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Message-ID: <CAGZ6i=0=shyW-Y7G+SrySi7Sum8qnjhpOwp=vC+SUmwHkbQMrw@mail.gmail.com>
Date: Tue, 17 Aug 2021 18:32:55 +0800
From: Kyle Tso <kyletso@...gle.com>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: linux@...ck-us.net, gregkh@...uxfoundation.org, badhri@...gle.com,
linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: tcpm: Raise vdm_sm_running flag only when VDM
SM is running
On Tue, Aug 17, 2021 at 5:39 PM Heikki Krogerus
<heikki.krogerus@...ux.intel.com> wrote:
>
> On Mon, Aug 16, 2021 at 03:54:49PM +0800, Kyle Tso wrote:
> > If the port is going to send Discover_Identity Message, vdm_sm_running
> > flag was intentionally set before entering Ready States in order to
> > avoid the conflict because the port and the port partner might start
> > AMS at almost the same time after entering Ready States.
> >
> > However, the original design has a problem. When the port is doing
> > DR_SWAP from Device to Host, it raises the flag. Later in the
> > tcpm_send_discover_work, the flag blocks the procedure of sending the
> > Discover_Identity and it might never be cleared until disconnection.
>
> This is a bit off-topic, but I just asked this in another thread: Why
> do we have to do discovery with data role swap?
>
> thanks,
>
This can be separated into two cases:
1. in PD2: If the port is originally UFP, it cannot send
Discover_Identity Message according to the Spec. And then DR_SWAP
happens. The port becomes DFP, and now it can do that.
2. in PD3: DFP and UFP are allowed to send Discover_Identity Message
and the responses may differ based on which roles they are active on.
Quote from the PD3 Spec:
```
The Discover Identity Command Shall be used to determine the identity
and/or capabilities of the Port Partner. The following products Shall
return a Discover Identity Command ACK in response to a Discover
Identity Command request sent to SOP:
• A PD-Capable UFP that supports Modal Operation.
• A PD-Capable product that has multiple DFPs.
• A PD-Capable [USB4] product.
```
thanks,
Kyle
> > Since there exists another flag send_discover representing that the port
> > is going to send Discover_Identity or not, it is enough to use that flag
> > to prevent the conflict. Also change the timing of the set/clear of
> > vdm_sm_running to indicate whether the VDM SM is actually running or
> > not.
> >
> > Fixes: c34e85fa69b9 ("usb: typec: tcpm: Send DISCOVER_IDENTITY from dedicated work")
> > Cc: Badhri Jagan Sridharan <badhri@...gle.com>
> > Signed-off-by: Kyle Tso <kyletso@...gle.com>
> > ---
> > drivers/usb/typec/tcpm/tcpm.c | 81 ++++++++++++++++-------------------
> > 1 file changed, 38 insertions(+), 43 deletions(-)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index 5b22a1c931a9..c05ddfbaff08 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -341,6 +341,7 @@ struct tcpm_port {
> > bool vbus_source;
> > bool vbus_charge;
> >
> > + /* Set to true when Discover_Identity Command is expected to be sent in Ready states. */
> > bool send_discover;
> > bool op_vsafe5v;
> >
> > @@ -370,6 +371,7 @@ struct tcpm_port {
> > struct hrtimer send_discover_timer;
> > struct kthread_work send_discover_work;
> > bool state_machine_running;
> > + /* Set to true when VDM State Machine has following actions. */
> > bool vdm_sm_running;
> >
> > struct completion tx_complete;
> > @@ -1431,6 +1433,7 @@ static void tcpm_queue_vdm(struct tcpm_port *port, const u32 header,
> > /* Set ready, vdm state machine will actually send */
> > port->vdm_retries = 0;
> > port->vdm_state = VDM_STATE_READY;
> > + port->vdm_sm_running = true;
> >
> > mod_vdm_delayed_work(port, 0);
> > }
> > @@ -1673,7 +1676,6 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> > rlen = 1;
> > } else {
> > tcpm_register_partner_altmodes(port);
> > - port->vdm_sm_running = false;
> > }
> > break;
> > case CMD_ENTER_MODE:
> > @@ -1721,14 +1723,12 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> > (VDO_SVDM_VERS(svdm_version));
> > break;
> > }
> > - port->vdm_sm_running = false;
> > break;
> > default:
> > response[0] = p[0] | VDO_CMDT(CMDT_RSP_NAK);
> > rlen = 1;
> > response[0] = (response[0] & ~VDO_SVDM_VERS_MASK) |
> > (VDO_SVDM_VERS(svdm_version));
> > - port->vdm_sm_running = false;
> > break;
> > }
> >
> > @@ -1765,6 +1765,20 @@ static void tcpm_handle_vdm_request(struct tcpm_port *port,
> > }
> >
> > if (PD_VDO_SVDM(p[0])) {
> > + /*
> > + * Here a SVDM is received (INIT or RSP or unknown). Set the vdm_sm_running in
> > + * advance because we are dropping the lock but may send VDMs soon.
