Re: [PATCH] usb: typec: tcpm: collision avoidance

From: Guenter Roeck
Date: Tue Mar 19 2019 - 13:38:09 EST

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In reply to: Kyle Tso: "[PATCH] usb: typec: tcpm: collision avoidance"
Next in thread: Kyle Tso: "Re: [PATCH] usb: typec: tcpm: collision avoidance"
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> This patch provides the implementation of Collision Avoidance introduced
> in PD3.0. The start of each Atomic Message Sequence (AMS) initiated by
> the port will be denied if the current AMS is not interruptible. The
> Source port will set the CC to SinkTxNG if it is going to initiate an
> AMS, and SinkTxOk otherwise. Meanwhile, any AMS initiated by a Sink port
> will be denied in TCPM if the port partner (Source) sets SinkTxNG except
> for HARD_RESET and SOFT_RESET.
>

That wil require a detailed review; I am quite concerned that the added
complexity may have negative impact on existing (and possibly less than
perfect partners.

Coupld of initial comments below.

Guenter

> Signed-off-by: Kyle Tso <kyletso@xxxxxxxxxx>
> ---
> drivers/usb/typec/tcpm/tcpm.c | 539 ++++++++++++++++++++++++++++++----
> include/linux/usb/pd.h | 1 +
> include/linux/usb/tcpm.h | 4 +
> 3 files changed, 484 insertions(+), 60 deletions(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 0f62db091d8d..312008cdc7d3 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -71,6 +71,8 @@
> S(SNK_HARD_RESET_SINK_ON), \
> \
> S(SOFT_RESET), \
> + S(SRC_SOFT_RESET_WAIT_SNK_TX), \
> + S(SNK_SOFT_RESET), \
> S(SOFT_RESET_SEND), \
> \
> S(DR_SWAP_ACCEPT), \
> @@ -124,7 +126,45 @@
> \
> S(ERROR_RECOVERY), \
> S(PORT_RESET), \
> - S(PORT_RESET_WAIT_OFF)
> + S(PORT_RESET_WAIT_OFF), \
> + \
> + S(AMS_START)
> +
> +#define FOREACH_AMS(S) \
> + S(NONE_AMS), \
> + S(POWER_NEGOTIATION), \
> + S(GOTOMIN), \
> + S(SOFT_RESET_AMS), \
> + S(HARD_RESET), \
> + S(CABLE_RESET), \
> + S(GET_SOURCE_CAPABILITIES), \
> + S(GET_SINK_CAPABILITIES), \
> + S(POWER_ROLE_SWAP), \
> + S(FAST_ROLE_SWAP), \
> + S(DATA_ROLE_SWAP), \
> + S(VCONN_SWAP), \
> + S(SOURCE_ALERT), \
> + S(GETTING_SOURCE_EXTENDED_CAPABILITIES),\
> + S(GETTING_SOURCE_SINK_STATUS), \
> + S(GETTING_BATTERY_CAPABILITIES), \
> + S(GETTING_BATTERY_STATUS), \
> + S(GETTING_MANUFACTURER_INFORMATION), \
> + S(SECURITY), \
> + S(FIRMWARE_UPDATE), \
> + S(DISCOVER_IDENTITY), \
> + S(SOURCE_STARTUP_CABLE_PLUG_DISCOVER_IDENTITY), \
> + S(DISCOVER_SVIDS), \
> + S(DISCOVER_MODES), \
> + S(DFP_TO_UFP_ENTER_MODE), \
> + S(DFP_TO_UFP_EXIT_MODE), \
> + S(DFP_TO_CABLE_PLUG_ENTER_MODE), \
> + S(DFP_TO_CABLE_PLUG_EXIT_MODE), \
> + S(ATTENTION), \
> + S(BIST), \
> + S(UNSTRUCTURED_VDMS), \
> + S(STRUCTURED_VDMS), \
> + S(COUNTRY_INFO), \
> + S(COUNTRY_CODES)
>
> #define GENERATE_ENUM(e) e
> #define GENERATE_STRING(s) #s
> @@ -137,6 +177,14 @@ static const char * const tcpm_states[] = {
> FOREACH_STATE(GENERATE_STRING)
> };
>
> +enum tcpm_ams {
> + FOREACH_AMS(GENERATE_ENUM)
> +};
> +
> +static const char * const tcpm_ams_str[] = {
> + FOREACH_AMS(GENERATE_STRING)
> +};
> +
> enum vdm_states {
> VDM_STATE_ERR_BUSY = -3,
> VDM_STATE_ERR_SEND = -2,
> @@ -146,6 +194,7 @@ enum vdm_states {
> VDM_STATE_READY = 1,
> VDM_STATE_BUSY = 2,
> VDM_STATE_WAIT_RSP_BUSY = 3,
> + VDM_STATE_SEND_MESSAGE = 4,
> };
>
> enum pd_msg_request {
> @@ -320,6 +369,11 @@ struct tcpm_port {
> /* port belongs to a self powered device */
> bool self_powered;
>
> + /* Collision Avoidance and Atomic Message Sequence */
> + enum tcpm_state upcoming_state;
> + enum tcpm_ams ams;
> + bool in_ams;
> +
> #ifdef CONFIG_DEBUG_FS
> struct dentry *dentry;
> struct mutex logbuffer_lock; /* log buffer access lock */
> @@ -371,6 +425,16 @@ struct pd_rx_event {
> ((port)->try_src_count == 0 && (port)->try_role == TYPEC_SOURCE && \
> (port)->port_type == TYPEC_PORT_DRP)
>
> +#define tcpm_sink_tx_ok(port) \
> + (tcpm_port_is_sink(port) && \
> + ((port)->cc1 == TYPEC_CC_RP_3_0 || (port)->cc2 == TYPEC_CC_RP_3_0))
> +
> +#define tcpm_switch_state(port, state, delay) \
> + do { \
> + (port)->upcoming_state = INVALID_STATE; \
> + tcpm_set_state(port, state, delay); \
> + } while (0)
> +
> static enum tcpm_state tcpm_default_state(struct tcpm_port *port)
> {
> if (port->port_type == TYPEC_PORT_DRP) {
> @@ -600,6 +664,9 @@ static void tcpm_debugfs_exit(const struct tcpm_port *port) { }
>
> #endif
>
> +static int tcpm_ams_start(struct tcpm_port *port, enum tcpm_ams ams,
> + bool start);
> +

