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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 29 Oct 2024, "Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com> wrote:
>> -----Original Message-----
>> From: Kandpal, Suraj <suraj.kandpal@intel.com>
>> Sent: Tuesday, October 29, 2024 2:23 PM
>> To: intel-xe@lists.freedesktop.org; intel-gfx@lists.freedesktop.org
>> Cc: Borah, Chaitanya Kumar <chaitanya.kumar.borah@intel.com>; Kandpal,
>> Suraj <suraj.kandpal@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.

Ditto for "the loop".

>
>> 
>> Fixes: 9d5a05f86d2f ("drm/i915/hdcp: Retry first read and writes to
>> downstream")
>> Signed-off-by: Suraj Kandpal <suraj.kandpal@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@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
>

-- 
Jani Nikula, Intel