xref: /openbmc/linux/Documentation/hwmon/jc42.rst (revision 2cf1c348)
1Kernel driver jc42
2==================
3
4Supported chips:
5
6  * Analog Devices ADT7408
7
8    Datasheets:
9
10	https://www.analog.com/static/imported-files/data_sheets/ADT7408.pdf
11
12  * Atmel AT30TS00, AT30TS002A/B, AT30TSE004A
13
14    Datasheets:
15
16	http://www.atmel.com/Images/doc8585.pdf
17
18	http://www.atmel.com/Images/doc8711.pdf
19
20	http://www.atmel.com/Images/Atmel-8852-SEEPROM-AT30TSE002A-Datasheet.pdf
21
22	http://www.atmel.com/Images/Atmel-8868-DTS-AT30TSE004A-Datasheet.pdf
23
24  * IDT TSE2002B3, TSE2002GB2, TSE2004GB2, TS3000B3, TS3000GB0, TS3000GB2,
25
26	TS3001GB2
27
28    Datasheets:
29
30	Available from IDT web site
31
32  * Maxim MAX6604
33
34    Datasheets:
35
36	http://datasheets.maxim-ic.com/en/ds/MAX6604.pdf
37
38  * Microchip MCP9804, MCP9805, MCP9808, MCP98242, MCP98243, MCP98244, MCP9843
39
40    Datasheets:
41
42	https://ww1.microchip.com/downloads/en/DeviceDoc/22203C.pdf
43
44	https://ww1.microchip.com/downloads/en/DeviceDoc/21977b.pdf
45
46	https://ww1.microchip.com/downloads/en/DeviceDoc/25095A.pdf
47
48	https://ww1.microchip.com/downloads/en/DeviceDoc/21996a.pdf
49
50	https://ww1.microchip.com/downloads/en/DeviceDoc/22153c.pdf
51
52	https://ww1.microchip.com/downloads/en/DeviceDoc/22327A.pdf
53
54  * NXP Semiconductors SE97, SE97B, SE98, SE98A
55
56    Datasheets:
57
58	https://www.nxp.com/documents/data_sheet/SE97.pdf
59
60	https://www.nxp.com/documents/data_sheet/SE97B.pdf
61
62	https://www.nxp.com/documents/data_sheet/SE98.pdf
63
64	https://www.nxp.com/documents/data_sheet/SE98A.pdf
65
66  * ON Semiconductor CAT34TS02, CAT6095
67
68    Datasheet:
69
70	https://www.onsemi.com/pub_link/Collateral/CAT34TS02-D.PDF
71
72	https://www.onsemi.com/pub/Collateral/CAT6095-D.PDF
73
74  * ST Microelectronics STTS424, STTS424E02, STTS2002, STTS2004, STTS3000
75
76    Datasheets:
77
78	http://www.st.com/web/en/resource/technical/document/datasheet/CD00157556.pdf
79
80	http://www.st.com/web/en/resource/technical/document/datasheet/CD00157558.pdf
81
82	http://www.st.com/web/en/resource/technical/document/datasheet/CD00266638.pdf
83
84	http://www.st.com/web/en/resource/technical/document/datasheet/CD00225278.pdf
85
86	http://www.st.com/web/en/resource/technical/document/datasheet/DM00076709.pdf
87
88  * JEDEC JC 42.4 compliant temperature sensor chips
89
90    Datasheet:
91
92	http://www.jedec.org/sites/default/files/docs/4_01_04R19.pdf
93
94
95  Common for all chips:
96
97    Prefix: 'jc42'
98
99    Addresses scanned: I2C 0x18 - 0x1f
100
101Author:
102	Guenter Roeck <linux@roeck-us.net>
103
104
105Description
106-----------
107
108This driver implements support for JEDEC JC 42.4 compliant temperature sensors,
109which are used on many DDR3 memory modules for mobile devices and servers. Some
110systems use the sensor to prevent memory overheating by automatically throttling
111the memory controller.
112
113The driver auto-detects the chips listed above, but can be manually instantiated
114to support other JC 42.4 compliant chips.
115
116Example: the following will load the driver for a generic JC 42.4 compliant
117temperature sensor at address 0x18 on I2C bus #1::
118
119	# modprobe jc42
120	# echo jc42 0x18 > /sys/bus/i2c/devices/i2c-1/new_device
121
122A JC 42.4 compliant chip supports a single temperature sensor. Minimum, maximum,
123and critical temperature can be configured. There are alarms for high, low,
124and critical thresholds.
125
126There is also an hysteresis to control the thresholds for resetting alarms.
127Per JC 42.4 specification, the hysteresis threshold can be configured to 0, 1.5,
1283.0, and 6.0 degrees C. Configured hysteresis values will be rounded to those
129limits. The chip supports only a single register to configure the hysteresis,
130which applies to all limits. This register can be written by writing into
131temp1_crit_hyst. Other hysteresis attributes are read-only.
132
133If the BIOS has configured the sensor for automatic temperature management, it
134is likely that it has locked the registers, i.e., that the temperature limits
135cannot be changed.
136
137Sysfs entries
138-------------
139
140======================= ===========================================
141temp1_input		Temperature (RO)
142temp1_min		Minimum temperature (RO or RW)
143temp1_max		Maximum temperature (RO or RW)
144temp1_crit		Critical high temperature (RO or RW)
145
146temp1_crit_hyst		Critical hysteresis temperature (RO or RW)
147temp1_max_hyst		Maximum hysteresis temperature (RO)
148
149temp1_min_alarm		Temperature low alarm
150temp1_max_alarm		Temperature high alarm
151temp1_crit_alarm	Temperature critical alarm
152======================= ===========================================
153