Hi Alexandre,
> On 03/04/2019 16:52:45+0200, Flavio Suligoi wrote:
> > 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";
> > };
> > };
> >
>
> So I'm curious, how do you then use that signal? I have a (not yet sent)
> series adding alarm support for the pcf2127. The issue having BLIE is
> that then this will prevent the alarm to work properly.
>
> So my guess is that you have nINT connected to an LED or something that
> the user can see?
>
I'm working on our custom embedded board with an NXP i.MX7D,
developed here, in Asem (www.asem.it).
The nINT pin is connected to a GPIO of the MX7 and then
used by an applicative sw, to generate an alarm for the user.
> > Signed-off-by: Flavio Suligoi <f.suligoi@xxxxxxx>
> > ---
> > 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);
>
> This has to use regmap_update_bits because this also has to work on spi.
> (I don't know where you get the client pointer from anyway).
>
> > + 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
> >
>
> --
> Alexandre Belloni, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
Flavio Suligoi
