About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / hwmon / lm85




Custom Search

Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

1	Kernel driver lm85
2	==================
3	
4	Supported chips:
5	  * National Semiconductor LM85 (B and C versions)
6	    Prefix: 'lm85'
7	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
8	    Datasheet: http://www.national.com/pf/LM/LM85.html
9	  * Analog Devices ADM1027
10	    Prefix: 'adm1027'
11	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
12	    Datasheet: http://www.onsemi.com/PowerSolutions/product.do?id=ADM1027
13	  * Analog Devices ADT7463
14	    Prefix: 'adt7463'
15	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
16	    Datasheet: http://www.onsemi.com/PowerSolutions/product.do?id=ADT7463
17	  * Analog Devices ADT7468
18	    Prefix: 'adt7468'
19	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
20	    Datasheet: http://www.onsemi.com/PowerSolutions/product.do?id=ADT7468
21	  * SMSC EMC6D100, SMSC EMC6D101
22	    Prefix: 'emc6d100'
23	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
24	    Datasheet: http://www.smsc.com/media/Downloads_Public/discontinued/6d100.pdf 
25	  * SMSC EMC6D102
26	    Prefix: 'emc6d102'
27	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
28	    Datasheet: http://www.smsc.com/main/catalog/emc6d102.html
29	  * SMSC EMC6D103
30	    Prefix: 'emc6d103'
31	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
32	    Datasheet: http://www.smsc.com/main/catalog/emc6d103.html
33	  * SMSC EMC6D103S
34	    Prefix: 'emc6d103s'
35	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
36	    Datasheet: http://www.smsc.com/main/catalog/emc6d103s.html
37	
38	Authors:
39	        Philip Pokorny <ppokorny@penguincomputing.com>,
40	        Frodo Looijaard <frodol@dds.nl>,
41	        Richard Barrington <rich_b_nz@clear.net.nz>,
42	        Margit Schubert-While <margitsw@t-online.de>,
43	        Justin Thiessen <jthiessen@penguincomputing.com>
44	
45	Description
46	-----------
47	
48	This driver implements support for the National Semiconductor LM85 and
49	compatible chips including the Analog Devices ADM1027, ADT7463, ADT7468 and
50	SMSC EMC6D10x chips family.
51	
52	The LM85 uses the 2-wire interface compatible with the SMBUS 2.0
53	specification. Using an analog to digital converter it measures three (3)
54	temperatures and five (5) voltages. It has four (4) 16-bit counters for
55	measuring fan speed. Five (5) digital inputs are provided for sampling the
56	VID signals from the processor to the VRM. Lastly, there are three (3) PWM
57	outputs that can be used to control fan speed.
58	
59	The voltage inputs have internal scaling resistors so that the following
60	voltage can be measured without external resistors:
61	
62	  2.5V, 3.3V, 5V, 12V, and CPU core voltage (2.25V)
63	
64	The temperatures measured are one internal diode, and two remote diodes.
65	Remote 1 is generally the CPU temperature. These inputs are designed to
66	measure a thermal diode like the one in a Pentium 4 processor in a socket
67	423 or socket 478 package. They can also measure temperature using a
68	transistor like the 2N3904.
69	
70	A sophisticated control system for the PWM outputs is designed into the
71	LM85 that allows fan speed to be adjusted automatically based on any of the
72	three temperature sensors. Each PWM output is individually adjustable and
73	programmable. Once configured, the LM85 will adjust the PWM outputs in
74	response to the measured temperatures without further host intervention.
75	This feature can also be disabled for manual control of the PWM's.
76	
77	Each of the measured inputs (voltage, temperature, fan speed) has
78	corresponding high/low limit values. The LM85 will signal an ALARM if any
79	measured value exceeds either limit.
80	
81	The LM85 samples all inputs continuously. The lm85 driver will not read
82	the registers more often than once a second. Further, configuration data is
83	only read once each 5 minutes. There is twice as much config data as
84	measurements, so this would seem to be a worthwhile optimization.
85	
86	Special Features
87	----------------
88	
89	The LM85 has four fan speed monitoring modes. The ADM1027 has only two.
90	Both have special circuitry to compensate for PWM interactions with the
91	TACH signal from the fans. The ADM1027 can be configured to measure the
92	speed of a two wire fan, but the input conditioning circuitry is different
93	for 3-wire and 2-wire mode. For this reason, the 2-wire fan modes are not
94	exposed to user control. The BIOS should initialize them to the correct
95	mode. If you've designed your own ADM1027, you'll have to modify the
96	init_client function and add an insmod parameter to set this up.
97	
98	To smooth the response of fans to changes in temperature, the LM85 has an
99	optional filter for smoothing temperatures. The ADM1027 has the same
100	config option but uses it to rate limit the changes to fan speed instead.
101	
102	The ADM1027, ADT7463 and ADT7468 have a 10-bit ADC and can therefore
103	measure temperatures with 0.25 degC resolution. They also provide an offset
104	to the temperature readings that is automatically applied during
105	measurement. This offset can be used to zero out any errors due to traces
106	and placement. The documentation says that the offset is in 0.25 degC
107	steps, but in initial testing of the ADM1027 it was 1.00 degC steps. Analog
108	Devices has confirmed this "bug". The ADT7463 is reported to work as
109	described in the documentation. The current lm85 driver does not show the
110	offset register.
111	
112	The ADT7468 has a high-frequency PWM mode, where all PWM outputs are
113	driven by a 22.5 kHz clock. This is a global mode, not per-PWM output,
114	which means that setting any PWM frequency above 11.3 kHz will switch
115	all 3 PWM outputs to a 22.5 kHz frequency. Conversely, setting any PWM
116	frequency below 11.3 kHz will switch all 3 PWM outputs to a frequency
117	between 10 and 100 Hz, which can then be tuned separately.
118	
119	See the vendor datasheets for more information. There is application note
120	from National (AN-1260) with some additional information about the LM85.
121	The Analog Devices datasheet is very detailed and describes a procedure for
122	determining an optimal configuration for the automatic PWM control.
123	
124	The SMSC EMC6D100 & EMC6D101 monitor external voltages, temperatures, and
125	fan speeds. They use this monitoring capability to alert the system to out
126	of limit conditions and can automatically control the speeds of multiple
127	fans in a PC or embedded system. The EMC6D101, available in a 24-pin SSOP
128	package, and the EMC6D100, available in a 28-pin SSOP package, are designed
129	to be register compatible. The EMC6D100 offers all the features of the
130	EMC6D101 plus additional voltage monitoring and system control features.
131	Unfortunately it is not possible to distinguish between the package
132	versions on register level so these additional voltage inputs may read
133	zero. EMC6D102 and EMC6D103 feature additional ADC bits thus extending precision
134	of voltage and temperature channels.
135	
136	SMSC EMC6D103S is similar to EMC6D103, but does not support pwm#_auto_pwm_minctl
137	and temp#_auto_temp_off.
138	
139	Hardware Configurations
140	-----------------------
141	
142	The LM85 can be jumpered for 3 different SMBus addresses. There are
143	no other hardware configuration options for the LM85.
144	
145	The lm85 driver detects both LM85B and LM85C revisions of the chip. See the
146	datasheet for a complete description of the differences. Other than
147	identifying the chip, the driver behaves no differently with regard to
148	these two chips. The LM85B is recommended for new designs.
149	
150	The ADM1027, ADT7463 and ADT7468 chips have an optional SMBALERT output
151	that can be used to signal the chipset in case a limit is exceeded or the
152	temperature sensors fail. Individual sensor interrupts can be masked so
153	they won't trigger SMBALERT. The SMBALERT output if configured replaces one
154	of the other functions (PWM2 or IN0). This functionality is not implemented
155	in current driver.
156	
157	The ADT7463 and ADT7468 also have an optional THERM output/input which can
158	be connected to the processor PROC_HOT output. If available, the autofan
159	control dynamic Tmin feature can be enabled to keep the system temperature
160	within spec (just?!) with the least possible fan noise.
161	
162	Configuration Notes
163	-------------------
164	
165	Besides standard interfaces driver adds following:
166	
167	* Temperatures and Zones
168	
169	Each temperature sensor is associated with a Zone. There are three
170	sensors and therefore three zones (# 1, 2 and 3). Each zone has the following
171	temperature configuration points:
172	
173	* temp#_auto_temp_off - temperature below which fans should be off or spinning very low.
174	* temp#_auto_temp_min - temperature over which fans start to spin.
175	* temp#_auto_temp_max - temperature when fans spin at full speed.
176	* temp#_auto_temp_crit - temperature when all fans will run full speed.
177	
178	* PWM Control
179	
180	There are three PWM outputs. The LM85 datasheet suggests that the
181	pwm3 output control both fan3 and fan4. Each PWM can be individually
182	configured and assigned to a zone for its control value. Each PWM can be
183	configured individually according to the following options.
184	
185	* pwm#_auto_pwm_min - this specifies the PWM value for temp#_auto_temp_off
186	                      temperature. (PWM value from 0 to 255)
187	
188	* pwm#_auto_pwm_minctl - this flags selects for temp#_auto_temp_off temperature
189	                         the behaviour of fans. Write 1 to let fans spinning at
190				 pwm#_auto_pwm_min or write 0 to let them off.
191	
192	NOTE: It has been reported that there is a bug in the LM85 that causes the flag
193	to be associated with the zones not the PWMs. This contradicts all the
194	published documentation. Setting pwm#_min_ctl in this case actually affects all
195	PWMs controlled by zone '#'.
196	
197	* PWM Controlling Zone selection
198	
199	* pwm#_auto_channels - controls zone that is associated with PWM
200	
201	Configuration choices:
202	
203	   Value     Meaning
204	  ------  ------------------------------------------------
205	      1    Controlled by Zone 1
206	      2    Controlled by Zone 2
207	      3    Controlled by Zone 3
208	     23    Controlled by higher temp of Zone 2 or 3
209	    123    Controlled by highest temp of Zone 1, 2 or 3
210	      0    PWM always 0%  (off)
211	     -1    PWM always 100%  (full on)
212	     -2    Manual control (write to 'pwm#' to set)
213	
214	The National LM85's have two vendor specific configuration
215	features. Tach. mode and Spinup Control. For more details on these,
216	see the LM85 datasheet or Application Note AN-1260. These features
217	are not currently supported by the lm85 driver.
218	
219	The Analog Devices ADM1027 has several vendor specific enhancements.
220	The number of pulses-per-rev of the fans can be set, Tach monitoring
221	can be optimized for PWM operation, and an offset can be applied to
222	the temperatures to compensate for systemic errors in the
223	measurements. These features are not currently supported by the lm85
224	driver.
225	
226	In addition to the ADM1027 features, the ADT7463 and ADT7468 also have
227	Tmin control and THERM asserted counts. Automatic Tmin control acts to
228	adjust the Tmin value to maintain the measured temperature sensor at a
229	specified temperature. There isn't much documentation on this feature in
230	the ADT7463 data sheet. This is not supported by current driver.
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.