> > + * For the cases of INIT received:
> > + * - If no response to send, it will be cleared later in this function.
> > + * - If there are responses to send, it will be cleared in the state machine.
> > + * For the cases of RSP received:
> > + * - If no further INIT to send, it will be cleared later in this function.
> > + * - Otherwise, it will be cleared in the state machine if timeout or it will go
> > + * back here until no further INIT to send.
> > + * For the cases of unknown type received:
> > + * - We will send NAK and the flag will be cleared in the state machine.
> > + */
> > + port->vdm_sm_running = true;
> > rlen = tcpm_pd_svdm(port, adev, p, cnt, response, &adev_action);
> > } else {
> > if (port->negotiated_rev >= PD_REV30)
> > @@ -1833,6 +1847,8 @@ static void tcpm_handle_vdm_request(struct tcpm_port *port,
> >
> > if (rlen > 0)
> > tcpm_queue_vdm(port, response[0], &response[1], rlen - 1);
> > + else
> > + port->vdm_sm_running = false;
> > }
> >
> > static void tcpm_send_vdm(struct tcpm_port *port, u32 vid, int cmd,
> > @@ -1898,8 +1914,10 @@ static void vdm_run_state_machine(struct tcpm_port *port)
> > * if there's traffic or we're not in PDO ready state don't send
> > * a VDM.
> > */
> > - if (port->state != SRC_READY && port->state != SNK_READY)
> > + if (port->state != SRC_READY && port->state != SNK_READY) {
> > + port->vdm_sm_running = false;
> > break;
> > + }
> >
> > /* TODO: AMS operation for Unstructured VDM */
> > if (PD_VDO_SVDM(vdo_hdr) && PD_VDO_CMDT(vdo_hdr) == CMDT_INIT) {
> > @@ -2555,10 +2573,6 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> > TYPEC_PWR_MODE_PD,
> > port->pps_data.active,
> > port->supply_voltage);
> > - /* Set VDM running flag ASAP */
> > - if (port->data_role == TYPEC_HOST &&
> > - port->send_discover)
> > - port->vdm_sm_running = true;
> > tcpm_set_state(port, SNK_READY, 0);
> > } else {
> > /*
> > @@ -2596,14 +2610,10 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> > switch (port->state) {
> > case SNK_NEGOTIATE_CAPABILITIES:
> > /* USB PD specification, Figure 8-43 */
> > - if (port->explicit_contract) {
> > + if (port->explicit_contract)
> > next_state = SNK_READY;
> > - if (port->data_role == TYPEC_HOST &&
> > - port->send_discover)
> > - port->vdm_sm_running = true;
> > - } else {
> > + else
> > next_state = SNK_WAIT_CAPABILITIES;
> > - }
> >
> > /* Threshold was relaxed before sending Request. Restore it back. */
> > tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> > @@ -2618,10 +2628,6 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> > port->pps_status = (type == PD_CTRL_WAIT ?
> > -EAGAIN : -EOPNOTSUPP);
> >
> > - if (port->data_role == TYPEC_HOST &&
> > - port->send_discover)
> > - port->vdm_sm_running = true;
> > -
> > /* Threshold was relaxed before sending Request. Restore it back. */
> > tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> > port->pps_data.active,
> > @@ -2697,10 +2703,6 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> > }
> > break;
> > case DR_SWAP_SEND:
> > - if (port->data_role == TYPEC_DEVICE &&
> > - port->send_discover)
> > - port->vdm_sm_running = true;
> > -
> > tcpm_set_state(port, DR_SWAP_CHANGE_DR, 0);
> > break;
> > case PR_SWAP_SEND:
> > @@ -2738,7 +2740,7 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> > PD_MSG_CTRL_NOT_SUPP,
> > NONE_AMS);
> > } else {
> > - if (port->vdm_sm_running) {
> > + if (port->send_discover) {
> > tcpm_queue_message(port, PD_MSG_CTRL_WAIT);
> > break;
> > }
> > @@ -2754,7 +2756,7 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> > PD_MSG_CTRL_NOT_SUPP,
> > NONE_AMS);
> > } else {
> > - if (port->vdm_sm_running) {
> > + if (port->send_discover) {
> > tcpm_queue_message(port, PD_MSG_CTRL_WAIT);
> > break;
> > }
> > @@ -2763,7 +2765,7 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> > }
> > break;
> > case PD_CTRL_VCONN_SWAP:
> > - if (port->vdm_sm_running) {
> > + if (port->send_discover) {