Does this have to be a forward declaration ?

> static int tcpm_pd_transmit(struct tcpm_port *port,
> enum tcpm_transmit_type type,
> const struct pd_message *msg)
> @@ -627,13 +694,30 @@ 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;
> - return 0;
> + /*
> + * USB PD rev 3.0, 8.3.2.1.3:
> + * "... Note that every AMS is Interruptible until the first
> + * Message in the sequence has been successfully sent (GoodCRC
> + * Message received)."
> + */
> + if ((port->negotiated_rev >= PD_REV30) &&
> + (port->ams != NONE_AMS))

Excessive ( )

> + port->in_ams = true;
> + break;
> case TCPC_TX_DISCARDED:
> - return -EAGAIN;
> + ret = -EAGAIN;
> + break;
> case TCPC_TX_FAILED:
> default:
> - return -EIO;
> + ret = -EIO;
> + break;
> }
> +
> + /* Some AMS don't expect responses. Finish them here. */
> + if (port->ams == ATTENTION || port->ams == SOURCE_ALERT)
> + tcpm_ams_start(port, port->ams, false);

Calling tcpm_ams_start() when the actual action is finish, and even more
so when the code itself has almost no overlap, doesn't make sense to me.
This should be a call to a separate function. More on that below.

> +
> + return ret;
> }
>
> void tcpm_pd_transmit_complete(struct tcpm_port *port,
> @@ -883,17 +967,20 @@ static void tcpm_set_state(struct tcpm_port *port, enum tcpm_state state,
> unsigned int delay_ms)
> {
> if (delay_ms) {
> - tcpm_log(port, "pending state change %s -> %s @ %u ms",
> - tcpm_states[port->state], tcpm_states[state],
> - delay_ms);
> + tcpm_log(port, "pending state change %s -> %s @ %u ms [%s]",
> + tcpm_states[port->state], tcpm_states[state], delay_ms,
> + port->negotiated_rev >= PD_REV30 ?
> + tcpm_ams_str[port->ams] : "");

"[%s]" results in [] for PD 2.0. This is undesirable and confusing.
[] should be part of the conditional string. Also, The potential text
in [] doesn't have an explanation.

port->negotiated_rev >= PD_REV30 ?
tcpm_ams_str[port->ams] : "");

is repeated several times and should be a separate function or macro.

