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References: <20210205033415.3320439-1-kyletso@google.com> <20210205033415.3320439-4-kyletso@google.com>
 <20210212041756.GC103223@roeck-us.net>
In-Reply-To: <20210212041756.GC103223@roeck-us.net>
From:   Kyle Tso <kyletso@google.com>
Date:   Fri, 12 Feb 2021 15:10:42 +0800
Message-ID: <CAGZ6i=2LfU16K7HHVOwVsHvxpL3rQtVhnabScAReqT9cY3HWyw@mail.gmail.com>
Subject: Re: [PATCH v6 3/7] usb: typec: tcpm: Determine common SVDM Version
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Hans de Goede <hdegoede@redhat.com>,
        Rob Herring <robh+dt@kernel.org>,
        Badhri Jagan Sridharan <badhri@google.com>,
        USB <linux-usb@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>
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On Fri, Feb 12, 2021 at 12:17 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Fri, Feb 05, 2021 at 11:34:11AM +0800, Kyle Tso wrote:
> > PD Spec Revision 3.0 Version 2.0 + ECNs 2020-12-10
> >   6.4.4.2.3 Structured VDM Version
> >   "The Structured VDM Version field of the Discover Identity Command
> >   sent and received during VDM discovery Shall be used to determine the
> >   lowest common Structured VDM Version supported by the Port Partners or
> >   Cable Plug and Shall continue to operate using this Specification
> >   Revision until they are Detached."
> >
> > Also clear the fields newly defined in SVDM version 2.0 if the
> > negotiated SVDM version is 1.0.
> >
> > Signed-off-by: Kyle Tso <kyletso@google.com>
> > ---
> > Changes since v5:
> > - follow the changes of "usb: typec: Manage SVDM version"
> > - remove the "reset to default". Now the default SVDM version will be
> >   set when calling to typec_register_partner
> >
> >  drivers/usb/typec/tcpm/tcpm.c | 71 ++++++++++++++++++++++++++++++-----
> >  1 file changed, 61 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index 9aadb1e1bec5..b45cd191a8a4 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -1475,8 +1475,10 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> >                       const u32 *p, int cnt, u32 *response,
> >                       enum adev_actions *adev_action)
> >  {
> > +     struct typec_port *typec = port->typec_port;
> >       struct typec_altmode *pdev;
> >       struct pd_mode_data *modep;
> > +     int svdm_version;
> >       int rlen = 0;
> >       int cmd_type;
> >       int cmd;
> > @@ -1493,6 +1495,10 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> >       pdev = typec_match_altmode(port->partner_altmode, ALTMODE_DISCOVERY_MAX,
> >                                  PD_VDO_VID(p[0]), PD_VDO_OPOS(p[0]));
> >
> > +     svdm_version = typec_get_negotiated_svdm_version(typec);
> > +     if (svdm_version < 0)
> > +             return 0;
> > +
> >       switch (cmd_type) {
> >       case CMDT_INIT:
> >               switch (cmd) {
> > @@ -1500,10 +1506,22 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> >                       if (PD_VDO_VID(p[0]) != USB_SID_PD)
> >                               break;
> >
> > +                     if (PD_VDO_SVDM_VER(p[0]) < svdm_version)
> > +                             typec_partner_set_svdm_version(port->partner,
> > +                                                            PD_VDO_SVDM_VER(p[0]));
> >                       /* 6.4.4.3.1: Only respond as UFP (device) */
> >                       if (port->data_role == TYPEC_DEVICE &&
> >                           port->nr_snk_vdo) {
> > -                             for (i = 0; i <  port->nr_snk_vdo; i++)
> > +                             /*
> > +                              * Product Type DFP and Connector Type are not defined in SVDM
> > +                              * version 1.0 and shall be set to zero.
> > +                              */
> > +                             if (typec_get_negotiated_svdm_version(typec) < SVDM_VER_2_0)
>
> Why not
>                                 if (svdm_version)
> ?
>

The "svdm_version" at this line is the cached value of
"partner->svdm_version" at the time from below lines.
In the case of the first calling to "tcpm_pd_svdm", this value is the
default value set when "typec_register_partner" is called.

>>>>>>>>>>>>>
       pdev = typec_match_altmode(port->partner_altmode, ALTMODE_DISCOVERY_MAX,
                                  PD_VDO_VID(p[0]), PD_VDO_OPOS(p[0]));

+     svdm_version = typec_get_negotiated_svdm_version(typec);
+     if (svdm_version < 0)
+             return 0;
<<<<<<<<<<<<<

"partner->svdm_version" is updated afterward If someone calls
"typec_partner_set_svdm_version" like these lines:
>>>>>>>>>>>>>
+                     if (PD_VDO_SVDM_VER(p[0]) < svdm_version)
+                             typec_partner_set_svdm_version(port->partner,
+
PD_VDO_SVDM_VER(p[0]));
<<<<<<<<<<<<<

However, this won't update the local variable "svdm_version". That's
why we need to get the value of "partner->svdm_version" again.
Unless every time the local variable "svdm_version" is updated when
"typec_partner_set_svdm_version" is called.


