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

Heikki Krogerus
2024-01-15T09:14:04Z

On Mon, Jan 08, 2024 at 07:16:18PM +0000, RD Babiera wrote:
> 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>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.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

--
heikki