> port->delayed_state = state;
> mod_delayed_work(port->wq, &port->state_machine,
> msecs_to_jiffies(delay_ms));
> port->delayed_runtime = jiffies + msecs_to_jiffies(delay_ms);
> port->delay_ms = delay_ms;
> } else {
> - tcpm_log(port, "state change %s -> %s",
> - tcpm_states[port->state], tcpm_states[state]);
> + tcpm_log(port, "state change %s -> %s [%s]",
> + tcpm_states[port->state], tcpm_states[state],
> + port->negotiated_rev >= PD_REV30 ?
> + tcpm_ams_str[port->ams] : "");
> port->delayed_state = INVALID_STATE;
> port->prev_state = port->state;
> port->state = state;
> @@ -915,10 +1002,12 @@ static void tcpm_set_state_cond(struct tcpm_port *port, enum tcpm_state state,
> tcpm_set_state(port, state, delay_ms);
> else
> tcpm_log(port,
> - "skipped %sstate change %s -> %s [%u ms], context state %s",
> + "skipped %sstate change %s -> %s [%u ms], context state %s [%s]",
> delay_ms ? "delayed " : "",
> tcpm_states[port->state], tcpm_states[state],
> - delay_ms, tcpm_states[port->enter_state]);
> + delay_ms, tcpm_states[port->enter_state],
> + port->negotiated_rev >= PD_REV30 ?
> + tcpm_ams_str[port->ams] : "");
> }
>
> static void tcpm_queue_message(struct tcpm_port *port,
> @@ -928,6 +1017,160 @@ static void tcpm_queue_message(struct tcpm_port *port,
> mod_delayed_work(port->wq, &port->state_machine, 0);
> }
>
> +static void tcpm_set_cc(struct tcpm_port *port, enum typec_cc_status cc)
> +{
> + tcpm_log(port, "cc:=%d", cc);
> + port->cc_req = cc;
> + port->tcpc->set_cc(port->tcpc, cc);
> +}
> +
> +static bool tcpm_vdm_ams(struct tcpm_port *port)
> +{
> + switch (port->ams) {
> + case DISCOVER_IDENTITY:
> + case SOURCE_STARTUP_CABLE_PLUG_DISCOVER_IDENTITY:
> + case DISCOVER_SVIDS:
> + case DISCOVER_MODES:
> + case DFP_TO_UFP_ENTER_MODE:
> + case DFP_TO_UFP_EXIT_MODE:
> + case DFP_TO_CABLE_PLUG_ENTER_MODE:
> + case DFP_TO_CABLE_PLUG_EXIT_MODE:
> + case ATTENTION:
> + case UNSTRUCTURED_VDMS:
> + case STRUCTURED_VDMS:
> + break;
> + default:
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static bool tcpm_ams_interruptible(struct tcpm_port *port)
> +{
> + switch (port->ams) {
> + /* Interruptible AMS */
> + case NONE_AMS:
> + case SECURITY:
> + case FIRMWARE_UPDATE:
> + case DISCOVER_IDENTITY:
> + case SOURCE_STARTUP_CABLE_PLUG_DISCOVER_IDENTITY:
> + case DISCOVER_SVIDS:
> + case DISCOVER_MODES:
> + case DFP_TO_UFP_ENTER_MODE:
> + case DFP_TO_UFP_EXIT_MODE:
> + case DFP_TO_CABLE_PLUG_ENTER_MODE:
> + case DFP_TO_CABLE_PLUG_EXIT_MODE:
> + case UNSTRUCTURED_VDMS:
> + case STRUCTURED_VDMS:
> + case COUNTRY_INFO:
> + case COUNTRY_CODES:
> + break;
> + /* Non-Interruptible AMS */
> + default:
> + if (port->in_ams)
> + return false;
> + break;
> + }
> +
> + return true;
> +}
> +
> +static int tcpm_ams_start(struct tcpm_port *port, enum tcpm_ams ams, bool start)
> +{
> + int ret = 0;
> +
> + if (port->negotiated_rev < PD_REV30) {
> + port->upcoming_state = INVALID_STATE;
> + return -EOPNOTSUPP;
> + }
> +
> + if (!start)
> + goto ams_finish;

This is just confusing. Please handle "finish" in a separate function.
Checking the PD version is not enough overlap to warrant this kind of code.

This is even more true since every call of tcpm_ams_start(port, ams, false)
actually has port->ams as second parameter. This makes the code even more
complex and more difficult to understand than it already is.

