode !=3D old_conn_state-
> >base.scaling_mode ||
> -	    new_conn_state->base.privacy_screen_sw_state !=3D
> old_conn_state->base.privacy_screen_sw_state ||
> -	    !drm_connector_atomic_hdr_metadata_equal(old_state,
> new_state))
> +	    !drm_connector_atomic_hdr_metadata_equal(old_state,
> new_state) ||
> +	    drm_hdcp_has_changed(conn, state))
>  		crtc_state->mode_changed =3D true;
>=20
>  	return 0;
> diff --git a/include/drm/display/drm_hdcp_helper.h
> b/include/drm/display/drm_hdcp_helper.h
> index dd02b2e72a502..703421fcdf96c 100644
> --- a/include/drm/display/drm_hdcp_helper.h
> +++ b/include/drm/display/drm_hdcp_helper.h
> @@ -19,7 +19,7 @@ int drm_hdcp_check_ksvs_revoked(struct drm_device
> *dev, u8 *ksvs, u32 ksv_count)  int
> drm_connector_attach_content_protection_property(struct drm_connector
> *connector,
>  						     bool hdcp_content_type);
>  void drm_hdcp_update_content_protection(struct drm_connector
> *connector, u64 val); -void drm_hdcp_atomic_check(struct drm_connector
> *connector,
> +bool drm_hdcp_has_changed(struct drm_connector *connector,
>  			   struct drm_atomic_state *state);
>=20
>  #endif
> --
> 2.40.0.577.gac1e443424-goog