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

[Amit Sunil Dhamne via B4 Relay <devnull+amitsd.google.com@kernel.org>]

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>
---
 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