> +
> + tcpm_log(port, "AMS: %s start", tcpm_ams_str[ams]);
> +
> + if (!tcpm_ams_interruptible(port) && ams != HARD_RESET) {
> + port->upcoming_state = INVALID_STATE;
> + tcpm_log(port, "AMS: %s not interruptible, aborting",
> + tcpm_ams_str[port->ams]);
> + return -EAGAIN;
> + }
> +
> + if (port->pwr_role == TYPEC_SOURCE) {
> + enum typec_cc_status cc_req;
> +
> + port->ams = ams;
> +
> + if (ams == HARD_RESET) {
> + tcpm_set_cc(port, tcpm_rp_cc(port));
> + tcpm_pd_transmit(port, TCPC_TX_HARD_RESET, NULL);
> + tcpm_set_state(port, HARD_RESET_START, 0);
> + return 0;
> + } else if (ams == SOFT_RESET_AMS) {
> + if (!port->explicit_contract) {
> + port->upcoming_state = INVALID_STATE;
> + tcpm_set_cc(port, tcpm_rp_cc(port));
> + return 0;
> + }
> + } else if (tcpm_vdm_ams(port)) {
> + /* tSinkTx is enforced in vdm_run_state_machine */
> + tcpm_set_cc(port, SINK_TX_NG);
> + return 0;
> + }
> +
> + cc_req = port->cc_req;
> + tcpm_set_cc(port, SINK_TX_NG);
> + if (port->state == SRC_READY ||
> + port->state == SRC_STARTUP ||
> + port->state == SRC_SOFT_RESET_WAIT_SNK_TX ||
> + port->state == SOFT_RESET ||
> + port->state == SOFT_RESET_SEND)
> + tcpm_set_state(port, AMS_START, cc_req == SINK_TX_OK ?
> + PD_T_SINK_TX : 0);
> + else
> + tcpm_set_state(port, SRC_READY, cc_req == SINK_TX_OK ?
> + PD_T_SINK_TX : 0);
> + } else {
> + if (!tcpm_sink_tx_ok(port) &&
> + ams != SOFT_RESET_AMS &&
> + ams != HARD_RESET) {
> + port->upcoming_state = INVALID_STATE;
> + tcpm_log(port, "Sink TX No Go");
> + return -EAGAIN;
> + }
> +
> + port->ams = ams;
> +
> + if (ams == HARD_RESET) {
> + tcpm_pd_transmit(port, TCPC_TX_HARD_RESET, NULL);
> + tcpm_set_state(port, HARD_RESET_START, 0);
> + return 0;
> + } else if (tcpm_vdm_ams(port)) {
> + return 0;
> + }
> +
> + if (port->state == SNK_READY ||
> + port->state == SNK_SOFT_RESET)
> + tcpm_set_state(port, AMS_START, 0);
> + else
> + tcpm_set_state(port, SNK_READY, 0);
> + }
> +
> + return ret;
> +
> +ams_finish:
> + tcpm_log(port, "AMS: %s finished", tcpm_ams_str[ams]);
> +
> + if (port->pwr_role == TYPEC_SOURCE)
> + tcpm_set_cc(port, SINK_TX_OK);
> +
> + port->in_ams = false;
> + port->ams = NONE_AMS;
> +
> + return ret;
> +}
> +
> /*
> * VDM/VDO handling functions
> */
> @@ -1164,6 +1407,7 @@ static int tcpm_pd_svdm(struct tcpm_port *port, const __le32 *payload, int cnt,
> default:
> break;
> }
> + tcpm_ams_start(port, port->ams, false);
> break;
> case CMDT_RSP_NAK:
> switch (cmd) {
> @@ -1175,6 +1419,7 @@ static int tcpm_pd_svdm(struct tcpm_port *port, const __le32 *payload, int cnt,
> default:
> break;
> }
> + tcpm_ams_start(port, port->ams, false);
> break;
> default:
> break;
> @@ -1260,7 +1505,7 @@ static unsigned int vdm_ready_timeout(u32 vdm_hdr)
> static void vdm_run_state_machine(struct tcpm_port *port)
> {
> struct pd_message msg;
> - int i, res;
> + int i, res = 0;
>
> switch (port->vdm_state) {
> case VDM_STATE_READY:
> @@ -1277,27 +1522,47 @@ static void vdm_run_state_machine(struct tcpm_port *port)
> if (port->state != SRC_READY && port->state != SNK_READY)
> break;
>
> - /* Prepare and send VDM */
> - memset(&msg, 0, sizeof(msg));
> - msg.header = PD_HEADER_LE(PD_DATA_VENDOR_DEF,
> - port->pwr_role,
> - port->data_role,
> - port->negotiated_rev,
> - port->message_id, port->vdo_count);
> - for (i = 0; i < port->vdo_count; i++)
> - msg.payload[i] = cpu_to_le32(port->vdo_data[i]);
> - res = tcpm_pd_transmit(port, TCPC_TX_SOP, &msg);
> - if (res < 0) {
> - port->vdm_state = VDM_STATE_ERR_SEND;
> - } else {
> - unsigned long timeout;
> + if (PD_VDO_CMDT(port->vdo_data[0]) == CMDT_INIT) {
> + switch (PD_VDO_CMD(port->vdo_data[0])) {
> + case CMD_DISCOVER_IDENT:
> + res = tcpm_ams_start(port, DISCOVER_IDENTITY,
> + true);
> + break;
> + case CMD_DISCOVER_SVID:
> + res = tcpm_ams_start(port, DISCOVER_SVIDS,
> + true);
> + break;
> + case CMD_DISCOVER_MODES:
> + res = tcpm_ams_start(port, DISCOVER_MODES,
> + true);
> + break;
> + case CMD_ENTER_MODE:
> + res = tcpm_ams_start(port,
> + DFP_TO_UFP_ENTER_MODE,
> + true);
> + break;
> + case CMD_EXIT_MODE:
> + res = tcpm_ams_start(port, DFP_TO_UFP_EXIT_MODE,
> + true);
> + break;
> + case CMD_ATTENTION:
> + res = tcpm_ams_start(port, ATTENTION, true);
> + break;
> + default:
> + res = -EOPNOTSUPP;
> + break;
> + }
>
> - port->vdm_retries = 0;
> - port->vdm_state = VDM_STATE_BUSY;
> - timeout = vdm_ready_timeout(port->vdo_data[0]);
> - mod_delayed_work(port->wq, &port->vdm_state_machine,