> > tcpm_queue_message(port, PD_MSG_CTRL_WAIT);
> > break;
> > }
> > @@ -4479,18 +4481,20 @@ static void run_state_machine(struct tcpm_port *port)
> > /* DR_Swap states */
> > case DR_SWAP_SEND:
> > tcpm_pd_send_control(port, PD_CTRL_DR_SWAP);
> > + if (port->data_role == TYPEC_DEVICE || port->negotiated_rev > PD_REV20)
> > + port->send_discover = true;
> > tcpm_set_state_cond(port, DR_SWAP_SEND_TIMEOUT,
> > PD_T_SENDER_RESPONSE);
> > break;
> > case DR_SWAP_ACCEPT:
> > tcpm_pd_send_control(port, PD_CTRL_ACCEPT);
> > - /* Set VDM state machine running flag ASAP */
> > - if (port->data_role == TYPEC_DEVICE && port->send_discover)
> > - port->vdm_sm_running = true;
> > + if (port->data_role == TYPEC_DEVICE || port->negotiated_rev > PD_REV20)
> > + port->send_discover = true;
> > tcpm_set_state_cond(port, DR_SWAP_CHANGE_DR, 0);
> > break;
> > case DR_SWAP_SEND_TIMEOUT:
> > tcpm_swap_complete(port, -ETIMEDOUT);
> > + port->send_discover = false;
> > tcpm_ams_finish(port);
> > tcpm_set_state(port, ready_state(port), 0);
> > break;
> > @@ -4502,7 +4506,6 @@ static void run_state_machine(struct tcpm_port *port)
> > } else {
> > tcpm_set_roles(port, true, port->pwr_role,
> > TYPEC_HOST);
> > - port->send_discover = true;
> > }
> > tcpm_ams_finish(port);
> > tcpm_set_state(port, ready_state(port), 0);
> > @@ -4645,8 +4648,6 @@ static void run_state_machine(struct tcpm_port *port)
> > break;
> > case VCONN_SWAP_SEND_TIMEOUT:
> > tcpm_swap_complete(port, -ETIMEDOUT);
> > - if (port->data_role == TYPEC_HOST && port->send_discover)
> > - port->vdm_sm_running = true;
> > tcpm_set_state(port, ready_state(port), 0);
> > break;
> > case VCONN_SWAP_START:
> > @@ -4662,14 +4663,10 @@ static void run_state_machine(struct tcpm_port *port)
> > case VCONN_SWAP_TURN_ON_VCONN:
> > tcpm_set_vconn(port, true);
> > tcpm_pd_send_control(port, PD_CTRL_PS_RDY);
> > - if (port->data_role == TYPEC_HOST && port->send_discover)
> > - port->vdm_sm_running = true;
> > tcpm_set_state(port, ready_state(port), 0);
> > break;
> > case VCONN_SWAP_TURN_OFF_VCONN:
> > tcpm_set_vconn(port, false);
> > - if (port->data_role == TYPEC_HOST && port->send_discover)
> > - port->vdm_sm_running = true;
> > tcpm_set_state(port, ready_state(port), 0);
> > break;
> >
> > @@ -4677,8 +4674,6 @@ static void run_state_machine(struct tcpm_port *port)
> > case PR_SWAP_CANCEL:
> > case VCONN_SWAP_CANCEL:
> > tcpm_swap_complete(port, port->swap_status);
> > - if (port->data_role == TYPEC_HOST && port->send_discover)
> > - port->vdm_sm_running = true;
> > if (port->pwr_role == TYPEC_SOURCE)
> > tcpm_set_state(port, SRC_READY, 0);
> > else
> > @@ -5028,9 +5023,6 @@ static void _tcpm_pd_vbus_on(struct tcpm_port *port)
> > switch (port->state) {
> > case SNK_TRANSITION_SINK_VBUS:
> > port->explicit_contract = true;
> > - /* Set the VDM flag ASAP */
> > - if (port->data_role == TYPEC_HOST && port->send_discover)
> > - port->vdm_sm_running = true;
> > tcpm_set_state(port, SNK_READY, 0);
> > break;
> > case SNK_DISCOVERY:
> > @@ -5425,15 +5417,18 @@ static void tcpm_send_discover_work(struct kthread_work *work)
> > if (!port->send_discover)
> > goto unlock;
> >
> > + if (port->data_role == TYPEC_DEVICE && port->negotiated_rev < PD_REV30) {
> > + port->send_discover = false;
> > + goto unlock;
> > + }
> > +
> > /* Retry if the port is not idle */
> > if ((port->state != SRC_READY && port->state != SNK_READY) || port->vdm_sm_running) {
> > mod_send_discover_delayed_work(port, SEND_DISCOVER_RETRY_MS);
> > goto unlock;
> > }
> >
> > - /* Only send the Message if the port is host for PD rev2.0 */
> > - if (port->data_role == TYPEC_HOST || port->negotiated_rev > PD_REV20)
> > - tcpm_send_vdm(port, USB_SID_PD, CMD_DISCOVER_IDENT, NULL, 0);
> > + tcpm_send_vdm(port, USB_SID_PD, CMD_DISCOVER_IDENT, NULL, 0);
> >
> > unlock:
> > mutex_unlock(&port->lock);
> > --
> > 2.33.0.rc1.237.g0d66db33f3-goog
>
> --
> heikki
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