[PATCH v3 05/12] usb: typec: tcpm: process receive and transmission of sop' messages

RD Babiera
2024-01-08T19:16:39Z

Add negotiated revision and tx/rx message ids to tcpm_port specific to
SOP'. tx_sop_type is added to the tcpm_port to determine whether the
current constructed message will be sent over SOP or SOP' if not
sent immediately.

tcpm_pd_rx_handler updates the received message ids. SOP* messages are not
processed afterwards. The handler also calls tcpm_can_communicate_sop_prime
to determine if a SOP' message is directed towards the port, and drops SOP'
messages it should not respond to.

tcpm_can_communicate_sop_prime is added as a helper to determine whether
the port is capable of communicating over SOP' at a given moment. Being
the Vconn source is a requirement in Power Delivery 3.0 but only a
recommendation in Power Delviery 2.0. Because the port should ensure that
the cable is powered before communication, always enforce the port is the
Vconn source regardless of revision.

Signed-off-by: RD Babiera <rdbabiera@google.com>
---
Changes since v2:
* Fixed style errors, switch statements with TCPC_TX_SOP now combine
with default case.
---
drivers/usb/typec/tcpm/tcpm.c | 145 +++++++++++++++++++++++++++++++---
1 file changed, 134 insertions(+), 11 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index ff0fcf560c88..d2ca85c8fec6 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -505,6 +505,35 @@ struct tcpm_port {
* transitions.
*/
bool potential_contaminant;
+
+ /* SOP* Related Fields */
+ /*
+ * tx_sop_type determines which SOP* a message is being sent on.
+ * For messages that are queued and not sent immediately such as in
+ * tcpm_queue_message or messages that send after state changes,
+ * the tx_sop_type is set accordingly.
+ */
+ enum tcpm_transmit_type tx_sop_type;
+ /*
+ * Prior to discovering the port partner's Specification Revision, the
+ * Vconn source and cable plug will use the lower of their two revisions.
+ *
+ * When the port partner's Specification Revision is discovered, the following
+ * rules are put in place.
+ * 1. If the cable revision (1) is lower than the revision negotiated
+ * between the port and partner (2), the port and partner will communicate
+ * on revision (2), but the port and cable will communicate on revision (1).
+ * 2. If the cable revision (1) is higher than the revision negotiated
+ * between the port and partner (2), the port and partner will communicate
+ * on revision (2), and the port and cable will communicate on revision (2)
+ * as well.
+ */
+ unsigned int negotiated_rev_prime;
+ /*
+ * Each SOP* type must maintain their own tx and rx message IDs
+ */
+ unsigned int message_id_prime;
+ unsigned int rx_msgid_prime;
#ifdef CONFIG_DEBUG_FS
struct dentry *dentry;
struct mutex logbuffer_lock; /* log buffer access lock */
@@ -894,19 +923,30 @@ static void tcpm_ams_finish(struct tcpm_port *port)
}

static int tcpm_pd_transmit(struct tcpm_port *port,
- enum tcpm_transmit_type type,
+ enum tcpm_transmit_type tx_sop_type,
const struct pd_message *msg)
{
unsigned long timeout;
int ret;
+ unsigned int negotiated_rev;
+
+ switch (tx_sop_type) {
+ case TCPC_TX_SOP_PRIME:
+ negotiated_rev = port->negotiated_rev_prime;
+ break;
+ case TCPC_TX_SOP:
+ default:
+ negotiated_rev = port->negotiated_rev;
+ break;
+ }

if (msg)
tcpm_log(port, "PD TX, header: %#x", le16_to_cpu(msg->header));
else
- tcpm_log(port, "PD TX, type: %#x", type);
+ tcpm_log(port, "PD TX, type: %#x", tx_sop_type);

reinit_completion(&port->tx_complete);
- ret = port->tcpc->pd_transmit(port->tcpc, type, msg, port->negotiated_rev);
+ ret = port->tcpc->pd_transmit(port->tcpc, tx_sop_type, msg, negotiated_rev);
if (ret < 0)
return ret;

@@ -919,7 +959,17 @@ static int tcpm_pd_transmit(struct tcpm_port *port,

switch (port->tx_status) {
case TCPC_TX_SUCCESS:
- port->message_id = (port->message_id + 1) & PD_HEADER_ID_MASK;
+ switch (tx_sop_type) {
+ case TCPC_TX_SOP_PRIME:
+ port->message_id_prime = (port->message_id_prime + 1) &
+ PD_HEADER_ID_MASK;
+ break;
+ case TCPC_TX_SOP:
+ default:
+ port->message_id = (port->message_id + 1) &
+ PD_HEADER_ID_MASK;
+ break;
+ }
/*
* USB PD rev 2.0, 8.3.2.2.1:
* USB PD rev 3.0, 8.3.2.1.3:
@@ -1604,6 +1654,57 @@ static void tcpm_register_partner_altmodes(struct tcpm_port *port)

#define supports_modal(port) PD_IDH_MODAL_SUPP((port)->partner_ident.id_header)