> - timeout);
> + if (res == -EAGAIN)
> + return;
> }
> +
> + port->vdm_state = VDM_STATE_SEND_MESSAGE;
> + mod_delayed_work(port->wq, &port->vdm_state_machine,
> + (res != -EOPNOTSUPP) &&
> + (port->pwr_role == TYPEC_SOURCE) &&
> + (PD_VDO_CMDT(port->vdo_data[0]) == CMDT_INIT) ?
> + PD_T_SINK_TX : 0);
> break;
> case VDM_STATE_WAIT_RSP_BUSY:
> port->vdo_data[0] = port->vdo_retry;
> @@ -1306,6 +1571,8 @@ static void vdm_run_state_machine(struct tcpm_port *port)
> break;
> case VDM_STATE_BUSY:
> port->vdm_state = VDM_STATE_ERR_TMOUT;
> + if (port->ams != NONE_AMS)
> + tcpm_ams_start(port, port->ams, false);
> break;
> case VDM_STATE_ERR_SEND:
> /*
> @@ -1318,6 +1585,30 @@ static void vdm_run_state_machine(struct tcpm_port *port)
> tcpm_log(port, "VDM Tx error, retry");
> port->vdm_retries++;
> port->vdm_state = VDM_STATE_READY;
> + tcpm_ams_start(port, port->ams, false);
> + }
> + break;
> + case VDM_STATE_SEND_MESSAGE:
> + /* Prepare and send VDM */
> + memset(&msg, 0, sizeof(msg));
> + msg.header = PD_HEADER_LE(PD_DATA_VENDOR_DEF,
> + port->pwr_role,
> + port->data_role,
> + port->negotiated_rev,
> + port->message_id, port->vdo_count);
> + for (i = 0; i < port->vdo_count; i++)
> + msg.payload[i] = cpu_to_le32(port->vdo_data[i]);
> + res = tcpm_pd_transmit(port, TCPC_TX_SOP, &msg);
> + if (res < 0) {
> + port->vdm_state = VDM_STATE_ERR_SEND;
> + } else {
> + unsigned long timeout;
> +
> + port->vdm_retries = 0;
> + port->vdm_state = VDM_STATE_BUSY;
> + timeout = vdm_ready_timeout(port->vdo_data[0]);
> + mod_delayed_work(port->wq, &port->vdm_state_machine,
> + timeout);
> }
> break;
> default:
> @@ -1341,7 +1632,8 @@ static void vdm_state_machine_work(struct work_struct *work)
> prev_state = port->vdm_state;
> vdm_run_state_machine(port);
> } while (port->vdm_state != prev_state &&
> - port->vdm_state != VDM_STATE_BUSY);
> + port->vdm_state != VDM_STATE_BUSY &&
> + port->vdm_state != VDM_STATE_SEND_MESSAGE);
>
> mutex_unlock(&port->lock);
> }
> @@ -1671,6 +1963,7 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> {
> enum pd_ctrl_msg_type type = pd_header_type_le(msg->header);
> enum tcpm_state next_state;
> + int ret = 0;
>
> switch (type) {
> case PD_CTRL_GOOD_CRC:
> @@ -1785,11 +2078,19 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> case SOFT_RESET_SEND:
> port->message_id = 0;
> port->rx_msgid = -1;
> - if (port->pwr_role == TYPEC_SOURCE)
> - next_state = SRC_SEND_CAPABILITIES;
> - else
> - next_state = SNK_WAIT_CAPABILITIES;
> - tcpm_set_state(port, next_state, 0);
> + if (port->ams == SOFT_RESET_AMS)
> + tcpm_ams_start(port, port->ams, false);
> + if (port->pwr_role == TYPEC_SOURCE) {
> + port->upcoming_state = SRC_SEND_CAPABILITIES;
> + ret = tcpm_ams_start(port, POWER_NEGOTIATION,
> + true);
> + if (ret == -EOPNOTSUPP)
> + tcpm_set_state(port,
> + SRC_SEND_CAPABILITIES,
> + 0);
> + } else {
> + tcpm_set_state(port, SNK_WAIT_CAPABILITIES, 0);
> + }
> break;
> case DR_SWAP_SEND:
> tcpm_set_state(port, DR_SWAP_CHANGE_DR, 0);
> @@ -2555,13 +2856,6 @@ static bool tcpm_start_drp_toggling(struct tcpm_port *port,
> return false;
> }
>
> -static void tcpm_set_cc(struct tcpm_port *port, enum typec_cc_status cc)
> -{
> - tcpm_log(port, "cc:=%d", cc);
> - port->cc_req = cc;
> - port->tcpc->set_cc(port->tcpc, cc);
> -}
> -
> static int tcpm_init_vbus(struct tcpm_port *port)
> {
> int ret;
> @@ -2680,6 +2974,8 @@ static void tcpm_unregister_altmodes(struct tcpm_port *port)
>
> static void tcpm_reset_port(struct tcpm_port *port)
> {
> + port->in_ams = false;
> + port->ams = NONE_AMS;
> tcpm_unregister_altmodes(port);
> tcpm_typec_disconnect(port);
> port->attached = false;
> @@ -2843,6 +3139,7 @@ static void run_state_machine(struct tcpm_port *port)
> int ret;
> enum typec_pwr_opmode opmode;
> unsigned int msecs;
> + enum tcpm_state upcoming_state;
>
> port->enter_state = port->state;
> switch (port->state) {
> @@ -2945,7 +3242,14 @@ static void run_state_machine(struct tcpm_port *port)
> port->message_id = 0;
> port->rx_msgid = -1;
> port->explicit_contract = false;
> - tcpm_set_state(port, SRC_SEND_CAPABILITIES, 0);
> + /* SNK -> SRC POWER/FAST_ROLE_SWAP finished */
> + if (port->ams == POWER_ROLE_SWAP ||
> + port->ams == FAST_ROLE_SWAP)
> + tcpm_ams_start(port, port->ams, false);
> + port->upcoming_state = SRC_SEND_CAPABILITIES;
> + ret = tcpm_ams_start(port, POWER_NEGOTIATION, true);
> + if (ret == -EOPNOTSUPP)
> + tcpm_set_state(port, SRC_SEND_CAPABILITIES, 0);

