1 Intersil ISL12057 I2C RTC/Alarm chip
2
3 ISL12057 is a trivial I2C device (it has simple device tree bindings,
4 consisting of a compatible field, an address and possibly an interrupt
5 line).
6
7 Nonetheless, it also supports an option boolean property
8 ("wakeup-source") to handle the specific use-case found
9 on at least three in-tree users of the chip (NETGEAR ReadyNAS 102, 104
10 and 2120 ARM-based NAS); On those devices, the IRQ#2 pin of the chip
11 (associated with the alarm supported by the driver) is not connected
12 to the SoC but to a PMIC. It allows the device to be powered up when
13 RTC alarm rings. In order to mark the device has a wakeup source and
14 get access to the 'wakealarm' sysfs entry, this specific property can
15 be set when the IRQ#2 pin of the chip is not connected to the SoC but
16 can wake up the device.
17
18 Required properties supported by the device:
19
20 - "compatible": must be "isil,isl12057"
21 - "reg": I2C bus address of the device
22
23 Optional properties:
24
25 - "wakeup-source": mark the chip as a wakeup source, independently of
26 the availability of an IRQ line connected to the SoC.
27
28
29 Example isl12057 node without IRQ#2 pin connected (no alarm support):
30
31 isl12057: isl12057@68 {
32 compatible = "isil,isl12057";
33 reg = <0x68>;
34 };
35
36
37 Example isl12057 node with IRQ#2 pin connected to main SoC via MPP6 (note
38 that the pinctrl-related properties below are given for completeness and
39 may not be required or may be different depending on your system or
40 SoC, and the main function of the MPP used as IRQ line, i.e.
41 "interrupt-parent" and "interrupts" are usually sufficient):
42
43 pinctrl {
44 ...
45
46 rtc_alarm_pin: rtc_alarm_pin {
47 marvell,pins = "mpp6";
48 marvell,function = "gpio";
49 };
50
51 ...
52
53 };
54
55 ...
56
57 isl12057: isl12057@68 {
58 compatible = "isil,isl12057";
59 reg = <0x68>;
60 pinctrl-0 = <&rtc_alarm_pin>;
61 pinctrl-names = "default";
62 interrupt-parent = <&gpio0>;
63 interrupts = <6 IRQ_TYPE_EDGE_FALLING>;
64 };
65
66
67 Example isl12057 node without IRQ#2 pin connected to the SoC but to a
68 PMIC, allowing the device to be started based on configured alarm:
69
70 isl12057: isl12057@68 {
71 compatible = "isil,isl12057";
72 reg = <0x68>;
73 wakeup-source;
74 };
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