[PATCH] rtc: rv3028: Improve trickle charger logic

Andrej Picej
2023-06-08T11:00:39Z

Property "trickle-resistor-ohms" allows us to set trickle charger
resistor. However there is no possibility to disable it afterwards.

From now on, disable trickle charger circuit in case device-tree
property "trickle-resistor-ohms" is not present. RV3029 RTC driver uses
the same trickle charger disable logic.

Additionally, lets make sure we only update internal EEPROM in case of a
change. This prevents wear due to excessive EEPROM writes on each probe.

Signed-off-by: Andrej Picej <andrej.picej@norik.com>
---
drivers/rtc/rtc-rv3028.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/rtc-rv3028.c b/drivers/rtc/rtc-rv3028.c
index ec5d7a614e2d..190507bf97d0 100644
--- a/drivers/rtc/rtc-rv3028.c
+++ b/drivers/rtc/rtc-rv3028.c
@@ -860,6 +860,7 @@ static int rv3028_probe(struct i2c_client *client)
struct rv3028_data *rv3028;
int ret, status;
u32 ohms;
+ int val_old, val;
struct nvmem_config nvmem_cfg = {
.name = "rv3028_nvram",
.word_size = 1,
@@ -937,9 +938,18 @@ static int rv3028_probe(struct i2c_client *client)
if (ret)
return ret;

+ ret = regmap_read(rv3028->regmap, RV3028_BACKUP, &val_old);
+ if (ret < 0)
+ return ret;
+
+ /* mask out only trickle charger bits */
+ val_old = val_old & (RV3028_BACKUP_TCE | RV3028_BACKUP_TCR_MASK);
+
/* setup trickle charger */
- if (!device_property_read_u32(&client->dev, "trickle-resistor-ohms",
- &ohms)) {
+ if (device_property_read_u32(&client->dev, "trickle-resistor-ohms", &ohms)) {
+ /* disable the trickle charger */
+ val = 0;
+ } else {
int i;

for (i = 0; i < ARRAY_SIZE(rv3028_trickle_resistors); i++)
@@ -947,15 +957,21 @@ static int rv3028_probe(struct i2c_client *client)
break;

if (i < ARRAY_SIZE(rv3028_trickle_resistors)) {
- ret = rv3028_update_cfg(rv3028, RV3028_BACKUP, RV3028_BACKUP_TCE |
- RV3028_BACKUP_TCR_MASK, RV3028_BACKUP_TCE | i);
- if (ret)
- return ret;
+ /* enable the trickle charger and setup its resistor accordingly */
+ val = RV3028_BACKUP_TCE | i;
} else {
dev_warn(&client->dev, "invalid trickle resistor value\n");
}
}

+ /* only update EEPROM if changes are necessary */
+ if (val_old != val) {
+ ret = rv3028_update_cfg(rv3028, RV3028_BACKUP, RV3028_BACKUP_TCE |
+ RV3028_BACKUP_TCR_MASK, val);
+ if (ret)
+ return ret;
+ }
+
ret = rtc_add_group(rv3028->rtc, &rv3028_attr_group);
if (ret)
return ret;
--
2.25.1