The state machine changes are substantial. As mentioned above, this
will require a lot of review and substantial testing to ensure that existing
implementations are not negatively affected.

Quite frankly, my personal preference would be to try to find a less invasive
implementation.

> break;
> case SRC_SEND_CAPABILITIES:
> port->caps_count++;
> @@ -3003,6 +3307,18 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_swap_complete(port, 0);
> tcpm_typec_connect(port);
>
> + if (port->ams != NONE_AMS)
> + tcpm_ams_start(port, port->ams, false);
> + /*
> + * If previous AMS is interrupted, switch to the upcoming
> + * state.
> + */
> + upcoming_state = port->upcoming_state;
> + if (port->upcoming_state != INVALID_STATE) {
> + tcpm_switch_state(port, upcoming_state, 0);
> + break;
> + }

Any reason for assigning the next state to upcoming_state and not using
port->upcoming_state drectly ? The assignment followed by the re-use of
port->upcoming_state is odd and seems unnecessary.

Oh, I guess that tcpm_switch_state() is a macro and has the side effect
of changing port->upcoming_state. This just asks for trouble in future
patches, where people may not remember the context.

Another problem is that it is not well explained when tcpm_switch_state()
should now be called instead of tcpm_set_state(), with the only difference
being that the latter does not set upcoming_state to INVALID_STATE.
This is asking for even more trouble in the future, and really makes me
wonder if the new macro is worth it.

