RE: [RFC PATCH v3 1/2] usb: typec: USB Type-C Port Manager (tcpm)

[Jun Li]

Hi,

> -----Original Message-----
> From: Guenter Roeck [mailto:groeck@xxxxxxxxxx]
> Sent: Friday, September 30, 2016 12:37 AM
> To: Jun Li <jun.li@xxxxxxx>
> Cc: Guenter Roeck <groeck@xxxxxxxxxxxx>; Felipe Balbi
> <felipe.balbi@xxxxxxxxxxxxxxx>; Chandra Sekhar Anagani
> <chandra.sekhar.anagani@xxxxxxxxx>; Bruce Ashfield
> <bruce.ashfield@xxxxxxxxxxxxx>; Bin Gao <bin.gao@xxxxxxxxx>; Pranav Tipnis
> <pranav.tipnis@xxxxxxxxx>; Heikki Krogerus
> <heikki.krogerus@xxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux-
> usb@xxxxxxxxxxxxxxx
> Subject: Re: [RFC PATCH v3 1/2] usb: typec: USB Type-C Port Manager (tcpm)
> 
> On Thu, Sep 29, 2016 at 7:35 AM, Jun Li <jun.li@xxxxxxx> wrote:
> > Hi Guenter,
> >
> >> -----Original Message-----
> >> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-
> >> owner@xxxxxxxxxxxxxxx] On Behalf Of Guenter Roeck
> >> Sent: Wednesday, August 24, 2016 5:11 AM
> >> To: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
> >> Cc: Chandra Sekhar Anagani <chandra.sekhar.anagani@xxxxxxxxx>; Bruce
> >> Ashfield <bruce.ashfield@xxxxxxxxxxxxx>; Bin Gao <bin.gao@xxxxxxxxx>;
> >> Pranav Tipnis <pranav.tipnis@xxxxxxxxx>; Heikki Krogerus
> >> <heikki.krogerus@xxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx;
> >> linux- usb@xxxxxxxxxxxxxxx; Guenter Roeck <groeck@xxxxxxxxxxxx>
> >> Subject: [RFC PATCH v3 1/2] usb: typec: USB Type-C Port Manager
> >> (tcpm)
> >>
> >> This driver implements the USB Type-C Power Delivery state machine
> >> for both source and sink ports. Alternate mode support is not fully
> >> implemented.
> >>
> >> The driver attaches to the USB Type-C class code implemented in the
> >> following patches.
> >>
> >>       usb: typec: add driver for Intel Whiskey Cove PMIC USB Type-C PHY
> >>       usb: USB Type-C connector class
> >>
> >> This driver only implements the state machine. Lower level drivers
> >> are responsible for
> >> - Reporting VBUS status and activating VBUS
> >> - Setting CC lines and providing CC line status
> >> - Setting line polarity
> >> - Activating and deactivating VCONN
> >> - Setting the current limit
> >> - Activating and deactivating PD message transfers
> >> - Sending and receiving PD messages
> >>
> >> The driver provides both a functional API as well as callbacks for
> >> lower level drivers.
> >>
> >> Signed-off-by: Guenter Roeck <groeck@xxxxxxxxxxxx>
> >> ---
> >> v3:
> >> - Improve TCPM state machine resiliency if there are spurious CC line
> >> changes
> >>   while the state machine is in a transient change (waiting for a
> >> timeout)
> >> - Update current limit after CC voltage level changes on a port which
> >> is not
> >>   PD capable.
> >>
> >> v2:
> >> - Only update polarity if setting it was successful
> >>   If setting the CC line polarity in the driver was not successful,
> >>   don't update the internal polarity state.
> >> - All PD messages are little endian; convert to and from CPU endianness.
> >> - Avoid comparisons against NULL.
> >> - Use u8/u16/u32 instead of uint8_t/uint16_t/uint32_t consistently.
> >> - Callbacks into tcpm need to be lockless to avoid timing problems
> >>   in low level drivers.
> >> - Simplify callbacks; tcpm can request the current state of cc/vbus
> >>   when it is ready to use it.
> >>
> >>  drivers/usb/typec/Kconfig  |    7 +
> >>  drivers/usb/typec/Makefile |    1 +
> >>  drivers/usb/typec/tcpm.c   | 3163
> >> ++++++++++++++++++++++++++++++++++++++++++++
> >>  drivers/usb/typec/tcpm.h   |  137 ++
> >>  include/linux/usb/pd.h     |  282 ++++
> >>  include/linux/usb/pd_bdo.h |   31 +
> >>  include/linux/usb/pd_vdo.h |  412 ++++++
> >>  7 files changed, 4033 insertions(+)
> >>  create mode 100644 drivers/usb/typec/tcpm.c  create mode 100644
> >> drivers/usb/typec/tcpm.h  create mode 100644 include/linux/usb/pd.h
> >> create mode 100644 include/linux/usb/pd_bdo.h  create mode 100644
> >> include/linux/usb/pd_vdo.h
> >>
> >
> > ...
> >
> >> +
> >> +static void run_state_machine(struct tcpm_port *port) {
> >> +     int ret;
> >> +
> >> +     port->enter_state = port->state;
> >> +     switch (port->state) {
> >> +     /* SRC states */
> >> +     case SRC_UNATTACHED:
> >> +             tcpm_swap_complete(port, -ENOTCONN);
> >> +             tcpm_src_detach(port);
> >> +             tcpm_set_cc(port, TYPEC_CC_RP_DEF);
> >> +             if (port->typec_caps.type == TYPEC_PORT_DRP)
> >> +                     tcpm_set_state(port, SNK_UNATTACHED,
> >> + PD_T_DRP_SNK);
> >
> > With this and below, after disconnect, the DRP port state machine will
> > be in infinite loop of state transition between SRC_UNATTACHED <-->
> > SNK_UNATTACHED, correct?
> >
> 
> Only while disconnected. It tries to alternatively connect as source and
> as sink (being configured as DRP). Once a CC line state change is reported
> it will transition out. I have a newer version of the patch (not yet
> published) which supports DRP toggling by the TCPC. With that enabled,
> TCPM does not change states until a CC state change is reported.
> 
Great, that way will be better, do you plan post your newer patch recently? 

Thanks
Li Jun

> Guenter
> 
> > Li Jun
> > ...
> >
> >> +     /* SNK states */
> >> +     case SNK_UNATTACHED:
> >> +             tcpm_swap_complete(port, -ENOTCONN);
> >> +             tcpm_snk_detach(port);
> >> +             tcpm_set_cc(port, TYPEC_CC_RD);
> >> +             if (port->typec_caps.type == TYPEC_PORT_DRP)
> >> +                     tcpm_set_state(port, SRC_UNATTACHED,
> PD_T_DRP_SRC);
> >> +             break;
> >>