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

[Guenter Roeck]

On Thu, Sep 29, 2016 at 11:41 PM, Jun Li <jun.li@xxxxxxx> wrote:
> 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?
>

I should be able to send out a new version early next week, after
applying and testing your suggested changes. I'll also try to make a
test branch available in my repository at kernel.org.

Guenter

> 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;
>> >>