On Tue, Apr 13, 2021 at 07:39:59PM -0700, Badhri Jagan Sridharan wrote:
> When a PD charger advertising Rp-3.0 is connected to a sink port, the
> sink port current limit would 3A, during SNK_DISCOVERY, till power
> negotiation starts. Once the negotiation starts the power limit needs
> to drop down to pSnkStby(500mA @ 5V) and to negotiated current limit
> once the explicit contract is in place. Not all charging loops can ramp
> up to 3A and drop down to 500mA within tSnkStdby which is 15ms. The port
> partner might hard reset if tSnkStdby is not met.
>
> To solve this problem, this patch introduces slow-charger-loop which
> when set makes the port request PD_P_SNK_STDBY_MW upon entering
> SNK_DISCOVERY(instead of 3A or the 1.5A during SNK_DISCOVERY) and the
> actual currrent limit after RX of PD_CTRL_PSRDY for PD link or during
> SNK_READY for non-pd link.
>
> Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> Changes since V2:
> * Refactored code based on Heikki's suggestion
> ---
> drivers/usb/typec/tcpm/tcpm.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index aedc8bb9532a..2ad5e14a6867 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -459,6 +459,12 @@ struct tcpm_port {
> /* Auto vbus discharge status */
> bool auto_vbus_discharge_enabled;
>
> + /*
> + * When set, port requests PD_P_SNK_STDBY_MW upon entering SNK_DISCOVERY and
> + * the actual currrent limit after RX of PD_CTRL_PSRDY for PD link,
> + * SNK_READY for non-pd link.
> + */
> + bool slow_charger_loop;
> #ifdef CONFIG_DEBUG_FS
> struct dentry *dentry;
> struct mutex logbuffer_lock; /* log buffer access lock */
> @@ -4047,9 +4053,11 @@ static void run_state_machine(struct tcpm_port *port)
> break;
> case SNK_DISCOVERY:
> if (port->vbus_present) {
> - tcpm_set_current_limit(port,
> - tcpm_get_current_limit(port),
> - 5000);
> + u32 current_lim = tcpm_get_current_limit(port);
> +
> + if (port->slow_charger_loop || (current_lim > PD_P_SNK_STDBY_MW / 5))
> + 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);
> break;
> @@ -4161,6 +4169,8 @@ static void run_state_machine(struct tcpm_port *port)
> port->pwr_opmode = TYPEC_PWR_MODE_PD;
> }
>
> + if (!port->pd_capable && port->slow_charger_loop)
> + tcpm_set_current_limit(port, tcpm_get_current_limit(port), 5000);
> tcpm_swap_complete(port, 0);
> tcpm_typec_connect(port);
> mod_enable_frs_delayed_work(port, 0);
> @@ -5763,6 +5773,7 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
> port->typec_caps.type = ret;
> port->port_type = port->typec_caps.type;
>
> + port->slow_charger_loop = fwnode_property_read_bool(fwnode, "slow-charger-loop");
> if (port->port_type == TYPEC_PORT_SNK)
> goto sink;
>
> --
> 2.31.1.295.g9ea45b61b8-goog
thanks,
--
heikki
