Add PMIC configurations for backup battery charger, which
is a constant voltage and constant current style charger
with a series output resistance.

The max77620 register CNFGBBC(addr: 0x04) defines the
parameters of backup battery charger. This patch adds
support for it.

Signed-off-by: Laxman Dewangan <ldewan...@nvidia.com>
Signed-off-by: Venkat Reddy Talla <vreddyta...@nvidia.com>
Signed-off-by: Mark Zhang <ma...@nvidia.com>
---
 drivers/mfd/max77620.c | 80 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)

diff --git a/drivers/mfd/max77620.c b/drivers/mfd/max77620.c
index d8ddd1a6f304..f58143103185 100644
--- a/drivers/mfd/max77620.c
+++ b/drivers/mfd/max77620.c
@@ -398,6 +398,82 @@ static int max77620_initialise_fps(struct max77620_chip 
*chip)
        return 0;
 }
 
+static int max77620_init_backup_battery_charging(struct max77620_chip *chip)
+{
+       struct device *dev = chip->dev;
+       struct device_node *np;
+       u32 pval;
+       u8 config;
+       int charging_current;
+       int charging_voltage;
+       int resistor;
+       int ret;
+
+       np = of_get_child_by_name(dev->of_node, "backup-battery");
+       if (!np) {
+               dev_info(dev, "Backup battery charging support disabled\n");
+               ret = regmap_update_bits(chip->rmap, MAX77620_REG_CNFGBBC,
+                                        MAX77620_CNFGBBC_ENABLE, 0);
+               if (ret < 0)
+                       dev_err(dev, "Failed to update CNFGBBC: %d\n", ret);
+               return ret;
+       }
+
+       ret = of_property_read_u32(np,
+                       "maxim,backup-battery-charging-current", &pval);
+       charging_current = (!ret) ? pval : 50;
+
+       ret = of_property_read_u32(np,
+                       "maxim,backup-battery-charging-voltage", &pval);
+       charging_voltage = (!ret) ? pval : 2500000;
+       charging_voltage /= 1000;
+
+       ret = of_property_read_u32(np,
+                       "maxim,backup-battery-output-resister", &pval);
+       resistor = (!ret) ? pval : 1000;
+
+       config = MAX77620_CNFGBBC_ENABLE;
+       if (charging_current <= 50)
+               config |= 0 << MAX77620_CNFGBBC_CURRENT_SHIFT;
+       else if (charging_current <= 100)
+               config |= 3 << MAX77620_CNFGBBC_CURRENT_SHIFT;
+       else if (charging_current <= 200)
+               config |= 0 << MAX77620_CNFGBBC_CURRENT_SHIFT;
+       else if (charging_current <= 400)
+               config |= 3 << MAX77620_CNFGBBC_CURRENT_SHIFT;
+       else if (charging_current <= 600)
+               config |= 1 << MAX77620_CNFGBBC_CURRENT_SHIFT;
+       else
+               config |= 2 << MAX77620_CNFGBBC_CURRENT_SHIFT;
+
+       if (charging_current > 100)
+               config |= MAX77620_CNFGBBC_LOW_CURRENT_DISABLE;
+
+       if (charging_voltage <= 2500)
+               config |= 0 << MAX77620_CNFGBBC_VOLTAGE_SHIFT;
+       else if (charging_voltage <= 3000)
+               config |= 1 << MAX77620_CNFGBBC_VOLTAGE_SHIFT;
+       else if (charging_voltage <= 3300)
+               config |= 2 << MAX77620_CNFGBBC_VOLTAGE_SHIFT;
+       else
+               config |= 3 << MAX77620_CNFGBBC_VOLTAGE_SHIFT;
+
+       if (resistor <= 100)
+               config |= 0 << MAX77620_CNFGBBC_RESISTOR_SHIFT;
+       else if (resistor <= 1000)
+               config |= 1 << MAX77620_CNFGBBC_RESISTOR_SHIFT;
+       else if (resistor <= 3000)
+               config |= 2 << MAX77620_CNFGBBC_RESISTOR_SHIFT;
+       else if (resistor <= 6000)
+               config |= 3 << MAX77620_CNFGBBC_RESISTOR_SHIFT;
+
+       ret = regmap_write(chip->rmap, MAX77620_REG_CNFGBBC, config);
+       if (ret < 0)
+               dev_err(dev, "Reg 0x%02x write failed, %d\n",
+                               MAX77620_REG_CNFGBBC, ret);
+       return ret;
+}
+
 static int max77620_read_es_version(struct max77620_chip *chip)
 {
        unsigned int val;
@@ -483,6 +559,10 @@ static int max77620_probe(struct i2c_client *client,
        if (ret < 0)
                return ret;
 
+       ret = max77620_init_backup_battery_charging(chip);
+       if (ret < 0)
+               return ret;
+
        ret =  devm_mfd_add_devices(chip->dev, PLATFORM_DEVID_NONE,
                                    mfd_cells, n_mfd_cells, NULL, 0,
                                    regmap_irq_get_domain(chip->top_irq_data));
-- 
2.19.2

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