staging: typec: fusb302: Export current-limit through a power_supply class dev

The fusb302 Type-C port-controller cannot control the current-limit
directly, so we need to exported the limit so that another driver
(e.g. the charger driver) can pick the limit up and configure the
system accordingly.

The power-supply subsys already provides infrastructure for this,
power-supply devices have the notion of being supplied by another
power-supply and have properties through which we can export the
current-limit.

Register a power_supply and export the current-limit through the
power_supply's current-max property.

Cc: "Yueyao (Nathan) Zhu" <yueyao@google.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 62 insertions, 3 deletions

diff --git a/drivers/staging/typec/fusb302/Kconfig b/drivers/staging/typec/fusb302/Kconfig
index fce099ff39fe..48a4f2fcee03 100644
--- a/drivers/staging/typec/fusb302/Kconfig
+++ b/drivers/staging/typec/fusb302/Kconfig
@@ -1,6 +1,6 @@
 config TYPEC_FUSB302
         tristate "Fairchild FUSB302 Type-C chip driver"
-        depends on I2C
+        depends on I2C && POWER_SUPPLY
         help
           The Fairchild FUSB302 Type-C chip driver that works with
           Type-C Port Controller Manager to provide USB PD and USB
diff --git a/drivers/staging/typec/fusb302/fusb302.c b/drivers/staging/typec/fusb302/fusb302.c
index 6f007f66d597..cf6355f59cd9 100644
--- a/drivers/staging/typec/fusb302/fusb302.c
+++ b/drivers/staging/typec/fusb302/fusb302.c
@@ -28,6 +28,7 @@
 #include <linux/of_device.h>
 #include <linux/of_gpio.h>
 #include <linux/pinctrl/consumer.h>
+#include <linux/power_supply.h>
 #include <linux/proc_fs.h>
 #include <linux/regulator/consumer.h>
 #include <linux/sched/clock.h>
@@ -108,6 +109,11 @@ struct fusb302_chip {
         /* lock for sharing chip states */
         struct mutex lock;
 
+        /* psy + psy status */
+        struct power_supply *psy;
+        u32 current_limit;
+        u32 supply_voltage;
+
         /* chip status */
         enum toggling_mode toggling_mode;
         enum src_current_status src_current_status;
@@ -876,11 +882,13 @@ static int tcpm_set_vbus(struct tcpc_dev *dev, bool on, bool charge)
                 chip->vbus_on = on;
                 fusb302_log(chip, "vbus := %s", on ? "On" : "Off");
         }
-        if (chip->charge_on == charge)
+        if (chip->charge_on == charge) {
                 fusb302_log(chip, "charge is already %s",
                             charge ? "On" : "Off");
-        else
+        } else {
                 chip->charge_on = charge;
+                power_supply_changed(chip->psy);
+        }
 
 done:
         mutex_unlock(&chip->lock);
@@ -896,6 +904,11 @@ static int tcpm_set_current_limit(struct tcpc_dev *dev, u32 max_ma, u32 mv)
         fusb302_log(chip, "current limit: %d ma, %d mv (not implemented)",
                     max_ma, mv);
 
+        chip->supply_voltage = mv;
+        chip->current_limit = max_ma;
+
+        power_supply_changed(chip->psy);
+
         return 0;
 }
 
@@ -1681,6 +1694,43 @@ done:
         return IRQ_HANDLED;
 }
 
+static int fusb302_psy_get_property(struct power_supply *psy,
+                                    enum power_supply_property psp,
+                                    union power_supply_propval *val)
+{
+        struct fusb302_chip *chip = power_supply_get_drvdata(psy);
+
+        switch (psp) {
+        case POWER_SUPPLY_PROP_ONLINE:
+                val->intval = chip->charge_on;
+                break;
+        case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+                val->intval = chip->supply_voltage * 1000; /* mV -> µV */
+                break;
+        case POWER_SUPPLY_PROP_CURRENT_MAX:
+                val->intval = chip->current_limit * 1000; /* mA -> µA */
+                break;
+        default:
+                return -ENODATA;
+        }
+
+        return 0;
+}
+
+static enum power_supply_property fusb302_psy_properties[] = {
+        POWER_SUPPLY_PROP_ONLINE,
+        POWER_SUPPLY_PROP_VOLTAGE_NOW,
+        POWER_SUPPLY_PROP_CURRENT_MAX,
+};
+
+const struct power_supply_desc fusb302_psy_desc = {
+        .name           = "fusb302-typec-source",
+        .type           = POWER_SUPPLY_TYPE_USB_TYPE_C,
+        .properties     = fusb302_psy_properties,
+        .num_properties = ARRAY_SIZE(fusb302_psy_properties),
+        .get_property   = fusb302_psy_get_property,
+};
+
 static int init_gpio(struct fusb302_chip *chip)
 {
         struct device_node *node;
@@ -1720,6 +1770,7 @@ static int fusb302_probe(struct i2c_client *client,
         struct fusb302_chip *chip;
         struct i2c_adapter *adapter;
         struct device *dev = &client->dev;
+        struct power_supply_config cfg = {};
         const char *name;
         int ret = 0;
         u32 v;
@@ -1766,6 +1817,14 @@ static int fusb302_probe(struct i2c_client *client,
                         return -EPROBE_DEFER;
         }
 
+        cfg.drv_data = chip;
+        chip->psy = devm_power_supply_register(dev, &fusb302_psy_desc, &cfg);
+        if (IS_ERR(chip->psy)) {
+                ret = PTR_ERR(chip->psy);
+                dev_err(chip->dev, "Error registering power-supply: %d\n", ret);
+                return ret;
+        }
+
         ret = fusb302_debugfs_init(chip);
         if (ret < 0)
                 return ret;