Re: [PATCH v6 02/10] drm/hdcp: Avoid changing crtc state in hdcp atomic check

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On 18/01/2023 21:30, Mark Yacoub wrote:
> From: Sean Paul <seanpaul@chromium.org>
> 
> Instead of forcing a modeset in the hdcp atomic check, simply return
> true if the content protection value is changing and let the driver
> decide whether a modeset is required or not.

I don't think this is a good idea. All foo_atomic_check functions return 
an error code (or 0 if atomic check passes). Making 
drm_hpcp_atomic_check return bool is against that custom and is a clear 
way to make one forget to notice that. Please rename function to remove 
possible confusion.

> 
> 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>
> Link: https://patchwork.freedesktop.org/patch/msgid/20210913175747.47456-3-sean@poorly.run #v1
> Link: https://patchwork.freedesktop.org/patch/msgid/20210915203834.1439-3-sean@poorly.run #v2
> Link: https://patchwork.freedesktop.org/patch/msgid/20211001151145.55916-3-sean@poorly.run #v3
> Link: https://patchwork.freedesktop.org/patch/msgid/20211105030434.2828845-3-sean@poorly.run #v4
> Link: https://patchwork.freedesktop.org/patch/msgid/20220411204741.1074308-3-sean@poorly.run #v5
> 
> 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
> 
> ---
>   drivers/gpu/drm/display/drm_hdcp_helper.c   | 33 +++++++++++++++------
>   drivers/gpu/drm/i915/display/intel_atomic.c |  6 ++--
>   include/drm/display/drm_hdcp_helper.h       |  2 +-
>   3 files changed, 27 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_hdcp_helper.c b/drivers/gpu/drm/display/drm_hdcp_helper.c
> index 7d910523b05f..a3896b0904b5 100644
> --- a/drivers/gpu/drm/display/drm_hdcp_helper.c
> +++ b/drivers/gpu/drm/display/drm_hdcp_helper.c
> @@ -428,11 +428,14 @@ EXPORT_SYMBOL(drm_hdcp_update_content_protection);
>    * @connector: drm_connector on which content protection state needs an update
>    *
>    * This function can be used by display drivers to perform an atomic check on the
> - * hdcp state elements. If hdcp state has changed, this function will set
> - * 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,
> +bool drm_hdcp_atomic_check(struct drm_connector *connector,
>   			   struct drm_atomic_state *state)
>   {
>   	struct drm_connector_state *new_conn_state, *old_conn_state;
> @@ -450,10 +453,12 @@ 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 == DRM_MODE_CONTENT_PROTECTION_ENABLED)
> +		if (old_hdcp == DRM_MODE_CONTENT_PROTECTION_ENABLED) {
>   			new_conn_state->content_protection =
>   				DRM_MODE_CONTENT_PROTECTION_DESIRED;
> -		return;
> +			return true;
> +		}
> +		return false;
>   	}
>   
>   	new_crtc_state =
> @@ -465,9 +470,19 @@ void drm_hdcp_atomic_check(struct drm_connector *connector,
>   	*/
>   	if (drm_atomic_crtc_needs_modeset(new_crtc_state) &&
>   	    (old_hdcp == DRM_MODE_CONTENT_PROTECTION_ENABLED &&
> -	     new_hdcp != DRM_MODE_CONTENT_PROTECTION_UNDESIRED))
> +	     new_hdcp != DRM_MODE_CONTENT_PROTECTION_UNDESIRED)) {
>   		new_conn_state->content_protection =
>   			DRM_MODE_CONTENT_PROTECTION_DESIRED;
> +		return true;
> +	}
> +
> +	/*
> +	 * Coming back from disable or changing CRTC with DESIRED state requires
> +	 * that the driver try CP enable.
> +	 */
> +	if (new_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
> +	    new_conn_state->crtc != old_conn_state->crtc)
> +		return true;
>   
>   	/*
>   	 * Nothing to do if content type is unchanged and one of:
> @@ -482,9 +497,9 @@ void drm_hdcp_atomic_check(struct drm_connector *connector,
>   	     new_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED)) {
>   		if (old_conn_state->hdcp_content_type ==
>   		    new_conn_state->hdcp_content_type)
> -			return;
> +			return false;
>   	}
>   
> -	new_crtc_state->mode_changed = true;
> +	return true;
>   }
>   EXPORT_SYMBOL(drm_hdcp_atomic_check);
> diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c b/drivers/gpu/drm/i915/display/intel_atomic.c
> index 8a473199c4bf..a2067cbae2d5 100644
> --- a/drivers/gpu/drm/i915/display/intel_atomic.c
> +++ b/drivers/gpu/drm/i915/display/intel_atomic.c
> @@ -123,8 +123,6 @@ int intel_digital_connector_atomic_check(struct drm_connector *conn,
>   		to_intel_digital_connector_state(old_state);
>   	struct drm_crtc_state *crtc_state;
>   
> -	drm_hdcp_atomic_check(conn, state);
> -
>   	if (!new_state->crtc)
>   		return 0;
>   
> @@ -140,8 +138,8 @@ int intel_digital_connector_atomic_check(struct drm_connector *conn,
>   	    new_conn_state->base.picture_aspect_ratio != old_conn_state->base.picture_aspect_ratio ||
>   	    new_conn_state->base.content_type != old_conn_state->base.content_type ||
>   	    new_conn_state->base.scaling_mode != old_conn_state->base.scaling_mode ||
> -	    new_conn_state->base.privacy_screen_sw_state != 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_atomic_check(conn, state))
>   		crtc_state->mode_changed = true;
>   
>   	return 0;
> diff --git a/include/drm/display/drm_hdcp_helper.h b/include/drm/display/drm_hdcp_helper.h
> index dd02b2e72a50..cb2cc5002f65 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_atomic_check(struct drm_connector *connector,
>   			   struct drm_atomic_state *state);
>   
>   #endif

-- 
With best wishes
Dmitry