[PATCH v4 1/2] power: supply: bq24735: add watchdog timer delay support

[Bruno Meneguele <bruno.meneguele@smartgreen.net>]

The BQ24735 charger allows the user to set the watchdog timer delay between
two consecutives ChargeCurrent or ChargeVoltage command writes, if the IC
doesn't receive any command before the timeout happens, the charge is turned
off.

This patch adds the support to the user to change the default/POR value with
four discrete values:

  0 - disabled
  1 - enabled, 44 sec
  2 - enabled, 88 sec
  3 - enabled, 175 sec (default at POR)

These are the options supported in the ChargeOptions register bits 13&14.

Also, this patch make one additional check when poll-interval is set by the
user: if the interval set is greater than the WDT timeout it'll fail during
the probe stage, preventing the user to set non-compatible values between
the two options.

Signed-off-by: Bruno Meneguele <bruno.meneguele@smartgreen.net>
---
Changelog:
  v3 - check wdt_timeout for the maximum and minimum available values 

 drivers/power/supply/bq24735-charger.c | 54 ++++++++++++++++++++++++++
 include/linux/power/bq24735-charger.h  |  1 +
 2 files changed, 55 insertions(+)

diff --git a/drivers/power/supply/bq24735-charger.c b/drivers/power/supply/bq24735-charger.c
index 3ce36d09c017..7e8d0c23df9a 100644
--- a/drivers/power/supply/bq24735-charger.c
+++ b/drivers/power/supply/bq24735-charger.c
@@ -45,6 +45,8 @@
 /* ChargeOptions bits of interest */
 #define BQ24735_CHARGE_OPT_CHG_DISABLE	(1 << 0)
 #define BQ24735_CHARGE_OPT_AC_PRESENT	(1 << 4)
+#define BQ24735_CHARGE_OPT_WDT_OFFSET	13
+#define BQ24735_CHARGE_OPT_WDT		(3 << BQ24735_CHARGE_OPT_WDT_OFFSET)
 
 struct bq24735 {
 	struct power_supply		*charger;
@@ -156,6 +158,20 @@ static int bq24735_config_charger(struct bq24735 *charger)
 		}
 	}
 
+	if (pdata->wdt_timeout >= 0 && pdata->wdt_timeout <= 3) {
+		value = pdata->wdt_timeout;
+
+		ret = bq24735_update_word(charger->client, BQ24735_CHARGE_OPT,
+					  BQ24735_CHARGE_OPT_WDT,
+					  (value << BQ24735_CHARGE_OPT_WDT_OFFSET));
+		if (ret < 0) {
+			dev_err(&charger->client->dev,
+				"Failed to write watchdog timer: %d\n",
+				ret);
+			return ret;
+		}
+	}
+
 	return 0;
 }
 
@@ -347,6 +363,23 @@ static struct bq24735_platform *bq24735_parse_dt_data(struct i2c_client *client)
 	if (!ret)
 		pdata->input_current = val;
 
+	ret = of_property_read_u32(np, "ti,wdt-timeout", &val);
+	if (!ret) {
+		if (val >= 0 && val <= 3) {
+			pdata->wdt_timeout = val;
+		} else {
+			dev_warn(&client->dev,
+				 "Invalid value for ti,wdt-timeout: %d",
+				 val);
+		}
+	} else {
+		/* Since 0 is a valid value (disabled), set something
+		 * greater than the maximum limit accepted from the user to
+		 * represent the "no change" state. */
+		pdata->wdt_timeout = 4;
+	}
+
+
 	pdata->ext_control = of_property_read_bool(np, "ti,external-control");
 
 	return pdata;
@@ -476,6 +509,27 @@ static int bq24735_charger_probe(struct i2c_client *client,
 			return 0;
 		if (!charger->poll_interval)
 			return 0;
+		if (charger->pdata->wdt_timeout > 0) {
+			int wdt_ms;
+
+			switch (charger->pdata->wdt_timeout) {
+			case 1:
+				wdt_ms = 44000;
+				break;
+			case 2:
+				wdt_ms = 88000;
+				break;
+			case 3:
+				wdt_ms = 175000;
+				break;
+			}
+
+			if (charger->poll_interval > wdt_ms) {
+				dev_err(&client->dev,
+					"Poll interval greater than WDT timeout\n");
+				return -EINVAL;
+			}
+		}
 
 		ret = devm_delayed_work_autocancel(&client->dev, &charger->poll,
 						   bq24735_poll);
diff --git a/include/linux/power/bq24735-charger.h b/include/linux/power/bq24735-charger.h
index 321dd009ce66..ce5a030ca111 100644
--- a/include/linux/power/bq24735-charger.h
+++ b/include/linux/power/bq24735-charger.h
@@ -12,6 +12,7 @@ struct bq24735_platform {
 	uint32_t charge_current;
 	uint32_t charge_voltage;
 	uint32_t input_current;
+	uint32_t wdt_timeout;
 
 	const char *name;
 
-- 
2.31.1