Re: [PATCH v2 2/2] usb: typec: tcpm: Support non-PD mode

On Wed, Jul 28, 2021 at 6:46 AM Guenter Roeck [off-list ref] wrote:

On 7/27/21 8:13 AM, Kyle Tso wrote:

quoted

Even if the Type-C controller supports PD, it is doable to disable PD
capabilities with the current state machine in TCPM. Without enabling RX
in low-level drivers and with skipping the power negotiation, the port
is eligible to be a non-PD Type-C port. Use new flags whose values are
populated from the device tree to decide the port PD capability. Adding
"pd-supported" property in device tree indicates that the port supports
PD. If "pd-supported" is not found, "typec-power-opmode" shall be added
to specify the advertised Rp value if the port supports SRC role.

Signed-off-by: Kyle Tso <redacted>
---
changes since v1:
- Revised the patch to use dt properties
- Added back the checks of callbacks set_pd_rx and pd_transmit
- Added src_rp to indicate which Rp value should be used in SRC. This
   variable is derived from dt property "typec-power-opmode"

  drivers/usb/typec/tcpm/tcpm.c | 108 +++++++++++++++++++++++++---------
  1 file changed, 79 insertions(+), 29 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 5b22a1c931a9..4cf77c787f54 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c

@@ -316,6 +316,7 @@ struct tcpm_port {
      struct typec_partner *partner;

      enum typec_cc_status cc_req;
+     enum typec_cc_status src_rp;    /* work only if pd_supported == false */

      enum typec_cc_status cc1;
      enum typec_cc_status cc2;

@@ -323,6 +324,7 @@ struct tcpm_port {

      bool attached;
      bool connected;
+     bool pd_supported;
      enum typec_port_type port_type;

      /*

@@ -804,6 +806,7 @@ static void tcpm_apply_rc(struct tcpm_port *port)
      }
  }

+
  /*
   * Determine RP value to set based on maximum current supported
   * by a port if configured as source.

@@ -815,6 +818,9 @@ static enum typec_cc_status tcpm_rp_cc(struct tcpm_port *port)
      int nr_pdo = port->nr_src_pdo;
      int i;

+     if (!port->pd_supported)
+             return port->src_rp;
+
      /*
       * Search for first entry with matching voltage.
       * It should report the maximum supported current.

@@ -3568,9 +3574,11 @@ static int tcpm_src_attach(struct tcpm_port *port)
      if (ret < 0)
              return ret;

-     ret = port->tcpc->set_pd_rx(port->tcpc, true);
-     if (ret < 0)
-             goto out_disable_mux;
+     if (port->pd_supported) {
+             ret = port->tcpc->set_pd_rx(port->tcpc, true);
+             if (ret < 0)
+                     goto out_disable_mux;
+     }

      /*
       * USB Type-C specification, version 1.2,

@@ -3600,7 +3608,8 @@ static int tcpm_src_attach(struct tcpm_port *port)
  out_disable_vconn:
      tcpm_set_vconn(port, false);
  out_disable_pd:
-     port->tcpc->set_pd_rx(port->tcpc, false);
+     if (port->pd_supported)
+             port->tcpc->set_pd_rx(port->tcpc, false);
  out_disable_mux:
      tcpm_mux_set(port, TYPEC_STATE_SAFE, USB_ROLE_NONE,
                   TYPEC_ORIENTATION_NONE);

@@ -3804,6 +3813,20 @@ static enum typec_pwr_opmode tcpm_get_pwr_opmode(enum typec_cc_status cc)
      }
  }

+static enum typec_cc_status tcpm_pwr_opmode_to_rp(enum typec_pwr_opmode opmode)
+{
+     switch (opmode) {
+     case TYPEC_PWR_MODE_USB:
+             return TYPEC_CC_RP_DEF;
+     case TYPEC_PWR_MODE_1_5A:
+             return TYPEC_CC_RP_1_5;
+     case TYPEC_PWR_MODE_3_0A:
+     case TYPEC_PWR_MODE_PD:
+     default:
+             return TYPEC_CC_RP_3_0;
+     }
+}
+
  static void run_state_machine(struct tcpm_port *port)
  {
      int ret;

@@ -3914,6 +3937,10 @@ static void run_state_machine(struct tcpm_port *port)
              if (port->ams == POWER_ROLE_SWAP ||
                  port->ams == FAST_ROLE_SWAP)
                      tcpm_ams_finish(port);
+             if (!port->pd_supported) {
+                     tcpm_set_state(port, SRC_READY, 0);
+                     break;
+             }
              port->upcoming_state = SRC_SEND_CAPABILITIES;
              tcpm_ams_start(port, POWER_NEGOTIATION);
              break;

@@ -4161,7 +4188,10 @@ static void run_state_machine(struct tcpm_port *port)
                              current_lim = PD_P_SNK_STDBY_MW / 5;
                      tcpm_set_current_limit(port, current_lim, 5000);
                      tcpm_set_charge(port, true);
-                     tcpm_set_state(port, SNK_WAIT_CAPABILITIES, 0);
+                     if (!port->pd_supported)
+                             tcpm_set_state(port, SNK_READY, 0);
+                     else
+                             tcpm_set_state(port, SNK_WAIT_CAPABILITIES, 0);
                      break;
              }
              /*

