[PATCH 02/18] staging: typec: tcpm: Add extcon helper functions for USB2 current limit detect

[Hans de Goede <hdegoede@redhat.com>]

Some type-c port-controllers, such as the fusb302 port-controller, rely
on an external device doing USB2 charger-type detection.

Existing PMIC (and charger) drivers already use extcon to communicate the
detected charger-type from the PMIC (extcon) driver to the charger driver.

Rather then inventing a new API for USB2 charger-type detection
specifically for use with the tcpm code, lets simply re-use the existing
support. This will also allow re-using existing PMIC extcon drivers such
as the axp288 and Intel Whiskey Cove drivers as is on devices where these
are combined with a fusb302 (or in the future another port-controller
which relies on external USB2 charger-type detection).

This commit adds a helper function which tcpc drivers can use to easily
hook into existing PMIC extcon drivers for USB2 charger-type detection:

int tcpm_get_usb2_current_limit_extcon(struct tcpc_dev *tcpc);

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/staging/typec/tcpm.c | 40 ++++++++++++++++++++++++++++++++++++++++
 drivers/staging/typec/tcpm.h |  6 ++++++
 2 files changed, 46 insertions(+)

diff --git a/drivers/staging/typec/tcpm.c b/drivers/staging/typec/tcpm.c
index 9f5adace4309..06bb0e640bcf 100644
--- a/drivers/staging/typec/tcpm.c
+++ b/drivers/staging/typec/tcpm.c
@@ -16,6 +16,7 @@
 
 #include <linux/completion.h>
 #include <linux/debugfs.h>
+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -3532,6 +3533,45 @@ void tcpm_unregister_port(struct tcpm_port *port)
 }
 EXPORT_SYMBOL_GPL(tcpm_unregister_port);
 
+/* Generic (helper) implementations for some tcpc_dev callbacks */
+int tcpm_get_usb2_current_limit_extcon(struct tcpc_dev *tcpc)
+{
+	struct extcon_dev *extcon = tcpc->usb2_extcon;
+	int current_limit = 0;
+	unsigned long timeout;
+
+	if (!extcon)
+		return 0;
+
+	/*
+	 * USB2 Charger detection may still be in progress when we get here,
+	 * this can take upto 600ms, wait 800ms max.
+	 */
+	timeout = jiffies + msecs_to_jiffies(800);
+	do {
+		if (extcon_get_state(extcon, EXTCON_CHG_USB_SDP) == 1) {
+			current_limit = 500;
+			break;
+		}
+
+		if (extcon_get_state(extcon, EXTCON_CHG_USB_CDP) == 1 ||
+		    extcon_get_state(extcon, EXTCON_CHG_USB_ACA) == 1) {
+			current_limit = 1500;
+			break;
+		}
+
+		if (extcon_get_state(extcon, EXTCON_CHG_USB_DCP) == 1) {
+			current_limit = 2000;
+			break;
+		}
+
+		msleep(50);
+	} while (time_before(jiffies, timeout));
+
+	return current_limit;
+}
+EXPORT_SYMBOL_GPL(tcpm_get_usb2_current_limit_extcon);
+
 MODULE_AUTHOR("Guenter Roeck <groeck@chromium.org>");
 MODULE_DESCRIPTION("USB Type-C Port Manager");
 MODULE_LICENSE("GPL");
diff --git a/drivers/staging/typec/tcpm.h b/drivers/staging/typec/tcpm.h
index 01b7d89379a3..35e8c1e7dba0 100644
--- a/drivers/staging/typec/tcpm.h
+++ b/drivers/staging/typec/tcpm.h
@@ -16,6 +16,7 @@
 #define __LINUX_USB_TCPM_H
 
 #include <linux/bitops.h>
+#include <linux/extcon.h>
 #include <linux/usb/typec.h>
 #include "pd.h"
 
@@ -126,6 +127,8 @@ struct tcpc_dev {
 	int (*pd_transmit)(struct tcpc_dev *dev, enum tcpm_transmit_type type,
 			   const struct pd_message *msg);
 	struct tcpc_mux_dev *mux;
+	/* Used by tcpm_get_usb2_current_limit_extcon helpers */
+	struct extcon_dev *usb2_extcon;
 };
 
 struct tcpm_port;
@@ -151,4 +154,7 @@ void tcpm_pd_transmit_complete(struct tcpm_port *port,
 void tcpm_pd_hard_reset(struct tcpm_port *port);
 void tcpm_tcpc_reset(struct tcpm_port *port);
 
+/* Generic (helper) implementations for some tcpc_dev callbacks */
+int tcpm_get_usb2_current_limit_extcon(struct tcpc_dev *tcpc);
+
 #endif /* __LINUX_USB_TCPM_H */
-- 
2.13.3