RTC integration with kernel

GoogleGroups
1

HI,

I’m trying to get a battery backed RTC chip to work with the Beaglebone. It works on 4.14 kernel but I am trying to do the same on 3.8 kernel and I can’t get it to appear as a device in /dev

So far I have the device tree mappings for BB-I2C1 installed. (Which is referenced as i2c-2 - a known issue that is fixed in kernel 4). This seems to be ok as I can see the device:

root@beaglebone:~# i2cdetect -r 2
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-2 using read byte commands.
I will probe address range 0x03-0x77.
Continue? [Y/n] Y
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: – -- – -- – -- – -- – -- – -- –
10: – -- – -- – -- – -- – -- – -- – -- – --
20: – -- – -- – -- – -- – -- – -- – -- – --
30: – -- – -- – -- – -- – -- – -- – -- – --
40: – -- – -- – -- – -- – -- – -- – -- – --
50: – -- – -- – -- – -- – -- – -- – -- – --
60: – -- – -- – -- – -- 68 – -- – -- – -- –
70: – -- – -- – -- – --

I mount it with:

echo ds3232 0x68 > /sys/class/i2c-adapter/i2c-2/new_device

dmesg shows:

[ 7242.287395] i2c i2c-2: new_device: Instantiated device ds3232 at 0x68

However a new device /dev/rtc1 is not created and only the rtc built into the BBB is visable.

I’n not sure what to try next… Can anyone help?

Neil

2

If memory serves you need to insmod the driver for those chips on 3.x. I forget offhand what driver covers that chip, google should easily produce that answer. Mike

3

I use the following device tree fragment to set up my battery backed DS1307. I imagine all you have to do for the 3232 is change the compatible parameter.

&i2c2 {
status = “okay”;
pinctrl-names = “default”;
pinctrl-0 = <&i2c2_pins>;

clock-frequency = <100000>;

cape_rtc0: cape_rtc0@68 {
compatible = “maxim,ds1307”;
reg = <0x68>;
};
};