Re: [PATCH v6 09/14] usb: typec: tcpm: Add support for Sink Fast Role SWAP(FRS)

Badhri Jagan Sridharan
2020-09-17T10:24:43Z

On Tue, Sep 15, 2020 at 6:20 AM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> On Mon, Aug 31, 2020 at 07:59:22PM -0700, Badhri Jagan Sridharan wrote:
> > PD 3.0 spec defines a new mechanism for power role swap called
> > Fast role swap. This change enables TCPM to support FRS when
> > acting as sink.
> >
> > Once the explicit contract is negotiated, sink port is
> > expected to query the source port for sink caps to
> > determine whether the source is FRS capable.
> > Bits 23 & 24 of fixed pdo of the sink caps from the source, when
> > set, indicates the current needed by the source when fast role
> > swap is in progress(Implicit contract phasae). 0 indicates that
> > the source does not support Fast Role Swap.
> >
> > Upon receiving the FRS signal from the source,
> > TCPC(TCPM_FRS_EVENT) informs TCPM to start the Fast role swap sequence.
> >
> > 1. TCPM sends FRS PD message: FR_SWAP_SEND
> > 2. If response is not received within the expiry of
> > SenderResponseTimer, Error recovery is triggered.:
> > FR_SWAP_SEND_TIMEOUT
> > 3. Upon receipt of the accept message, TCPM waits for
> > PSSourceOffTimer for PS_READY message from the partner:
> > FR_SWAP_SNK_SRC_NEW_SINK_READY.
> >
> > TCPC is expected to autonomously turn on vbus once the FRS
> > signal is received and vbus voltage falls below vsafe5v within
> > tSrcFrSwap. This is different from traditional power role swap
> > where the vbus sourcing is turned on by TCPM.
> >
> > 4. By this time, TCPC most likely would have started to
> > source vbus, TCPM waits for tSrcFrSwap to see if the
> > lower level TCPC driver signals TCPM_SOURCING_VBUS event:
> > FR_SWAP_SNK_SRC_SOURCE_VBUS_APPLIED.
> > 5. When TCPC signals sourcing vbus, TCPM sends PS_READY msg and
> > changes the CC pin from Rd to Rp. This is the end of fast
> > role swap sequence and TCPM initiates the sequnce to negotiate
> > explicit contract by transitioning into SRC_STARTUP after
> > SwapSrcStart.
> >
> > The code is written based on the sequence described in "Figure 8-107:
> > Dual-role Port in Sink to Source Fast Role Swap State Diagram" of
> > USB Power Delivery Specification Revision 3.0, Version 1.2.
> >
> > Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
> > ---
> > Changes since v1:
> > - Changing patch version to v6 to fix version number confusion.
> > - Rebased on top of usb-next and resolved conflicts due to the below
> > changes:
> > 3ed8e1c2ac99 usb: typec: tcpm: Migrate workqueue to RT priority for processing events
> > 6bbe2a90a0bb usb: typec: tcpm: During PR_SWAP, source caps should be sent only after tSwapSourceStart
> > - enable_frs sequence is now run as part of the same kthread that runs
> > the state machines.
> > - Fixed the implicit fallthrough warning in the switch case for
> > FR_SWAP_CANCEL case.
> > ---
> > drivers/usb/typec/tcpm/tcpm.c | 217 +++++++++++++++++++++++++++++++++-
> > include/linux/usb/pd.h | 19 +--
> > include/linux/usb/tcpm.h | 8 +-
> > include/linux/usb/typec.h | 13 ++
> > 4 files changed, 245 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index 92806547f485..083e7af107b2 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -106,6 +106,13 @@
> > S(VCONN_SWAP_TURN_ON_VCONN), \
> > S(VCONN_SWAP_TURN_OFF_VCONN), \
> > \
> > + S(FR_SWAP_SEND), \
> > + S(FR_SWAP_SEND_TIMEOUT), \
> > + S(FR_SWAP_SNK_SRC_TRANSITION_TO_OFF), \
> > + S(FR_SWAP_SNK_SRC_NEW_SINK_READY), \
> > + S(FR_SWAP_SNK_SRC_SOURCE_VBUS_APPLIED), \
> > + S(FR_SWAP_CANCEL), \
> > + \
> > S(SNK_TRY), \
> > S(SNK_TRY_WAIT), \
> > S(SNK_TRY_WAIT_DEBOUNCE), \
> > @@ -127,6 +134,9 @@
> > S(GET_PPS_STATUS_SEND), \
> > S(GET_PPS_STATUS_SEND_TIMEOUT), \
> > \
> > + S(GET_SINK_CAP), \
> > + S(GET_SINK_CAP_TIMEOUT), \
> > + \
> > S(ERROR_RECOVERY), \
> > S(PORT_RESET), \
> > S(PORT_RESET_WAIT_OFF)
> > @@ -175,6 +185,8 @@ enum adev_actions {
> > #define TCPM_CC_EVENT BIT(0)
> > #define TCPM_VBUS_EVENT BIT(1)
> > #define TCPM_RESET_EVENT BIT(2)
> > +#define TCPM_FRS_EVENT BIT(3)
> > +#define TCPM_SOURCING_VBUS BIT(4)
> >
> > #define LOG_BUFFER_ENTRIES 1024
> > #define LOG_BUFFER_ENTRY_SIZE 128
> > @@ -184,6 +196,8 @@ enum adev_actions {
> > #define SVID_DISCOVERY_MAX 16
> > #define ALTMODE_DISCOVERY_MAX (SVID_DISCOVERY_MAX * MODE_DISCOVERY_MAX)
> >
> > +#define GET_SINK_CAP_RETRY_MS 100
> > +
> > struct pd_mode_data {
> > int svid_index; /* current SVID index */
> > int nsvids;
> > @@ -261,6 +275,8 @@ struct tcpm_port {
> > struct kthread_work state_machine;
> > struct hrtimer vdm_state_machine_timer;
> > struct kthread_work vdm_state_machine;
> > + struct hrtimer enable_frs_timer;
> > + struct kthread_work enable_frs;
> > bool state_machine_running;
> >
> > struct completion tx_complete;
> > @@ -335,6 +351,12 @@ struct tcpm_port {
> > /* port belongs to a self powered device */
> > bool self_powered;
> >
> > + /* FRS */
> > + enum frs_typec_current frs_current;
>
> Do you use this member anywhere?
>
> I can't see anywhere it being used, but I think you should use it
> instead the one in port_caps.
Yes I started with having it here and then switched to port_caps
while forgetting this !
Have gone back to using the one here.

