Atm HPD disconnect events on TypeC ports will break things, since we'll
switch the TypeC mode (between legacy and disconnected modes as well as
among USB DP alternate, Thunderbolt alternate and disconnected modes) on
the fly from the HPD disconnect interrupt work while the port may be
still active.

Even if the port happens to be not active during the disconnect we'd
still have a problem during a subsequent modeset or AUX transfer that
could happen regardless of the port's connected state. For instance the
system resume display mode restore code and userspace could perform a
modeset on the port or userspace could start an AUX transfer even if the
port is in disconnected state.

To fix this keep TypeC legacy ports in legacy mode whenever we're not
suspended. This mode is a static configuration as opposed to the
Thunderbolt and USB DP alternate modes between which we can switch
dynamically.

We determine if a TypeC port is legacy (wired to a legacy HDMI or a
legacy DP connector) via the VBT DDI port specific USB-TypeC and
Thunderbolt flags. If both these flags are cleared then the port is
configured for legacy mode.

On such legacy ports we'll run the TypeC PHY connect sequence explicitly
during driver loading and system resume (vs. running the sequence during
HPD processing). The connect will succeed even if the display is not
connected to begin with (or disappears during the suspended state) since
for legacy ports the PORT_TX_DFLEXDPPMS / DP_PHY_MODE_STATUS_COMPLETED
flag is always set (as opposed to the USB DP alternate mode where it
gets set only when a display is connected).

Correspondingly run the TypeC PHY disconnect sequence during system
suspend and driver unloading. For the unloading case I had to split
up intel_dp_encoder_destroy() to be able to have the 1. flush any
pending encoder work, 2. disconnect TC PHY, 3. call DRM core cleanup and
kfree on the encoder object.

For now run the PHY disconnect during suspend only for TypeC legacy
ports. We will need to disconnect even in USB DP alternate mode in the
future, but atm we don't have a way to reconnect the port in this mode
during resume if the display disappears while being suspended. So for
now punt on this case.

Note that we do not disconnect the port during runtime suspend; in
legacy mode there are no shared HW resources (PHY lanes) with other HW
blocks (USB), so no need to release / reacquire these resources as with
USB DP alternate mode. The only reason to disconnect legacy ports during
system suspend is that the PORT_TX_DFLEXDPPMS /
DP_PHY_MODE_STATUS_COMPLETED flag must be rechecked and the port must be
connected again during system resume. We'll also have to turn the check
for this flag into a poll, after figuring out what's the proper timeout
value for it.

v2:
- Remove the redundant special casing of legacy mode when doing a
  disconnect in icl_tc_port_connected(). It's guaranteed already that we
  won't disconnect legacy ports in that function.
- Add a note about the new intel_ddi_encoder_destroy() hook.
- Reword the commit message after switching to the VBT based detection.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108070
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108924
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181214182703.18865-4-imre.deak@intel.com