> +
> tcpm_check_send_discover(port);
> /*
> * 6.3.5
> @@ -3120,6 +3436,12 @@ static void run_state_machine(struct tcpm_port *port)
> port->message_id = 0;
> port->rx_msgid = -1;
> port->explicit_contract = false;
> +
> + if (port->ams == POWER_ROLE_SWAP ||
> + port->ams == FAST_ROLE_SWAP)
> + /* SRC -> SNK POWER/FAST_ROLE_SWAP finished */
> + tcpm_ams_start(port, port->ams, false);
> +
> tcpm_set_state(port, SNK_DISCOVERY, 0);
> break;
> case SNK_DISCOVERY:
> @@ -3169,7 +3491,7 @@ static void run_state_machine(struct tcpm_port *port)
> */
> if (port->vbus_never_low) {
> port->vbus_never_low = false;
> - tcpm_set_state(port, SOFT_RESET_SEND,
> + tcpm_set_state(port, SNK_SOFT_RESET,
> PD_T_SINK_WAIT_CAP);
> } else {
> tcpm_set_state(port, hard_reset_state(port),
> @@ -3222,9 +3544,21 @@ static void run_state_machine(struct tcpm_port *port)
>
> tcpm_swap_complete(port, 0);
> tcpm_typec_connect(port);
> - tcpm_check_send_discover(port);
> tcpm_pps_complete(port, port->pps_status);
>
> + if (port->ams != NONE_AMS)
> + tcpm_ams_start(port, port->ams, false);
> + /*
> + * If previous AMS is interrupted, switch to the upcoming
> + * state.
> + */
> + upcoming_state = port->upcoming_state;
> + if (port->upcoming_state != INVALID_STATE) {
> + tcpm_switch_state(port, upcoming_state, 0);
> + break;
> + }
> +
> + tcpm_check_send_discover(port);
> power_supply_changed(port->psy);
>
> break;
> @@ -3246,8 +3580,18 @@ static void run_state_machine(struct tcpm_port *port)
>
> /* Hard_Reset states */
> case HARD_RESET_SEND:
> - tcpm_pd_transmit(port, TCPC_TX_HARD_RESET, NULL);
> - tcpm_set_state(port, HARD_RESET_START, 0);
> + if (port->ams != NONE_AMS)
> + tcpm_ams_start(port, port->ams, false);
> + /*
> + * State machine will be directed to HARD_RESET_START,
> + * thus set upcoming_state to INVALID_STATE.
> + */
> + port->upcoming_state = INVALID_STATE;
> + ret = tcpm_ams_start(port, HARD_RESET, true);
> + if (ret == -EOPNOTSUPP) {
> + tcpm_pd_transmit(port, TCPC_TX_HARD_RESET, NULL);
> + tcpm_set_state(port, HARD_RESET_START, 0);
> + }
> break;
> case HARD_RESET_START:
> port->hard_reset_count++;
> @@ -3269,6 +3613,8 @@ static void run_state_machine(struct tcpm_port *port)
> break;
> case SRC_HARD_RESET_VBUS_ON:
> tcpm_set_vbus(port, true);
> + if (port->ams == HARD_RESET)
> + tcpm_ams_start(port, port->ams, false);
> port->tcpc->set_pd_rx(port->tcpc, true);
> tcpm_set_attached_state(port, true);
> tcpm_set_state(port, SRC_UNATTACHED, PD_T_PS_SOURCE_ON);
> @@ -3288,6 +3634,8 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_set_state(port, SNK_HARD_RESET_SINK_ON, PD_T_SAFE_0V);
> break;
> case SNK_HARD_RESET_WAIT_VBUS:
> + if (port->ams == HARD_RESET)
> + tcpm_ams_start(port, port->ams, false);
> /* Assume we're disconnected if VBUS doesn't come back. */
> tcpm_set_state(port, SNK_UNATTACHED,
> PD_T_SRC_RECOVER_MAX + PD_T_SRC_TURN_ON);
> @@ -3315,6 +3663,8 @@ static void run_state_machine(struct tcpm_port *port)
> 5000);
> tcpm_set_charge(port, true);
> }
> + if (port->ams == HARD_RESET)
> + tcpm_ams_start(port, port->ams, false);
> tcpm_set_attached_state(port, true);
> tcpm_set_state(port, SNK_STARTUP, 0);
> break;
> @@ -3324,10 +3674,23 @@ static void run_state_machine(struct tcpm_port *port)
> port->message_id = 0;
> port->rx_msgid = -1;
> tcpm_pd_send_control(port, PD_CTRL_ACCEPT);
> - if (port->pwr_role == TYPEC_SOURCE)
> - tcpm_set_state(port, SRC_SEND_CAPABILITIES, 0);
> - else
> + if (port->pwr_role == TYPEC_SOURCE) {
> + port->upcoming_state = SRC_SEND_CAPABILITIES;
> + ret = tcpm_ams_start(port, POWER_NEGOTIATION, true);
> + if (ret == -EOPNOTSUPP)
> + tcpm_set_state(port, SRC_SEND_CAPABILITIES, 0);
> + } else {
> tcpm_set_state(port, SNK_WAIT_CAPABILITIES, 0);
> + }
> + break;
> + case SRC_SOFT_RESET_WAIT_SNK_TX:
> + case SNK_SOFT_RESET:
> + if (port->ams != NONE_AMS)
> + tcpm_ams_start(port, port->ams, false);
> + port->upcoming_state = SOFT_RESET_SEND;
> + ret = tcpm_ams_start(port, SOFT_RESET_AMS, true);
> + if (ret == -EOPNOTSUPP)
> + tcpm_set_state(port, SOFT_RESET_SEND, 0);
> break;
> case SOFT_RESET_SEND:
> port->message_id = 0;
> @@ -3533,6 +3896,18 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_default_state(port),
> port->vbus_present ? PD_T_PS_SOURCE_OFF : 0);
> break;
> +
> + /* Collision Avoidance state */
> + case AMS_START:
> + if (port->upcoming_state == INVALID_STATE) {
> + tcpm_set_state(port, port->pwr_role == TYPEC_SOURCE ?
> + SRC_READY : SNK_READY, 0);
> + break;
> + }
> +
> + upcoming_state = port->upcoming_state;
> + tcpm_switch_state(port, upcoming_state, 0);
> + break;
> default:
> WARN(1, "Unexpected port state %d\n", port->state);
> break;
> @@ -3859,6 +4234,8 @@ static void _tcpm_pd_vbus_off(struct tcpm_port *port)
> static void _tcpm_pd_hard_reset(struct tcpm_port *port)
> {
> tcpm_log_force(port, "Received hard reset");
> + if (port->ams != NONE_AMS)
> + port->ams = NONE_AMS;
> /*
> * If we keep receiving hard reset requests, executing the hard reset
> * must have failed. Revert to error recovery if that happens.
> @@ -3976,7 +4353,14 @@ static int tcpm_dr_set(const struct typec_capability *cap,
> port->non_pd_role_swap = true;
> tcpm_set_state(port, PORT_RESET, 0);