> > +                                     response[1] = port->snk_vdo[0] & ~IDH_DFP_MASK
> > +                                                   & ~IDH_CONN_MASK;
> > +                             else
> > +                                     response[1] = port->snk_vdo[0];
> > +                             for (i = 1; i <  port->nr_snk_vdo; i++)
> >                                       response[i + 1] = port->snk_vdo[i];
> >                               rlen = port->nr_snk_vdo + 1;
> >                       }
> > @@ -1532,6 +1550,8 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> >                       response[0] = p[0] | VDO_CMDT(CMDT_RSP_BUSY);
> >                       rlen = 1;
> >               }
> > +             response[0] = (response[0] & ~VDO_SVDM_VERS_MASK) |
> > +                           (VDO_SVDM_VERS(typec_get_negotiated_svdm_version(typec)));
>
> Unnecessary ( ) around VDO_SVDM_VERS. Also, why not svdm_version ?
>
> >               break;
> >       case CMDT_RSP_ACK:
> >               /* silently drop message if we are not connected */
> > @@ -1542,19 +1562,22 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> >
> >               switch (cmd) {
> >               case CMD_DISCOVER_IDENT:
> > +                     if (PD_VDO_SVDM_VER(p[0]) < svdm_version)
> > +                             typec_partner_set_svdm_version(port->partner,
> > +                                                            PD_VDO_SVDM_VER(p[0]));
> >                       /* 6.4.4.3.1 */
> >                       svdm_consume_identity(port, p, cnt);
> > -                     response[0] = VDO(USB_SID_PD, 1, SVDM_VER_1_0, CMD_DISCOVER_SVID);
> > +                     response[0] = VDO(USB_SID_PD, 1, typec_get_negotiated_svdm_version(typec),
>
> Guess I am a bit confused about the use of svdm_version vs.
> typec_get_negotiated_svdm_version(typec). Is there some rationale
> for using one vs. the other ?
>

The local variable "svdm_version" is get at the beginning of this function.
It cannot be trusted if someone calls "typec_partner_set_svdm_version"
before you use the local variable.
Unless, again,  it is updated everytime the
"typec_partner_set_svdm_version" is called.


