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

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