Re: [PATCH v7 3/3] drm/bridge: it6505: handle HDCP request

[Sean Paul <sean@poorly.run>]

On Wed, Nov 23, 2022 at 10:05:29AM +0000, Hsin-Yi Wang wrote:
> it6505 supports HDCP 1.3, but current implementation lacks the update of
> HDCP status through drm_hdcp_update_content_protection().
> 
> it6505 default enables the HDCP. Remove this and only turn on when user
> requests it.
> 
> Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
> Reviewed-by: allen chen <allen.chen@ite.com.tw>
> ---
> v6->v7: remove enable hdcp by default.
> ---
>  drivers/gpu/drm/bridge/ite-it6505.c | 60 +++++++++++++++++++++++++++--
>  1 file changed, 57 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
> index 21a9b8422bda..93626698c31e 100644
> --- a/drivers/gpu/drm/bridge/ite-it6505.c
> +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> @@ -423,6 +423,7 @@ struct it6505 {
>  	struct extcon_dev *extcon;
>  	struct work_struct extcon_wq;
>  	int extcon_state;
> +	struct drm_connector *connector;
>  	enum drm_connector_status connector_status;
>  	enum link_train_status link_state;
>  	struct work_struct link_works;
> @@ -2159,9 +2160,6 @@ static void it6505_link_train_ok(struct it6505 *it6505)
>  		DRM_DEV_DEBUG_DRIVER(dev, "Enable audio!");
>  		it6505_enable_audio(it6505);
>  	}
> -
> -	if (it6505->hdcp_desired)
> -		it6505_start_hdcp(it6505);
>  }
>  
>  static void it6505_link_step_train_process(struct it6505 *it6505)
> @@ -2399,6 +2397,14 @@ static void it6505_irq_hdcp_done(struct it6505 *it6505)
>  
>  	DRM_DEV_DEBUG_DRIVER(dev, "hdcp done interrupt");
>  	it6505->hdcp_status = HDCP_AUTH_DONE;
> +	if (it6505->connector) {
> +		struct drm_device *drm_dev = it6505->connector->dev;
> +
> +		drm_modeset_lock(&drm_dev->mode_config.connection_mutex, NULL);
> +		drm_hdcp_update_content_protection(it6505->connector,
> +						   DRM_MODE_CONTENT_PROTECTION_ENABLED);
> +		drm_modeset_unlock(&drm_dev->mode_config.connection_mutex);
> +	}
>  	it6505_show_hdcp_info(it6505);
>  }
>  
> @@ -2931,6 +2937,7 @@ static void it6505_bridge_atomic_enable(struct drm_bridge *bridge,
>  	if (WARN_ON(!connector))
>  		return;
>  
> +	it6505->connector = connector;
>  	conn_state = drm_atomic_get_new_connector_state(state, connector);
>  
>  	if (WARN_ON(!conn_state))
> @@ -2974,6 +2981,7 @@ static void it6505_bridge_atomic_disable(struct drm_bridge *bridge,
>  
>  	DRM_DEV_DEBUG_DRIVER(dev, "start");
>  
> +	it6505->connector = NULL;
>  	if (it6505->powered) {
>  		it6505_drm_dp_link_set_power(&it6505->aux, &it6505->link,
>  					     DP_SET_POWER_D3);
> @@ -3028,6 +3036,50 @@ static struct edid *it6505_bridge_get_edid(struct drm_bridge *bridge,
>  	return edid;
>  }
>  
> +static int it6505_connector_atomic_check(struct it6505 *it6505,
> +					 struct drm_connector_state *state)
> +{
> +	struct device *dev = &it6505->client->dev;
> +	int cp = state->content_protection;
> +
> +	DRM_DEV_DEBUG_DRIVER(dev, "hdcp connector state:%d, curr hdcp state:%d",
> +			     cp, it6505->hdcp_status);
> +
> +	if (!it6505->hdcp_desired) {
> +		DRM_DEV_DEBUG_DRIVER(dev, "sink not support hdcp");
> +		return 0;
> +	}
> +
> +	if (it6505->hdcp_status == HDCP_AUTH_GOING)
> +		return -EINVAL;
> +
> +	if (cp == DRM_MODE_CONTENT_PROTECTION_UNDESIRED) {
> +		if (it6505->hdcp_status == HDCP_AUTH_DONE)
> +			it6505_stop_hdcp(it6505);

You shouldn't touch the hardware in atomic_check, this should be done in the
commit.

> +	} else if (cp == DRM_MODE_CONTENT_PROTECTION_DESIRED) {
> +		if (it6505->hdcp_status == HDCP_AUTH_IDLE &&
> +		    it6505->link_state == LINK_OK)
> +			it6505_start_hdcp(it6505);

Same here

> +	} else {
> +		if (it6505->hdcp_status == HDCP_AUTH_IDLE) {
> +			DRM_DEV_DEBUG_DRIVER(dev, "invalid to set hdcp enabled");
> +			return -EINVAL;
> +		}
> +	}

In general, I think there are a number of locking and state issues with this
approach. I had pulled all of this logic into a set of helpers [1], but the
patchset has gotten stale on the list. You might consider looking at patches 1-4
to see how the state and locking should be handled to avoid races.

Sean

[1] - https://lore.kernel.org/all/20220411204741.1074308-1-sean@poorly.run/

> +
> +	return 0;
> +}
> +
> +static int it6505_bridge_atomic_check(struct drm_bridge *bridge,
> +				      struct drm_bridge_state *bridge_state,
> +				      struct drm_crtc_state *crtc_state,
> +				      struct drm_connector_state *conn_state)
> +{
> +	struct it6505 *it6505 = bridge_to_it6505(bridge);
> +
> +	return it6505_connector_atomic_check(it6505, conn_state);
> +}
> +
>  static const struct drm_bridge_funcs it6505_bridge_funcs = {
>  	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
>  	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
> @@ -3035,6 +3087,7 @@ static const struct drm_bridge_funcs it6505_bridge_funcs = {
>  	.attach = it6505_bridge_attach,
>  	.detach = it6505_bridge_detach,
>  	.mode_valid = it6505_bridge_mode_valid,
> +	.atomic_check = it6505_bridge_atomic_check,
>  	.atomic_enable = it6505_bridge_atomic_enable,
>  	.atomic_disable = it6505_bridge_atomic_disable,
>  	.atomic_pre_enable = it6505_bridge_atomic_pre_enable,
> @@ -3354,6 +3407,7 @@ static int it6505_i2c_probe(struct i2c_client *client,
>  	it6505->bridge.type = DRM_MODE_CONNECTOR_DisplayPort;
>  	it6505->bridge.ops = DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID |
>  			     DRM_BRIDGE_OP_HPD;
> +	it6505->bridge.support_hdcp = true;
>  	drm_bridge_add(&it6505->bridge);
>  
>  	return 0;
> -- 
> 2.38.1.584.g0f3c55d4c2-goog
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS