1Intersil ISL12057 I2C RTC/Alarm chip
2
3ISL12057 is a trivial I2C device (it has simple device tree bindings,
4consisting of a compatible field, an address and possibly an interrupt
5line).
6
7Nonetheless, it also supports an option boolean property
8("isil,irq2-can-wakeup-machine") to handle the specific use-case found
9on at least three in-tree users of the chip (NETGEAR ReadyNAS 102, 104
10and 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
12to the SoC but to a PMIC. It allows the device to be powered up when
13RTC alarm rings. In order to mark the device has a wakeup source and
14get access to the 'wakealarm' sysfs entry, this specific property can
15be set when the IRQ#2 pin of the chip is not connected to the SoC but
16can wake up the device.
17
18Required properties supported by the device:
19
20 - "compatible": must be "isil,isl12057"
21 - "reg": I2C bus address of the device
22
23Optional properties:
24
25 - "isil,irq2-can-wakeup-machine": mark the chip as a wakeup source,
26   independently of the availability of an IRQ line connected to the
27   SoC.
28
29 - "interrupt-parent", "interrupts": for passing the interrupt line
30   of the SoC connected to IRQ#2 of the RTC chip.
31
32
33Example isl12057 node without IRQ#2 pin connected (no alarm support):
34
35	isl12057: isl12057@68 {
36		compatible = "isil,isl12057";
37		reg = <0x68>;
38	};
39
40
41Example isl12057 node with IRQ#2 pin connected to main SoC via MPP6 (note
42that the pinctrl-related properties below are given for completeness and
43may not be required or may be different depending on your system or
44SoC, and the main function of the MPP used as IRQ line, i.e.
45"interrupt-parent" and "interrupts" are usually sufficient):
46
47		    pinctrl {
48				...
49
50				rtc_alarm_pin: rtc_alarm_pin {
51					marvell,pins = "mpp6";
52					marvell,function = "gpio";
53				};
54
55				...
56
57		    };
58
59	...
60
61	isl12057: isl12057@68 {
62		compatible = "isil,isl12057";
63		reg = <0x68>;
64		pinctrl-0 = <&rtc_alarm_pin>;
65		pinctrl-names = "default";
66		interrupt-parent = <&gpio0>;
67		interrupts = <6 IRQ_TYPE_EDGE_FALLING>;
68	};
69
70
71Example isl12057 node without IRQ#2 pin connected to the SoC but to a
72PMIC, allowing the device to be started based on configured alarm:
73
74	isl12057: isl12057@68 {
75		compatible = "isil,isl12057";
76		reg = <0x68>;
77		isil,irq2-can-wakeup-machine;
78	};
79