Re: [PATCH v2 3/3] usb: typec: tcpci_maxim: implement get_current_limit

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Sun, Oct 04, 2026 at 03:41:01AM +0000, Amit Sunil Dhamne via B4 Relay wrote:
> From: Amit Sunil Dhamne <amitsd@google.com>
> 
> Implement tcpci_data::get_current_limit for tcpci_maxim driver to report
> a value of 500 mA unconditionally. This is the max current a configured
> USB 2.0 device may draw per the USB Type-C Cable and Connector
> Specification r2.2, Sec. 4.6.2.1. This helps set a current limit and
> thus enable charging for the cases when a port is connected to a non-PD
> Type-C port partner advertising Rp-def. This is until a mechanism for
> USB core to communicate the current limit to the TCPC driver is
> implemented.
> 
> Assisted-by: LLM
> Signed-off-by: Amit Sunil Dhamne <amitsd@google.com>
> Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>

Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
>  drivers/usb/typec/tcpm/tcpci_maxim_core.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpci_maxim_core.c b/drivers/usb/typec/tcpm/tcpci_maxim_core.c
> index 998693a61839..e6f825931ba0 100644
> --- a/drivers/usb/typec/tcpm/tcpci_maxim_core.c
> +++ b/drivers/usb/typec/tcpm/tcpci_maxim_core.c
> @@ -482,6 +482,20 @@ static bool max_tcpci_attempt_vconn_swap_discovery(struct tcpci *tcpci, struct t
>  	return true;
>  }
>  
> +/*
> + * This callback is used by the TCPM to determine the current limit to set when
> + * Rp-def is advertised on the CC pins. The actual current limit comes from
> + * other subsystems such as the USB gadget/host stack (USB 2.0/USB 3.2) and
> + * BC1.2. As a workaround, report the USB 2.0 current limit of 500 mA to enable
> + * charging when the device is connected to a non-PD source advertising Rp-def.
> + * This can be removed once a mechanism for the USB core to communicate the
> + * current limit to this driver is implemented.
> + */
> +static int max_tcpci_get_current_limit(struct tcpci *tcpci, struct tcpci_data *tdata)
> +{
> +	return 500;
> +}
> +
>  static void max_tcpci_unregister_tcpci_port(void *tcpci)
>  {
>  	tcpci_unregister_port(tcpci);
> @@ -523,6 +537,7 @@ static int max_tcpci_probe(struct i2c_client *client)
>  	chip->data.check_contaminant = max_tcpci_check_contaminant;
>  	chip->data.cable_comm_capable = true;
>  	chip->data.attempt_vconn_swap_discovery = max_tcpci_attempt_vconn_swap_discovery;
> +	chip->data.get_current_limit = max_tcpci_get_current_limit;
>  
>  	max_tcpci_init_regs(chip);
>  	chip->tcpci = tcpci_register_port(chip->dev, &chip->data);
> 
> -- 
> 2.56.0.rc1.315.gc6ed9934b7-goog
> 

-- 
heikki