Re: [PATCH v2 3/5] drm/i915: terminate reauth at stream management failure

Sean Paul
2020-02-18T15:35:00Z

On Wed, Feb 12, 2020 at 03:59:40PM +0530, Ramalingam C wrote:
> As per the HDCP2.2 compliance test 1B-10 expectation, when stream
> management for a repeater fails, we retry thrice and when it fails
> in all retries, HDCP2.2 reauthentication aborted at kernel.
>
> v2:
> seq_num_m++ is extended for steam management failures too.[Anshuman]
> v3:
> use drm_dbg_kms instead of DRM_DEBUG_KMS [Anshuman]
> v4:
> dev_priv is used as i915 [JaniN]
>
> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
> ---
> drivers/gpu/drm/i915/display/intel_hdcp.c | 75 ++++++++++++++---------
> 1 file changed, 46 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
> index 30e0a3aa9d57..b24d12efae0a 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> @@ -1380,7 +1380,7 @@ static int hdcp2_session_key_exchange(struct intel_connector *connector)
> }
>
> static
> -int hdcp2_propagate_stream_management_info(struct intel_connector *connector)
> +int _hdcp2_propagate_stream_management_info(struct intel_connector *connector)
> {
> struct intel_digital_port *intel_dig_port = intel_attached_dig_port(connector);
> struct intel_hdcp *hdcp = &connector->hdcp;
> @@ -1406,28 +1406,25 @@ int hdcp2_propagate_stream_management_info(struct intel_connector *connector)
> ret = shim->write_2_2_msg(intel_dig_port, &msgs.stream_manage,
> sizeof(msgs.stream_manage));
> if (ret < 0)
> - return ret;
> + goto err_exit;
>
> ret = shim->read_2_2_msg(intel_dig_port, HDCP_2_2_REP_STREAM_READY,
> &msgs.stream_ready, sizeof(msgs.stream_ready));
> if (ret < 0)
> - return ret;
> + goto err_exit;
>
> hdcp->port_data.seq_num_m = hdcp->seq_num_m;
> hdcp->port_data.streams[0].stream_type = hdcp->content_type;
> -
> ret = hdcp2_verify_mprime(connector, &msgs.stream_ready);
> - if (ret < 0)
> - return ret;
>
> +err_exit:

This isn't exclusively an error condition, I'd rather it named 'out' instead.

> hdcp->seq_num_m++;
> -
> if (hdcp->seq_num_m > HDCP_2_2_SEQ_NUM_MAX) {
> DRM_DEBUG_KMS("seq_num_m roll over.\n");
> - return -1;
> + ret = -1;

What does -1 mean? Please use an errno

> }
>
> - return 0;
> + return ret;
> }
>
> static
> @@ -1492,17 +1489,6 @@ int hdcp2_authenticate_repeater_topology(struct intel_connector *connector)
> return 0;
> }
>
> -static int hdcp2_authenticate_repeater(struct intel_connector *connector)
> -{
> - int ret;
> -
> - ret = hdcp2_authenticate_repeater_topology(connector);
> - if (ret < 0)
> - return ret;
> -
> - return hdcp2_propagate_stream_management_info(connector);
> -}
> -
> static int hdcp2_authenticate_sink(struct intel_connector *connector)
> {
> struct intel_digital_port *intel_dig_port = intel_attached_dig_port(connector);
> @@ -1537,18 +1523,13 @@ static int hdcp2_authenticate_sink(struct intel_connector *connector)
> }
>
> if (hdcp->is_repeater) {
> - ret = hdcp2_authenticate_repeater(connector);
> + ret = hdcp2_authenticate_repeater_topology(connector);
> if (ret < 0) {
> DRM_DEBUG_KMS("Repeater Auth Failed. Err: %d\n", ret);
> return ret;
> }
> }
>
> - hdcp->port_data.streams[0].stream_type = hdcp->content_type;
> - ret = hdcp2_authenticate_port(connector);
> - if (ret < 0)
> - return ret;
> -
> return ret;
> }
>
> @@ -1626,14 +1607,50 @@ static int hdcp2_disable_encryption(struct intel_connector *connector)
> return ret;
> }
>
> +static int
> +hdcp2_propagate_stream_management_info(struct intel_connector *connector)
> +{
> + struct drm_i915_private *i915 = to_i915(connector->base.dev);
> + int i, tries = 3, ret;
> +
> + if (!connector->hdcp.is_repeater)
> + return 0;
> +
> + for (i = 0; i < tries; i++) {
> + ret = _hdcp2_propagate_stream_management_info(connector);
> + if (!ret)
> + break;
> +
> + drm_dbg_kms(&i915->drm,
> + "HDCP2 stream management %d of %d Failed.(%d)\n",
> + i + 1, tries, ret);
> + }
> +
> + return ret;
> +}
> +
> static int hdcp2_authenticate_and_encrypt(struct intel_connector *connector)
> {
> + struct drm_i915_private *i915 = to_i915(connector->base.dev);
> + struct intel_hdcp *hdcp = &connector->hdcp;
> int ret, i, tries = 3;
>
> for (i = 0; i < tries; i++) {
> ret = hdcp2_authenticate_sink(connector);
> - if (!ret)
> - break;
> + if (!ret) {
> + ret = hdcp2_propagate_stream_management_info(connector);
> + if (!ret) {
> + hdcp->port_data.streams[0].stream_type =
> + hdcp->content_type;
> + ret = hdcp2_authenticate_port(connector);
> + if (!ret)
> + break;
> + } else {
> + drm_dbg_kms(&i915->drm,
> + "HDCP2 stream management failed\n");

Please print ret values on failures, always.

> + break;
> + }
> + }

The nesting here is a bit awkward. How about:

if (!ret) {
ret = hdcp2_propagate_stream_management_info(connector);
if (ret) {
drm_dbg_kms(&i915->drm,
"HDCP2 stream mgmt fail %d\n", ret);
break;
}

hdcp->port_data.streams[0].stream_type =
hdcp->content_type;
ret = hdcp2_authenticate_port(connector);
if (ret)
drm_dbg_kms(&i915->drm,
"HDCP2 auth port failed %d\n", ret);
else
break;
}

>
> /* Clearing the mei hdcp session */
> DRM_DEBUG_KMS("HDCP2.2 Auth %d of %d Failed.(%d)\n",
> @@ -1642,7 +1659,7 @@ static int hdcp2_authenticate_and_encrypt(struct intel_connector *connector)
> DRM_DEBUG_KMS("Port deauth failed.\n");
> }
>
> - if (i != tries) {
> + if (!ret) {
> /*
> * Ensuring the required 200mSec min time interval between
> * Session Key Exchange and encryption.
> --
> 2.20.1
>
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--
Sean Paul, Software Engineer, Google / Chromium OS