[PATCH] drm/i915/hdcp: Add the loop only for DP encoders

[Borah, Chaitanya Kumar]

> -----Original Message-----
> From: Kandpal, Suraj <suraj.kandpal at intel.com>
> Sent: Wednesday, October 30, 2024 8:23 AM
> To: intel-xe at lists.freedesktop.org; intel-gfx at lists.freedesktop.org
> Cc: Kandpal, Suraj <suraj.kandpal at intel.com>; Borah, Chaitanya Kumar
> <chaitanya.kumar.borah at intel.com>
> Subject: [PATCH] drm/i915/hdcp: Add the loop only for DP encoders
> 
> Add the loop on the first read/write we do to give docks and dp encoders
> some extra time to get their HDCP DPCD registers ready only for DP/DPMST
> encoders as this issue is only observed here no need to burden other
> encoders with extra retries as this causes the HDMI connector to have some
> other timing issue and fails HDCP authentication.
> 
> --v2
> -Add intent of patch [Chaitanya]
> -Add reasoning for loop [Jani]
> -Make sure we forfiet the 50ms wait for non DP/DPMST encoders.
> 
> Fixes: 9d5a05f86d2f ("drm/i915/hdcp: Retry first read and writes to
> downstream")
> Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hdcp.c | 36 +++++++++++++++--------
>  1 file changed, 23 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c
> b/drivers/gpu/drm/i915/display/intel_hdcp.c
> index ed6aa87403e2..c8ba69c51cce 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> @@ -1503,6 +1503,8 @@ static int hdcp2_deauthenticate_port(struct
> intel_connector *connector)  static int
> hdcp2_authentication_key_exchange(struct intel_connector *connector)  {
>  	struct intel_display *display = to_intel_display(connector);
> +	struct intel_digital_port *dig_port =
> +		intel_attached_dig_port(connector);
>  	struct intel_hdcp *hdcp = &connector->hdcp;
>  	union {
>  		struct hdcp2_ake_init ake_init;
> @@ -1513,31 +1515,39 @@ static int
> hdcp2_authentication_key_exchange(struct intel_connector *connector)
>  	} msgs;
>  	const struct intel_hdcp_shim *shim = hdcp->shim;
>  	size_t size;
> -	int ret, i;
> +	bool is_dp_encoder;
> +	int ret, i, max_retries;
> 
>  	/* Init for seq_num */
>  	hdcp->seq_num_v = 0;
>  	hdcp->seq_num_m = 0;
> 
> +	is_dp_encoder =	intel_encoder_is_dp(&dig_port->base) ||
> +		intel_encoder_is_mst(&dig_port->base);
> +	if (is_dp_encoder)
> +		max_retries = 10;
> +	else
> +		max_retries = 1;
> +
>  	ret = hdcp2_prepare_ake_init(connector, &msgs.ake_init);
>  	if (ret < 0)
>  		return ret;
> 
>  	/*
>  	 * Retry the first read and write to downstream at least 10 times
> -	 * with a 50ms delay if not hdcp2 capable(dock decides to stop
> advertising
> -	 * hdcp2 capability for some reason). The reason being that
> -	 * during suspend resume dock usually keeps the HDCP2 registers
> inaccesible
> -	 * causing AUX error. This wouldn't be a big problem if the userspace
> -	 * just kept retrying with some delay while it continues to play low
> -	 * value content but most userpace applications end up throwing an
> error
> -	 * when it receives one from KMD. This makes sure we give the dock
> -	 * and the sink devices to complete its power cycle and then try HDCP
> -	 * authentication. The values of 10 and delay of 50ms was decided
> based
> -	 * on multiple trial and errors.
> +	 * with a 50ms delay if not hdcp2 capable for DP/DPMST encoders
> +	 * (dock decides to stop advertising hdcp2 capability for some
> reason).
> +	 * The reason being that during suspend resume dock usually keeps
> the
> +	 * HDCP2 registers inaccesible causing AUX error. This wouldn't be a
> +	 * big problem if the userspace just kept retrying with some delay
> while
> +	 * it continues to play low value content but most userpace
> applications
> +	 * end up throwing an error when it receives one from KMD. This
> makes
> +	 * sure we give the dock and the sink devices to complete its power
> cycle
> +	 * and then try HDCP authentication. The values of 10 and delay of
> 50ms
> +	 * was decided based on multiple trial and errors.
>  	 */
> -	for (i = 0; i < 10; i++) {
> -		if (!intel_hdcp2_get_capability(connector)) {
> +	for (i = 0; i < max_retries; i++) {
> +		if (!intel_hdcp2_get_capability(connector) &&
> is_dp_encoder) {

Now I am a bit confused, if you are using this Boolean here. Do you still need different values for max_retries?

Regards

Chaitanya

>  			msleep(50);
>  			continue;
>  		}
> --
> 2.34.1