>
> > + /* Sink caps have been queried */
> > + bool sink_cap_done;
> > +
> > #ifdef CONFIG_DEBUG_FS
> > struct dentry *dentry;
> > struct mutex logbuffer_lock; /* log buffer access lock */
> > @@ -940,6 +962,16 @@ static void mod_vdm_delayed_work(struct tcpm_port *port, unsigned int delay_ms)
> > }
> > }
>
> <snip>
>
> > diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
> > index 9cb1bec94b71..2ec7451a14ab 100644
> > --- a/include/linux/usb/typec.h
> > +++ b/include/linux/usb/typec.h
> > @@ -204,6 +204,18 @@ struct typec_operations {
> > enum typec_port_type type);
> > };
> >
> > +/*
> > + * Initial current capability of the new source when vSafe5V is applied during PD3.0 Fast Role Swap.
> > + * Based on "Table 6-14 Fixed Supply PDO - Sink" of "USB Power Delivery Specification Revision 3.0,
> > + * Version 1.2"
> > + */
> > +enum frs_typec_current {
> > + FRS_NOT_SUPPORTED,
> > + FRS_DEFAULT_POWER,
> > + FRS_5V_1P5A,
> > + FRS_5V_3A,
> > +};
> > +
> > /*
> > * struct typec_capability - USB Type-C Port Capabilities
> > * @type: Supported power role of the port
> > @@ -226,6 +238,7 @@ struct typec_capability {
> > int prefer_role;
> > enum typec_accessory accessory[TYPEC_MAX_ACCESSORY];
> > unsigned int orientation_aware:1;
> > + enum frs_typec_current frs_current;
>
> So forget about this. We can add it here if/when there is another
> driver that needs that. You already have that member in struct
> tcpm_port, so just use that for now.
>
> And you can also introduce enum frs_typec_current in tcpm.c for now.

Sure ! Done in v7.

>
> > struct fwnode_handle *fwnode;
> > void *driver_data;
> > --
> > 2.28.0.402.g5ffc5be6b7-goog
>
> thanks,
>
> --
> heikki