[PATCH 0/5] usb: typec: cable comms on RT1711H-compatible TCPCs and FUSB302

[Alexey Charkov]

Neither the RT1711H family (including the HUSB311 and ET7304) nor the
FUSB302 lets TCPM talk to cable plugs today, so cable discovery is
skipped, and with it the cable's current and speed ratings.

The RT1711H family handles SOP' like any other TCPCI-compliant TCPC, but
enabling it exposed a problem in the TCPCI core: it set SOP' in
RECEIVE_DETECT whenever the TCPC can talk to cables, regardless of who
sources VCONN. With the partner as the VCONN Source, the port then acks
and processes the partner's own traffic with the cable plug.

Patch 1 fixes a TCPM bug that cable communication on the FUSB302 made
visible: after a VCONN swap, a source resets the cable plug twice.
Patch 2 lets a TCPCI TCPC receive SOP' only while it sources VCONN,
which also affects the Maxim TCPCs, the only ones that enable SOP'
today. Patch 3 enables SOP' on the RT1711H family. Patches 4 and 5 add
SOP' to the FUSB302 driver, receiving it under the same VCONN rule.

Tested on an RK3576 EVB1 (HUSB311, source-only) and Flipper One boards
(FUSB302B):
- Without patch 2, a FUSB302 sink sent SOP' Discover Identity over a
  cable with no e-marker, so the HUSB311 had no VCONN to source. The
  HUSB311 acked each one and its TCPM answered over SOP, after which the
  sink soft reset the contract every time.
- With patch 2, the same messages went unacked and the HUSB311 port
  correctly ignored them.
- Over an e-marked 5A EPR cable, the HUSB311 sourced VCONN, read the
  cable identity and completed discovery, while the FUSB302 sink kept
  SOP' reception off.
- With a FUSB302 as source on the same cable, it sourced VCONN, read
  the cable identity and completed discovery. The cable plug accepted
  the FUSB302's automatic GoodCRC to its replies, which the datasheet
  leaves undocumented for SOP'.
- Between two FUSB302 ports on the same cable, VCONN swaps both ways
  moved SOP' reception along with VCONN, and each new VCONN Source
  soft reset the cable plug over SOP'. Without patch 1, the source did
  so twice.

Signed-off-by: Alexey Charkov <alchark@xxxxxxxxxxx>
---
Alexey Charkov (5):
      usb: typec: tcpm: Stop a source from repeating a cable Soft_Reset
      usb: typec: tcpci: Receive SOP' only while sourcing VCONN
      usb: typec: tcpci_rt1711h: Enable SOP' communication
      usb: typec: fusb302: Tell SOP' messages apart from SOP
      usb: typec: fusb302: Enable SOP' communication

 drivers/usb/typec/tcpm/fusb302.c       | 63 ++++++++++++++++++++++++++---
 drivers/usb/typec/tcpm/fusb302_reg.h   | 10 +++++
 drivers/usb/typec/tcpm/tcpci.c         | 72 +++++++++++++++++++++++-----------
 drivers/usb/typec/tcpm/tcpci_rt1711h.c |  1 +
 drivers/usb/typec/tcpm/tcpm.c          |  2 +
 5 files changed, 119 insertions(+), 29 deletions(-)
---
base-commit: 2637bdec0535a2044cd830eba9a79363651d9043
change-id: 20261103-husb311-cable-comm-46f2e77e4c18

Best regards,
--  
Alexey Charkov <alchark@xxxxxxxxxxx>