[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: Tuesday, October 29, 2024 2:23 PM
> To: intel-xe at lists.freedesktop.org; intel-gfx at lists.freedesktop.org
> Cc: Borah, Chaitanya Kumar <chaitanya.kumar.borah at intel.com>; Kandpal,
> Suraj <suraj.kandpal at intel.com>
> Subject: [PATCH] drm/i915/hdcp: Add the loop only for DP encoders
> 
> Add the loop on the first read and write only for DP/DPMST encoders as this
> issue is only observed here no need to burden other encoders with extra
> retries.

It would make the motivation of the patch clearer if we describe "this issue" here.

> 
> Fixes: 9d5a05f86d2f ("drm/i915/hdcp: Retry first read and writes to
> downstream")
> Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hdcp.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c
> b/drivers/gpu/drm/i915/display/intel_hdcp.c
> index ed6aa87403e2..fcfb5a9f303a 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;
> @@ -1513,12 +1515,18 @@ 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;
> +	int ret, i, max_retries;
> 
>  	/* Init for seq_num */
>  	hdcp->seq_num_v = 0;
>  	hdcp->seq_num_m = 0;
> 
> +	if (intel_encoder_is_dp(&dig_port->base) ||
> +	    intel_encoder_is_mst(&dig_port->base))
> +		max_retries = 10;
> +	else
> +		max_retries = 1;
> +
>  	ret = hdcp2_prepare_ake_init(connector, &msgs.ake_init);
>  	if (ret < 0)
>  		return ret;
> @@ -1536,7 +1544,7 @@ static int
> hdcp2_authentication_key_exchange(struct intel_connector *connector)
>  	 * authentication. The values of 10 and delay of 50ms was decided
> based
>  	 * on multiple trial and errors.
>  	 */

Perhaps this comment can use an update too.

Functionally LGTM.

Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah at intel.com>

> -	for (i = 0; i < 10; i++) {
> +	for (i = 0; i < max_retries; i++) {
>  		if (!intel_hdcp2_get_capability(connector)) {
>  			msleep(50);
>  			continue;
> --
> 2.34.1