[PATCH] drm/i915/hdcp: Use HDCP2_STREAM_STATUS to verify content type status

[Kandpal, Suraj]

> -----Original Message-----
> From: Jani Nikula <jani.nikula at linux.intel.com>
> Sent: Thursday, June 19, 2025 2:14 PM
> To: Kandpal, Suraj <suraj.kandpal at intel.com>; intel-xe at lists.freedesktop.org;
> intel-gfx at lists.freedesktop.org
> Cc: Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>; Kandpal, Suraj
> <suraj.kandpal at intel.com>
> Subject: Re: [PATCH] drm/i915/hdcp: Use HDCP2_STREAM_STATUS to verify
> content type status
> 
> On Thu, 19 Jun 2025, Suraj Kandpal <suraj.kandpal at intel.com> wrote:
> > From PTL we need to move to using HDCP2_STREAM_STATUS to check if the
> > written content type info is the same as we expect since
> > HDCP2_AUTH_STREAM is inaccessible to us now.
> 
> The commit message talks about "verify" and "check", but in reality it's just a
> warning and move on.
> 
> When can this happen?

Yes its basically just a warn will fix the language here
Also can happen when the data sent by driver to gsc gets corrupted and writes the wrong stream status info.

> 
> > Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 13 ++++++++++---
> >  1 file changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
> > b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
> > index 7bd775fb65a0..131fc0cae13b 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
> > @@ -806,9 +806,11 @@ intel_dp_mst_hdcp2_stream_encryption(struct
> intel_connector *connector,
> >  	enum port port = dig_port->base.port;
> >  	int ret;
> >
> > -	drm_WARN_ON(display->drm, enable &&
> > -		    !!(intel_de_read(display, HDCP2_AUTH_STREAM(display,
> cpu_transcoder, port))
> > -		    & AUTH_STREAM_TYPE) != data->streams[0].stream_type);
> > +	if (DISPLAY_VER(display) < 30)
> > +		drm_WARN_ON(display->drm, enable &&
> > +			    !!(intel_de_read(display,
> > +			    HDCP2_AUTH_STREAM(display, cpu_transcoder,
> port))
> > +			    & AUTH_STREAM_TYPE) != data-
> >streams[0].stream_type);
> 
> As a side note, can we please stop shoving complex intel_de_reads() inside a
> WARN_ON()? Separate the read and conditions for the warn.
> 
> Moreover, stream_type is u8, and it's compared some boolean logic.


Will send a separate patch fixing this as a part of this series
> 
> >
> >  	ret = intel_dp_mst_toggle_hdcp_stream_select(connector, enable);
> >  	if (ret)
> > @@ -824,6 +826,11 @@ intel_dp_mst_hdcp2_stream_encryption(struct
> intel_connector *connector,
> >  		return -ETIMEDOUT;
> >  	}
> >
> > +	if (DISPLAY_VER(display) >= 30)
> > +		drm_WARN_ON(display->drm, enable &&
> > +			    !!(intel_de_read(display,
> > +			    HDCP2_STREAM_STATUS(display, cpu_transcoder,
> port))
> > +			    & STREAM_TYPE_STATUS) != data-
> >streams[0].stream_type);
> 
> And this is now duplicated in two places.

It is reading a different register and this needs to happen at different places to since STREAM_STATUS is only really reliable once
It indicates encryption is enabled

Regards,
Suraj Kandpal

> 
> Please deduplicate and simplify.
> 
> BR,
> Jani.
> 
> >  	return 0;
> >  }
> 
> --
> Jani Nikula, Intel