> } else {
> - tcpm_set_state(port, DR_SWAP_SEND, 0);
> + port->upcoming_state = DR_SWAP_SEND;
> + ret = tcpm_ams_start(port, DATA_ROLE_SWAP, true);
> + if (ret == -EAGAIN) {
> + port->upcoming_state = INVALID_STATE;
> + goto port_unlock;
> + } else if (ret == -EOPNOTSUPP) {
> + tcpm_switch_state(port, DR_SWAP_SEND, 0);
> + }
> }
>
> port->swap_status = 0;
> @@ -4023,10 +4407,18 @@ static int tcpm_pr_set(const struct typec_capability *cap,
> goto port_unlock;
> }
>
> + port->upcoming_state = PR_SWAP_SEND;
> + ret = tcpm_ams_start(port, POWER_ROLE_SWAP, true);
> + if (ret == -EAGAIN) {
> + port->upcoming_state = INVALID_STATE;
> + goto port_unlock;
> + } else if (ret == -EOPNOTSUPP) {
> + tcpm_switch_state(port, PR_SWAP_SEND, 0);
> + }
> +
> port->swap_status = 0;
> port->swap_pending = true;
> reinit_completion(&port->swap_complete);
> - tcpm_set_state(port, PR_SWAP_SEND, 0);
> mutex_unlock(&port->lock);
>
> if (!wait_for_completion_timeout(&port->swap_complete,
> @@ -4063,10 +4455,18 @@ static int tcpm_vconn_set(const struct typec_capability *cap,
> goto port_unlock;
> }
>
> + port->upcoming_state = VCONN_SWAP_SEND;
> + ret = tcpm_ams_start(port, VCONN_SWAP, true);
> + if (ret == -EAGAIN) {
> + port->upcoming_state = INVALID_STATE;
> + goto port_unlock;
> + } else if (ret == -EOPNOTSUPP) {
> + tcpm_switch_state(port, VCONN_SWAP_SEND, 0);
> + }
> +
> port->swap_status = 0;
> port->swap_pending = true;
> reinit_completion(&port->swap_complete);
> - tcpm_set_state(port, VCONN_SWAP_SEND, 0);
> mutex_unlock(&port->lock);
>
> if (!wait_for_completion_timeout(&port->swap_complete,
> @@ -4131,6 +4531,13 @@ static int tcpm_pps_set_op_curr(struct tcpm_port *port, u16 op_curr)
> goto port_unlock;
> }
>
> + port->upcoming_state = SNK_NEGOTIATE_PPS_CAPABILITIES;
> + ret = tcpm_ams_start(port, POWER_NEGOTIATION, true);
> + if (ret == -EAGAIN || ret == -EOPNOTSUPP) {
> + port->upcoming_state = INVALID_STATE;
> + goto port_unlock;
> + }
> +
> /* Round down operating current to align with PPS valid steps */
> op_curr = op_curr - (op_curr % RDO_PROG_CURR_MA_STEP);
>
> @@ -4138,7 +4545,6 @@ static int tcpm_pps_set_op_curr(struct tcpm_port *port, u16 op_curr)
> port->pps_data.op_curr = op_curr;
> port->pps_status = 0;
> port->pps_pending = true;
> - tcpm_set_state(port, SNK_NEGOTIATE_PPS_CAPABILITIES, 0);
> mutex_unlock(&port->lock);
>
> if (!wait_for_completion_timeout(&port->pps_complete,
> @@ -4187,6 +4593,13 @@ static int tcpm_pps_set_out_volt(struct tcpm_port *port, u16 out_volt)
> goto port_unlock;
> }
>
> + port->upcoming_state = SNK_NEGOTIATE_PPS_CAPABILITIES;
> + ret = tcpm_ams_start(port, POWER_NEGOTIATION, true);
> + if (ret == -EAGAIN || ret == -EOPNOTSUPP) {
> + port->upcoming_state = INVALID_STATE;
> + goto port_unlock;
> + }
> +
> /* Round down output voltage to align with PPS valid steps */
> out_volt = out_volt - (out_volt % RDO_PROG_VOLT_MV_STEP);
>
> @@ -4194,7 +4607,6 @@ static int tcpm_pps_set_out_volt(struct tcpm_port *port, u16 out_volt)
> port->pps_data.out_volt = out_volt;
> port->pps_status = 0;
> port->pps_pending = true;
> - tcpm_set_state(port, SNK_NEGOTIATE_PPS_CAPABILITIES, 0);
> mutex_unlock(&port->lock);
>
> if (!wait_for_completion_timeout(&port->pps_complete,
> @@ -4234,6 +4646,16 @@ static int tcpm_pps_activate(struct tcpm_port *port, bool activate)
> goto port_unlock;
> }
>
> + if (activate)
> + port->upcoming_state = SNK_NEGOTIATE_PPS_CAPABILITIES;
> + else
> + port->upcoming_state = SNK_NEGOTIATE_CAPABILITIES;
> + ret = tcpm_ams_start(port, POWER_NEGOTIATION, true);
> + if (ret == -EAGAIN || ret == -EOPNOTSUPP) {
> + port->upcoming_state = INVALID_STATE;
> + goto port_unlock;
> + }
> +
> reinit_completion(&port->pps_complete);
> port->pps_status = 0;
> port->pps_pending = true;
> @@ -4242,9 +4664,6 @@ static int tcpm_pps_activate(struct tcpm_port *port, bool activate)
> if (activate) {
> port->pps_data.out_volt = port->supply_voltage;
> port->pps_data.op_curr = port->current_limit;
> - tcpm_set_state(port, SNK_NEGOTIATE_PPS_CAPABILITIES, 0);
> - } else {
> - tcpm_set_state(port, SNK_NEGOTIATE_CAPABILITIES, 0);
> }
> mutex_unlock(&port->lock);
>
> diff --git a/include/linux/usb/pd.h b/include/linux/usb/pd.h
> index f2162e0fe531..6296ef65dab6 100644
> --- a/include/linux/usb/pd.h
> +++ b/include/linux/usb/pd.h
> @@ -451,6 +451,7 @@ static inline unsigned int rdo_max_power(u32 rdo)
> #define PD_T_ERROR_RECOVERY 100 /* minimum 25 is insufficient */
> #define PD_T_SRCSWAPSTDBY 625 /* Maximum of 650ms */
> #define PD_T_NEWSRC 250 /* Maximum of 275ms */
> +#define PD_T_SINK_TX 16 /* 16 - 20 ms */
>
> #define PD_T_DRP_TRY 100 /* 75 - 150 ms */
> #define PD_T_DRP_TRYWAIT 600 /* 400 - 800 ms */
> diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
> index 0c532ca3f079..419929a10549 100644
> --- a/include/linux/usb/tcpm.h
> +++ b/include/linux/usb/tcpm.h
> @@ -28,6 +28,10 @@ enum typec_cc_status {
> TYPEC_CC_RP_3_0,
> };
>
> +/* Collision Avoidance */
> +#define SINK_TX_NG TYPEC_CC_RP_1_5
> +#define SINK_TX_OK TYPEC_CC_RP_3_0
> +
> enum typec_cc_polarity {
> TYPEC_POLARITY_CC1,
> TYPEC_POLARITY_CC2,
> --
> 2.21.0.225.g810b269d1ac-goog
>

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