+/*
+ * Helper to determine whether the port is capable of SOP' communication at the
+ * current point in time.
+ */
+static bool tcpm_can_communicate_sop_prime(struct tcpm_port *port)
+{
+ /* Check to see if tcpc supports SOP' communication */
+ if (!port->tcpc->cable_comm_capable || !port->tcpc->cable_comm_capable(port->tcpc))
+ return false;
+ /*
+ * Power Delivery 2.0 Section 6.3.11
+ * Before communicating with a Cable Plug a Port Should ensure that it
+ * is the Vconn Source and that the Cable Plugs are powered by
+ * performing a Vconn swap if necessary. Since it cannot be guaranteed
+ * that the present Vconn Source is supplying Vconn, the only means to
+ * ensure that the Cable Plugs are powered is for a Port wishing to
+ * communicate with a Cable Plug is to become the Vconn Source.
+ *
+ * Power Delivery 3.0 Section 6.3.11
+ * Before communicating with a Cable Plug a Port Shall ensure that it
+ * is the Vconn source.
+ */
+ if (port->vconn_role != TYPEC_SOURCE)
+ return false;
+ /*
+ * Power Delivery 2.0 Section 2.4.4
+ * When no Contract or an Implicit Contract is in place the Source can
+ * communicate with a Cable Plug using SOP' packets in order to discover
+ * its characteristics.
+ *
+ * Power Delivery 3.0 Section 2.4.4
+ * When no Contract or an Implicit Contract is in place only the Source
+ * port that is supplying Vconn is allowed to send packets to a Cable
+ * Plug and is allowed to respond to packets from the Cable Plug.
+ */
+ if (!port->explicit_contract)
+ return port->pwr_role == TYPEC_SOURCE;
+ if (port->negotiated_rev == PD_REV30)
+ return true;
+ /*
+ * Power Delivery 2.0 Section 2.4.4
+ *
+ * When an Explicit Contract is in place the DFP (either the Source or
+ * the Sink) can communicate with the Cable Plug(s) using SOP’/SOP”
+ * Packets (see Figure 2-3).
+ */
+ if (port->negotiated_rev == PD_REV20)
+ return port->data_role == TYPEC_HOST;
+ return false;
+}
+
static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
const u32 *p, int cnt, u32 *response,
enum adev_actions *adev_action)
@@ -2989,14 +3090,18 @@ static void tcpm_pd_rx_handler(struct kthread_work *work)
tcpm_log(port, "PD RX, header: %#x [%d]", le16_to_cpu(msg->header),
port->attached);

- /* Ignore SOP' for now */
- if (rx_sop_type == TCPC_TX_SOP_PRIME)
- goto done;
-
if (port->attached) {
enum pd_ctrl_msg_type type = pd_header_type_le(msg->header);
unsigned int msgid = pd_header_msgid_le(msg->header);

+ /*
+ * Drop SOP' messages if cannot receive via
+ * tcpm_can_communicate_sop_prime
+ */
+ if (rx_sop_type == TCPC_TX_SOP_PRIME &&
+ !tcpm_can_communicate_sop_prime(port))
+ goto done;
+
/*
* USB PD standard, 6.6.1.2:
* "... if MessageID value in a received Message is the
@@ -3006,16 +3111,27 @@ static void tcpm_pd_rx_handler(struct kthread_work *work)
* Message). Note: this shall not apply to the Soft_Reset
* Message which always has a MessageID value of zero."
*/
- if (msgid == port->rx_msgid && type != PD_CTRL_SOFT_RESET)
+ switch (rx_sop_type) {
+ case TCPC_TX_SOP_PRIME:
+ if (msgid == port->rx_msgid_prime)
+ goto done;
+ port->rx_msgid_prime = msgid;
+ /* Ignore SOP' for now */
goto done;
- port->rx_msgid = msgid;
+ case TCPC_TX_SOP:
+ default:
+ if (msgid == port->rx_msgid && type != PD_CTRL_SOFT_RESET)
+ goto done;
+ port->rx_msgid = msgid;
+ break;
+ }

/*
* If both ends believe to be DFP/host, we have a data role
* mismatch.
*/
if (!!(le16_to_cpu(msg->header) & PD_HEADER_DATA_ROLE) ==
- (port->data_role == TYPEC_HOST)) {
+ (port->data_role == TYPEC_HOST) && rx_sop_type == TCPC_TX_SOP) {
tcpm_log(port,
"Data role mismatch, initiating error recovery");
tcpm_set_state(port, ERROR_RECOVERY, 0);
@@ -3720,6 +3836,7 @@ static void tcpm_reset_port(struct tcpm_port *port)
* we can check tcpm_pd_rx_handler() if we had seen it before.
*/
port->rx_msgid = -1;
+ port->rx_msgid_prime = -1;

port->tcpc->set_pd_rx(port->tcpc, false);
tcpm_init_vbus(port); /* also disables charging */
@@ -4034,8 +4151,11 @@ static void run_state_machine(struct tcpm_port *port)
port->pwr_opmode = TYPEC_PWR_MODE_USB;
port->caps_count = 0;
port->negotiated_rev = PD_MAX_REV;
+ port->negotiated_rev_prime = PD_MAX_REV;
port->message_id = 0;
+ port->message_id_prime = 0;
port->rx_msgid = -1;
+ port->rx_msgid_prime = -1;
port->explicit_contract = false;
/* SNK -> SRC POWER/FAST_ROLE_SWAP finished */
if (port->ams == POWER_ROLE_SWAP ||
@@ -4275,8 +4395,11 @@ static void run_state_machine(struct tcpm_port *port)
typec_set_pwr_opmode(port->typec_port, opmode);
port->pwr_opmode = TYPEC_PWR_MODE_USB;
port->negotiated_rev = PD_MAX_REV;
+ port->negotiated_rev_prime = PD_MAX_REV;
port->message_id = 0;
+ port->message_id_prime = 0;
port->rx_msgid = -1;
+ port->rx_msgid_prime = -1;
port->explicit_contract = false;

if (port->ams == POWER_ROLE_SWAP ||
--
2.43.0.472.g3155946c3a-goog