[PATCH 1/2] drm/i915/hdcp: Do not use inline intel_de_read

[Kandpal, Suraj]

> -----Original Message-----
> From: Nikula, Jani <jani.nikula at intel.com>
> Sent: Thursday, June 19, 2025 4:29 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 1/2] drm/i915/hdcp: Do not use inline intel_de_read
> 
> On Thu, 19 Jun 2025, Suraj Kandpal <suraj.kandpal at intel.com> wrote:
> > Do not use intel_de_read() inline in the WARN_ON functions.
> > While we are at it make the comparision for stream_type u8 to u8.
> >
> > Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 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..3620f7853c8f 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
> > @@ -805,10 +805,13 @@ intel_dp_mst_hdcp2_stream_encryption(struct
> intel_connector *connector,
> >  	enum pipe pipe = (enum pipe)cpu_transcoder;
> >  	enum port port = dig_port->base.port;
> >  	int ret;
> > +	u32 val;
> > +	u8 stream_type;
> >
> > +	val = intel_de_read(display, HDCP2_AUTH_STREAM(display,
> cpu_transcoder, port));
> > +	stream_type = REG_FIELD_GET8(AUTH_STREAM_TYPE, val);
> 
> The size in GET8 is not really about the size of the field, it's about the size of
> the register/value, and how the field is defined.
> 
> It should be REG_FIELD_GET() for 32-bit registers.
> 
> But then should AUTH_STREAM_TYPE be defined via REG_GENMASK()?
> 
> #define   AUTH_STREAM_TYPE_MASK		REG_GENMASK(31, 31)
> 
> Would be more consistent:
> 
> 	stream_type = REG_FIELD_GET(AUTH_STREAM_TYPE_MASK, val);
> 
> >  	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);
> > +		    stream_type == data->streams[0].stream_type);
> 
> Comparing it like this certainly makes much more sense, but shouldn't it
> remain != instead of ==?

Right fixed these and sent a new version

Regards,
Suraj Kandpal

> 
> BR,
> Jani.
> 
> >
> >  	ret = intel_dp_mst_toggle_hdcp_stream_select(connector, enable);
> >  	if (ret)
> 
> --
> Jani Nikula, Intel