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

[Kandpal, Suraj]

> -----Original Message-----
> From: Jani Nikula <jani.nikula at linux.intel.com>
> Sent: Wednesday, October 30, 2024 3:52 PM
> To: Borah, Chaitanya Kumar <chaitanya.kumar.borah at intel.com>; Kandpal,
> Suraj <suraj.kandpal at intel.com>; intel-xe at lists.freedesktop.org; intel-
> gfx at lists.freedesktop.org
> Subject: RE: [PATCH] drm/i915/hdcp: Add the loop only for DP encoders
> 
> On Wed, 30 Oct 2024, "Borah, Chaitanya Kumar"
> <chaitanya.kumar.borah at intel.com> wrote:
> >> -----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?
> 
> Even more confusing, if you get false for hdcp2 cap with HDMI, you'll continue
> with this stuff anyway?! What's the point in that?
> 
> BR,
> Jani.

You are right this check shouldn't have been added does not make any sense here


Regards,
Suraj Kandpal

> 
> >
> > Regards
> >
> > Chaitanya
> >
> >>  			msleep(50);
> >>  			continue;
> >>  		}
> >> --
> >> 2.34.1
> >
> 
> --
> Jani Nikula, Intel