[PATCH] drm/i915/hdcp: Disable HDCP Line Rekeying for HDCP2.2 on HDMI

[Kandpal, Suraj]

> -----Original Message-----
> From: Nikula, Jani <jani.nikula at intel.com>
> Sent: Tuesday, April 16, 2024 2:28 PM
> To: Kandpal, Suraj <suraj.kandpal at intel.com>; intel-gfx at lists.freedesktop.org
> Cc: Borah, Chaitanya Kumar <chaitanya.kumar.borah at intel.com>; Shankar,
> Uma <uma.shankar at intel.com>; Nautiyal, Ankit K
> <ankit.k.nautiyal at intel.com>; Kandpal, Suraj <suraj.kandpal at intel.com>
> Subject: Re: [PATCH] drm/i915/hdcp: Disable HDCP Line Rekeying for HDCP2.2
> on HDMI
> 
> On Tue, 16 Apr 2024, Suraj Kandpal <suraj.kandpal at intel.com> wrote:
> > Disable HDCP Line Rekeying when HDCP ver > 1.4 and when we are on
> HDMI
> > TMDS operation for DISPLAY_VER >= 14.
> >
> > --v2
> > -Wa to be mentioned in comments not in commit message [Jani] -Remove
> > blankline [Jani]
> >
> > Bspec: 49273
> > Bspec: 69964
> > Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_hdcp.c | 22 ++++++++++++++++++++++
> >  drivers/gpu/drm/i915/i915_reg.h           |  1 +
> >  2 files changed, 23 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c
> > b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > index d5ed4c7dfbc0..4b1833742245 100644
> > --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > @@ -30,6 +30,26 @@
> >  #define KEY_LOAD_TRIES	5
> >  #define HDCP2_LC_RETRY_CNT			3
> >
> > +/*
> > + * WA: 16022217614
> > + * Disable HDCP Line Rekeying when HDCP ver > 1.4
> > + * and when we are on HDMI TMDS operation
> > + * for DISPLAY_VEY >= 14.
> 
> Sorry to be nitpicking here, but we really don't want to duplicate in comments
> what the code is already saying.
> 
Would just mentioning the WA no. suffice or just drop the comment al together ?

Regards,
Suraj Kandpal

> BR,
> Jani.
> 
> > + */
> > +static void
> > +intel_hdcp_disable_hdcp_line_rekeying(struct intel_encoder *encoder,
> > +				      struct intel_hdcp *hdcp)
> > +{
> > +	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> > +
> > +	if (encoder->type != INTEL_OUTPUT_HDMI)
> > +		return;
> > +
> > +	if (DISPLAY_VER(dev_priv) >= 14)
> > +		intel_de_rmw(dev_priv, TRANS_DDI_FUNC_CTL(hdcp-
> >cpu_transcoder),
> > +			     TRANS_DDI_HDCP_LINE_REKEY_DISABLE, 1); }
> > +
> >  static int intel_conn_to_vcpi(struct intel_atomic_state *state,
> >  			      struct intel_connector *connector)  { @@ -2005,6
> +2025,8 @@
> > static int _intel_hdcp2_enable(struct intel_atomic_state *state,
> >  		    connector->base.base.id, connector->base.name,
> >  		    hdcp->content_type);
> >
> > +	intel_hdcp_disable_hdcp_line_rekeying(connector->encoder, hdcp);
> > +
> >  	ret = hdcp2_authenticate_and_encrypt(state, connector);
> >  	if (ret) {
> >  		drm_dbg_kms(&i915->drm, "HDCP2 Type%d  Enabling Failed.
> (%d)\n",
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h
> > b/drivers/gpu/drm/i915/i915_reg.h index 3f34efcd7d6c..fbf4623cd536
> > 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -5630,6 +5630,7 @@ enum skl_power_gate {
> >  #define  TRANS_DDI_EDP_INPUT_B_ONOFF	(5 << 12)
> >  #define  TRANS_DDI_EDP_INPUT_C_ONOFF	(6 << 12)
> >  #define  TRANS_DDI_EDP_INPUT_D_ONOFF	(7 << 12)
> > +#define  TRANS_DDI_HDCP_LINE_REKEY_DISABLE	REG_BIT(12)
> >  #define  TRANS_DDI_MST_TRANSPORT_SELECT_MASK
> 	REG_GENMASK(11, 10)
> >  #define  TRANS_DDI_MST_TRANSPORT_SELECT(trans)	\
> >  	REG_FIELD_PREP(TRANS_DDI_MST_TRANSPORT_SELECT_MASK,
> trans)
> 
> --
> Jani Nikula, Intel