power: bq24257: Add SW-based approach for Power Good determination

A software-based approach for determining the charger's input voltage
"Power Good" state is introduced for devices like the bq24250 which
don't have a dedicated hardware pin for that purpose. This SW-based
approach is also used for other devices (with dedicated PG pin) as a
fall back solution if that pin is not configured to be used through
"pg-gpios".

Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

diff --git a/drivers/power/bq24257_charger.c b/drivers/power/bq24257_charger.c
index 7bbff806624f538144e88d5373653e82f10aeac8..15e0e939537189906a5bcd85d2175015026a997d 100644 (file)
--- a/drivers/power/bq24257_charger.c
+++ b/drivers/power/bq24257_charger.c
@@ -359,7 +359,26 @@ static int bq24257_get_chip_state(struct bq24257_device *bq,
 
        state->fault = ret;
 
-       state->power_good = !gpiod_get_value_cansleep(bq->pg);
+       if (bq->pg)
+               state->power_good = !gpiod_get_value_cansleep(bq->pg);
+       else
+               /*
+                * If we have a chip without a dedicated power-good GPIO or
+                * some other explicit bit that would provide this information
+                * assume the power is good if there is no supply related
+                * fault - and not good otherwise. There is a possibility for
+                * other errors to mask that power in fact is not good but this
+                * is probably the best we can do here.
+                */
+               switch (state->fault) {
+               case FAULT_INPUT_OVP:
+               case FAULT_INPUT_UVLO:
+               case FAULT_INPUT_LDO_LOW:
+                       state->power_good = false;
+                       break;
+               default:
+                       state->power_good = true;
+               }
 
        return 0;
 }
@@ -651,15 +670,21 @@ static int bq24257_power_supply_init(struct bq24257_device *bq)
        return PTR_ERR_OR_ZERO(bq->charger);
 }
 
-static int bq24257_pg_gpio_probe(struct bq24257_device *bq)
+static void bq24257_pg_gpio_probe(struct bq24257_device *bq)
 {
-       bq->pg = devm_gpiod_get_index(bq->dev, BQ24257_PG_GPIO, 0, GPIOD_IN);
-       if (IS_ERR(bq->pg)) {
-               dev_err(bq->dev, "could not probe PG pin\n");
-               return PTR_ERR(bq->pg);
+       bq->pg = devm_gpiod_get_optional(bq->dev, BQ24257_PG_GPIO, GPIOD_IN);
+
+       if (PTR_ERR(bq->pg) == -EPROBE_DEFER) {
+               dev_info(bq->dev, "probe retry requested for PG pin\n");
+               return;
+       } else if (IS_ERR(bq->pg)) {
+               dev_err(bq->dev, "error probing PG pin\n");
+               bq->pg = NULL;
+               return;
        }
 
-       return 0;
+       if (bq->pg)
+               dev_dbg(bq->dev, "probed PG pin = %d\n", desc_to_gpio(bq->pg));
 }
 
 static int bq24257_fw_probe(struct bq24257_device *bq)
@@ -789,10 +814,19 @@ static int bq24257_probe(struct i2c_client *client,
                INIT_DELAYED_WORK(&bq->iilimit_setup_work,
                                  bq24257_iilimit_setup_work);
 
-       /* we can only check Power Good status by probing the PG pin */
-       ret = bq24257_pg_gpio_probe(bq);
-       if (ret < 0)
-               return ret;
+       /*
+        * The BQ24250 doesn't have a dedicated Power Good (PG) pin so let's
+        * not probe for it and instead use a SW-based approach to determine
+        * the PG state. We also use a SW-based approach for all other devices
+        * if the PG pin is either not defined or can't be probed.
+        */
+       if (bq->chip != BQ24250)
+               bq24257_pg_gpio_probe(bq);
+
+       if (PTR_ERR(bq->pg) == -EPROBE_DEFER)
+               return PTR_ERR(bq->pg);
+       else if (!bq->pg)
+               dev_info(bq->dev, "using SW-based power-good detection\n");
 
        /* reset all registers to defaults */
        ret = bq24257_field_write(bq, F_RESET, 1);