@@ -4389,7 +4419,8 @@ static void run_state_machine(struct tcpm_port *port)
              tcpm_set_vbus(port, true);
              if (port->ams == HARD_RESET)
                      tcpm_ams_finish(port);
-             port->tcpc->set_pd_rx(port->tcpc, true);
+             if (port->pd_supported)
+                     port->tcpc->set_pd_rx(port->tcpc, true);
              tcpm_set_attached_state(port, true);
              tcpm_set_state(port, SRC_UNATTACHED, PD_T_PS_SOURCE_ON);
              break;

@@ -5898,6 +5929,7 @@ EXPORT_SYMBOL_GPL(tcpm_tcpc_reset);
  static int tcpm_fw_get_caps(struct tcpm_port *port,
                          struct fwnode_handle *fwnode)
  {
+     const char *opmode_str;
      const char *cap_str;
      int ret;
      u32 mw, frs_current;

@@ -5932,22 +5964,36 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
              return ret;
      port->typec_caps.type = ret;
      port->port_type = port->typec_caps.type;
+     port->pd_supported = fwnode_property_read_bool(fwnode, "pd-supported");

As mentioned in the other patch, I think this needs to be negated.
Not the variable itself, but the meaning of the property.

Makes sense. I will send another patch.

quoted

      port->slow_charger_loop = fwnode_property_read_bool(fwnode, "slow-charger-loop");

It might make sense to move the properties needed with !pd_supported to here
and return immediately after they are read. This would reduce the number of
required changes and avoid trying to read irrelevant properties.
Something like

        if (port->port_type != TYPEC_PORT_SRC)
                port->self_powered = fwnode_property_read_bool(fwnode, "self-powered");

        if (!port->pd_supported)
                return 0;

I will try to modify the flow control as well.

thanks,
Kyle

quoted

      if (port->port_type == TYPEC_PORT_SNK)
              goto sink;

      /* Get source pdos */
-     ret = fwnode_property_count_u32(fwnode, "source-pdos");
-     if (ret <= 0)
-             return -EINVAL;
+     if (port->pd_supported) {
+             ret = fwnode_property_count_u32(fwnode, "source-pdos");
+             if (ret <= 0)
+                     return -EINVAL;

-     port->nr_src_pdo = min(ret, PDO_MAX_OBJECTS);
-     ret = fwnode_property_read_u32_array(fwnode, "source-pdos",
-                                          port->src_pdo, port->nr_src_pdo);
-     if ((ret < 0) || tcpm_validate_caps(port, port->src_pdo,
-                                         port->nr_src_pdo))
-             return -EINVAL;
+             port->nr_src_pdo = min(ret, PDO_MAX_OBJECTS);
+             ret = fwnode_property_read_u32_array(fwnode, "source-pdos",
+                                                  port->src_pdo, port->nr_src_pdo);
+             if ((ret < 0) || tcpm_validate_caps(port, port->src_pdo,
+                                                 port->nr_src_pdo))
+                     return -EINVAL;
+     } else {
+             port->nr_src_pdo = 0;
+             ret = fwnode_property_read_string(fwnode, "typec-power-opmode", &opmode_str);
+             if (ret == 0) {
+                     ret = typec_find_pwr_opmode(opmode_str);
+                     if (ret < 0)
+                             return ret;
+                     port->src_rp = tcpm_pwr_opmode_to_rp(ret);
+             } else {
+                     return ret;
+             }
+     }

      if (port->port_type == TYPEC_PORT_SRC)
              return 0;

@@ -5962,25 +6008,29 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
              return -EINVAL;
  sink:
      /* Get sink pdos */
-     ret = fwnode_property_count_u32(fwnode, "sink-pdos");
-     if (ret <= 0)
-             return -EINVAL;
+     if (port->pd_supported) {
+             ret = fwnode_property_count_u32(fwnode, "sink-pdos");
+             if (ret <= 0)
+                     return -EINVAL;

-     port->nr_snk_pdo = min(ret, PDO_MAX_OBJECTS);
-     ret = fwnode_property_read_u32_array(fwnode, "sink-pdos",
-                                          port->snk_pdo, port->nr_snk_pdo);
-     if ((ret < 0) || tcpm_validate_caps(port, port->snk_pdo,
-                                         port->nr_snk_pdo))
-             return -EINVAL;
+             port->nr_snk_pdo = min(ret, PDO_MAX_OBJECTS);
+             ret = fwnode_property_read_u32_array(fwnode, "sink-pdos",
+                                                  port->snk_pdo, port->nr_snk_pdo);
+             if ((ret < 0) || tcpm_validate_caps(port, port->snk_pdo,
+                                                 port->nr_snk_pdo))
+                     return -EINVAL;

-     if (fwnode_property_read_u32(fwnode, "op-sink-microwatt", &mw) < 0)
-             return -EINVAL;
-     port->operating_snk_mw = mw / 1000;
+             if (fwnode_property_read_u32(fwnode, "op-sink-microwatt", &mw) < 0)
+                     return -EINVAL;
+             port->operating_snk_mw = mw / 1000;
+     } else {
+             port->nr_snk_pdo = 0;
+     }

      port->self_powered = fwnode_property_read_bool(fwnode, "self-powered");

-     /* FRS can only be supported byb DRP ports */
-     if (port->port_type == TYPEC_PORT_DRP) {
+     /* FRS can only be supported by DRP ports */
+     if (port->port_type == TYPEC_PORT_DRP && port->pd_supported) {
              ret = fwnode_property_read_u32(fwnode, "new-source-frs-typec-current",
                                             &frs_current);
              if (ret >= 0 && frs_current <= FRS_5V_3A)