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

Guenter Roeck
2021-07-27T22:47:01Z

On 7/27/21 8:13 AM, Kyle Tso wrote:
> 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 <kyletso@google.com>
> ---
> 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.

> 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;

> 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)
>