The pcf2127 has an automatic battery-low detection function.
In case of battery-low event, an interrupt generation through
the pin INTn (active low) can be enabled, setting the flag BLIE
in the register Control_3.
This function is activated by the "battery-low-hw-alarm" DT property.
Example of use for an NXP i.MX7D board:
&i2c3 {
clock-frequency = <100000>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_i2c3>;
status = "okay";
pcf2127@51 {
compatible = "nxp,pcf2127";
reg = <0x51>;
battery-low-hw-alarm;
status = "okay";
};
};
Signed-off-by: Flavio Suligoi <f.suli...@asem.it>
---
drivers/rtc/rtc-pcf2127.c | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
index 7cb786d..e3805c8 100644
--- a/drivers/rtc/rtc-pcf2127.c
+++ b/drivers/rtc/rtc-pcf2127.c
@@ -228,6 +228,10 @@ static int pcf2127_probe(struct device *dev, struct regmap
*regmap,
const char *name, bool has_nvmem)
{
struct pcf2127 *pcf2127;
+ struct device_node *np;
+ struct i2c_client *client = to_i2c_client(dev);
+ unsigned char buf[2];
+ int err;
int ret = 0;
dev_dbg(dev, "%s\n", __func__);
@@ -245,6 +249,35 @@ static int pcf2127_probe(struct device *dev, struct regmap
*regmap,
if (IS_ERR(pcf2127->rtc))
return PTR_ERR(pcf2127->rtc);
+ /*
+ * The pcf2127 has an automatic battery-low detection function.
+ *
+ * In case of battery-low event, an interrupt generation through
+ * the pin INTn (active low) can be enabled, setting the flag BLIE
+ * in the register Control_3.
+ */
+ np = of_node_get(dev->of_node);
+ if (!np) {
+ dev_err(dev, "failed to find the RTC pcf2127 node\n");
+ return -ENOENT;
+ }
+ if (of_get_property(np, "battery-low-hw-alarm", NULL)) {
+ dev_info(dev, "enable battery-low hw alarm on INTn pin\n");
+
+ /*
+ * Set BLIE bit in register Control_3 (override is possible
+ * because this register is fully zero after reset)
+ */
+ buf[0] = PCF2127_REG_CTRL3;
+ buf[1] = 0x01;
+ /* write register's data */
+ err = i2c_master_send(client, buf, 2);
+ if (err != 2) {
+ dev_err(dev, "%s: err=%d", __func__, err);
+ return -EIO;
+ }
+ }
+
if (has_nvmem) {
struct nvmem_config nvmem_cfg = {
.priv = pcf2127,
--
2.7.4
