[Intel-gfx] i915 MST HDCP code looks broken

[Intel-gfx] i915 MST HDCP code looks broken

[Ville Syrjälä]

Hi,

I took a quick peek at intel_dp_add_mst_connector() the other day and
noticed that it calls intel_dp_hdcp_init() and passes in the SST
dig_port. And digging in a bit further that seems to clobber all
kinds of things in dig_port->hdcp_port_data. This looks rather
broken to me.

So has anyone actually thought what happens if you first use
MST on the port, and then later switch to SST on the same port?

-- 
Ville Syrjälä
Intel

Re: [Intel-gfx] i915 MST HDCP code looks broken

[Gupta, Anshuman]

> -----Original Message-----
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Sent: Monday, October 4, 2021 4:22 PM
> To: intel-gfx@lists.freedesktop.org
> Cc: Sean Paul <seanpaul@chromium.org>; Gupta, Anshuman
> <anshuman.gupta@intel.com>; C, Ramalingam <ramalingam.c@intel.com>; B S,
> Karthik <karthik.b.s@intel.com>
> Subject: i915 MST HDCP code looks broken
> 
> Hi,
> 
> I took a quick peek at intel_dp_add_mst_connector() the other day and noticed
> that it calls intel_dp_hdcp_init() and passes in the SST dig_port. And digging in a
> bit further that seems to clobber all kinds of things in dig_port->hdcp_port_data.
> This looks rather broken to me.
> 
> So has anyone actually thought what happens if you first use MST on the port,
> and then later switch to SST on the same port?
AFAIU there shouldn't be , when the last connector of MST topology get destroyed  and it switches to SST mode on same port.
The base static connector of same dig_port should get connected and will call  intel_dp_init_connector()->intel_dp_hdcp_init().
What is the specific sequence is broken here , is it the connector destroy path ? 
> --
> Ville Syrjälä
> Intel

Re: [Intel-gfx] i915 MST HDCP code looks broken

[Ville Syrjälä]

On Mon, Oct 04, 2021 at 03:04:01PM +0000, Gupta, Anshuman wrote:
> 
> 
> > -----Original Message-----
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Sent: Monday, October 4, 2021 4:22 PM
> > To: intel-gfx@lists.freedesktop.org
> > Cc: Sean Paul <seanpaul@chromium.org>; Gupta, Anshuman
> > <anshuman.gupta@intel.com>; C, Ramalingam <ramalingam.c@intel.com>; B S,
> > Karthik <karthik.b.s@intel.com>
> > Subject: i915 MST HDCP code looks broken
> > 
> > Hi,
> > 
> > I took a quick peek at intel_dp_add_mst_connector() the other day and noticed
> > that it calls intel_dp_hdcp_init() and passes in the SST dig_port. And digging in a
> > bit further that seems to clobber all kinds of things in dig_port->hdcp_port_data.
> > This looks rather broken to me.
> > 
> > So has anyone actually thought what happens if you first use MST on the port,
> > and then later switch to SST on the same port?
> AFAIU there shouldn't be , when the last connector of MST topology get destroyed  and it switches to SST mode on same port.
> The base static connector of same dig_port should get connected and will call  intel_dp_init_connector()->intel_dp_hdcp_init().

SST conectors are static. They are created exactly once when the driver
loads.

-- 
Ville Syrjälä
Intel