Re: [PATCH v5 07/17] drm/i915/hdcp: Enable HDCP 1.4 stream encryption

[Ramalingam C <ramalingam.c@intel.com>]

On 2020-11-11 at 11:50:41 +0530, Anshuman Gupta wrote:
> Enable HDCP 1.4 DP MST stream encryption.
> 
> Enable stream encryption once encryption is enabled on
> the DP transport driving the link for each stream which
> has requested encryption.
> 
> Disable stream encryption for each stream that no longer
> requires encryption before disabling HDCP encryption on
> the link.
> 
> v2:
> - Added debug print for stream encryption.
> - Disable the hdcp on port after disabling last stream
>   encryption.
> v3:
> - Cosmetic change, removed the value less comment. [Uma]
> v4:
> - Split the Gen12 HDCP enablement patch. [Ram]
> - Add connector details in drm_err.
> 
> Cc: Ramalingam C <ramalingam.c@intel.com>
> Reviewed-by: Uma Shankar <uma.shankar@intel.com>
> Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hdcp.c | 45 ++++++++++++++++-------
>  1 file changed, 31 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
> index 0322a83c151d..e12bd0ac9fb5 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> @@ -612,7 +612,12 @@ int intel_hdcp_auth_downstream(struct intel_connector *connector)
>  	return ret;
>  }
>  
> -/* Implements Part 1 of the HDCP authorization procedure */
> +/*
> + * Implements Part 1 of the HDCP authorization procedure.
> + * Authentication Part 1 steps for Multi-stream DisplayPort.
> + * Step 1. Auth Part 1 sequence on the driving MST Trasport Link.
> + * Step 2. Enable encryption for each stream that requires encryption.
> +1*/
IMO this function is generic for SST and MST. Why do we document only
for MST at the top of the function? We can remove them.
>  static int intel_hdcp_auth(struct intel_connector *connector)
>  {
>  	struct intel_digital_port *dig_port = intel_attached_dig_port(connector);
> @@ -766,10 +771,17 @@ static int intel_hdcp_auth(struct intel_connector *connector)
>  		return -ETIMEDOUT;
>  	}
>  
> -	/*
> -	 * XXX: If we have MST-connected devices, we need to enable encryption
> -	 * on those as well.
> -	 */
> +	/* DP MST Auth Part 1 Step 2.a and Step 2.b */
> +	if (shim->stream_encryption) {
> +		ret = shim->stream_encryption(connector, true);
> +		if (ret) {
> +			drm_err(&dev_priv->drm, "[CONNECTOR:%d:%s] Failed to enable HDCP 1.4 stream enc\n",
All the existing error messgae has the %s:%d, why are we changing it
here? Could we retain the uniformity?
> +				connector->base.base.id, connector->base.name);
> +			return ret;
> +		}
> +		drm_dbg_kms(&dev_priv->drm, "HDCP 1.4 transcoder: %s stream encrypted\n",
> +			    transcoder_name(hdcp->stream_transcoder));
> +	}
>  
>  	if (repeater_present)
>  		return intel_hdcp_auth_downstream(connector);
> @@ -791,18 +803,23 @@ static int _intel_hdcp_disable(struct intel_connector *connector)
>  	drm_dbg_kms(&dev_priv->drm, "[%s:%d] HDCP is being disabled...\n",
>  		    connector->base.name, connector->base.base.id);
>  
> +	if (hdcp->shim->stream_encryption) {
> +		ret = hdcp->shim->stream_encryption(connector, false);
> +		if (ret) {
> +			drm_err(&dev_priv->drm, "[CONNECTOR:%d:%s] Failed to disable HDCP 1.4 stream enc\n",
same here. remove CONNECTOR ?
> +				connector->base.base.id, connector->base.name);
> +			return ret;
> +		}
> +		drm_dbg_kms(&dev_priv->drm, "HDCP 1.4 transcoder: %s stream encryption disabled\n",
> +			    transcoder_name(hdcp->stream_transcoder));
> +	}
> +
>  	/*
> -	 * If there are other connectors on this port using HDCP, don't disable
> -	 * it. Instead, toggle the HDCP signalling off on that particular
> -	 * connector/pipe and exit.
> +	 * If there are other connectors on this port using HDCP, don't disable it.
> +	 * Repeat steps 1-2 for each stream that no longer requires encryption.
What is this steps 1-2 here!? Here you are not disabling if other
streams are encrpted. May be you want to put something like "Untill all
steams of MST stopped encrypting, dont disable the port encryption"

-Ram
>  	 */
> -	if (dig_port->num_hdcp_streams > 0) {
> -		ret = hdcp->shim->toggle_signalling(dig_port,
> -						    cpu_transcoder, false);
> -		if (ret)
> -			DRM_ERROR("Failed to disable HDCP signalling\n");
> +	if (dig_port->num_hdcp_streams > 0)
>  		return ret;
> -	}
>  
>  	hdcp->hdcp_encrypted = false;
>  	intel_de_write(dev_priv, HDCP_CONF(dev_priv, cpu_transcoder, port), 0);
> -- 
> 2.26.2
> 
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