> > +                                       CMD_DISCOVER_SVID);
> >                       rlen = 1;
> >                       break;
> >               case CMD_DISCOVER_SVID:
> >                       /* 6.4.4.3.2 */
> >                       if (svdm_consume_svids(port, p, cnt)) {
> > -                             response[0] = VDO(USB_SID_PD, 1, SVDM_VER_1_0,
> > -                                               CMD_DISCOVER_SVID);
> > +                             response[0] = VDO(USB_SID_PD, 1, svdm_version, CMD_DISCOVER_SVID);
> >                               rlen = 1;
> >                       } else if (modep->nsvids && supports_modal(port)) {
> > -                             response[0] = VDO(modep->svids[0], 1, SVDM_VER_1_0,
> > +                             response[0] = VDO(modep->svids[0], 1, svdm_version,
> >                                                 CMD_DISCOVER_MODES);
> >                               rlen = 1;
> >                       }
> > @@ -1565,7 +1588,7 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> >                       modep->svid_index++;
> >                       if (modep->svid_index < modep->nsvids) {
> >                               u16 svid = modep->svids[modep->svid_index];
> > -                             response[0] = VDO(svid, 1, SVDM_VER_1_0, CMD_DISCOVER_MODES);
> > +                             response[0] = VDO(svid, 1, svdm_version, CMD_DISCOVER_MODES);
> >                               rlen = 1;
> >                       } else {
> >                               tcpm_register_partner_altmodes(port);
> > @@ -1592,6 +1615,8 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> >                       /* Unrecognized SVDM */
> >                       response[0] = p[0] | VDO_CMDT(CMDT_RSP_NAK);
> >                       rlen = 1;
> > +                     response[0] = (response[0] & ~VDO_SVDM_VERS_MASK) |
> > +                                   (VDO_SVDM_VERS(svdm_version));
> >                       break;
> >               }
> >               break;
> > @@ -1611,6 +1636,8 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> >                       /* Unrecognized SVDM */
> >                       response[0] = p[0] | VDO_CMDT(CMDT_RSP_NAK);
> >                       rlen = 1;
> > +                     response[0] = (response[0] & ~VDO_SVDM_VERS_MASK) |
> > +                                   (VDO_SVDM_VERS(svdm_version));
> >                       break;
> >               }
> >               port->vdm_sm_running = false;
> > @@ -1618,6 +1645,8 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
> >       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;
> >       }
> > @@ -1695,7 +1724,13 @@ static void tcpm_handle_vdm_request(struct tcpm_port *port,
> >                       break;
> >               case ADEV_QUEUE_VDM_SEND_EXIT_MODE_ON_FAIL:
> >                       if (typec_altmode_vdm(adev, p[0], &p[1], cnt)) {
> > -                             response[0] = VDO(adev->svid, 1, SVDM_VER_1_0, CMD_EXIT_MODE);
> > +                             int svdm_version = typec_get_negotiated_svdm_version(
> > +                                                                     port->typec_port);
> > +                             if (svdm_version < 0)
> > +                                     break;
> > +
> > +                             response[0] = VDO(adev->svid, 1, svdm_version,
> > +                                               CMD_EXIT_MODE);
> >                               response[0] |= VDO_OPOS(adev->mode);
> >                               rlen = 1;
> >                       }
> > @@ -1722,14 +1757,19 @@ static void tcpm_handle_vdm_request(struct tcpm_port *port,
> >  static void tcpm_send_vdm(struct tcpm_port *port, u32 vid, int cmd,
> >                         const u32 *data, int count)
> >  {
> > +     int svdm_version = typec_get_negotiated_svdm_version(port->typec_port);
> >       u32 header;
> >
> > +     if (svdm_version < 0)
> > +             return;
> > +
> >       if (WARN_ON(count > VDO_MAX_SIZE - 1))
> >               count = VDO_MAX_SIZE - 1;
> >
> >       /* set VDM header with VID & CMD */
> >       header = VDO(vid, ((vid & USB_SID_PD) == USB_SID_PD) ?
> > -                     1 : (PD_VDO_CMD(cmd) <= CMD_ATTENTION), SVDM_VER_1_0, cmd);
> > +                     1 : (PD_VDO_CMD(cmd) <= CMD_ATTENTION),
> > +                     svdm_version, cmd);
> >       tcpm_queue_vdm(port, header, data, count);
> >  }
> >
> > @@ -2022,9 +2062,14 @@ static int tcpm_validate_caps(struct tcpm_port *port, const u32 *pdo,
> >  static int tcpm_altmode_enter(struct typec_altmode *altmode, u32 *vdo)
> >  {
> >       struct tcpm_port *port = typec_altmode_get_drvdata(altmode);
> > +     int svdm_version;
> >       u32 header;
> >
> > -     header = VDO(altmode->svid, vdo ? 2 : 1, SVDM_VER_1_0, CMD_ENTER_MODE);
> > +     svdm_version = typec_get_negotiated_svdm_version(port->typec_port);
> > +     if (svdm_version < 0)
> > +             return svdm_version;
> > +
> > +     header = VDO(altmode->svid, vdo ? 2 : 1, svdm_version, CMD_ENTER_MODE);
> >       header |= VDO_OPOS(altmode->mode);
> >
> >       tcpm_queue_vdm_unlocked(port, header, vdo, vdo ? 1 : 0);
> > @@ -2034,9 +2079,14 @@ static int tcpm_altmode_enter(struct typec_altmode *altmode, u32 *vdo)
> >  static int tcpm_altmode_exit(struct typec_altmode *altmode)
> >  {
> >       struct tcpm_port *port = typec_altmode_get_drvdata(altmode);
> > +     int svdm_version;
> >       u32 header;
> >
> > -     header = VDO(altmode->svid, 1, SVDM_VER_1_0, CMD_EXIT_MODE);
> > +     svdm_version = typec_get_negotiated_svdm_version(port->typec_port);
> > +     if (svdm_version < 0)
> > +             return svdm_version;
> > +
> > +     header = VDO(altmode->svid, 1, svdm_version, CMD_EXIT_MODE);
> >       header |= VDO_OPOS(altmode->mode);
> >
> >       tcpm_queue_vdm_unlocked(port, header, NULL, 0);
> > @@ -5977,6 +6027,7 @@ struct tcpm_port *tcpm_register_port(struct device *dev, struct tcpc_dev *tcpc)
> >       port->typec_caps.fwnode = tcpc->fwnode;
> >       port->typec_caps.revision = 0x0120;     /* Type-C spec release 1.2 */
> >       port->typec_caps.pd_revision = 0x0300;  /* USB-PD spec release 3.0 */
> > +     port->typec_caps.svdm_version = SVDM_VER_2_0;
> >       port->typec_caps.driver_data = port;
> >       port->typec_caps.ops = &tcpm_ops;
> >       port->typec_caps.orientation_aware = 1;
> > --
> > 2.30.0.365.g02bc693789-goog
> >

thanks,
Kyle