From cd6c8a4297ad036a155966db49982d6807e23ef8 Mon Sep 17 00:00:00 2001 From: Robert Coulson Date: Wed, 8 May 2013 22:45:53 -0700 Subject: hwmon: (ds1621) Add ds1721 chip support Update the ds1621 documentation, driver, and Kconfig with ds1721 chip support. Signed-off-by: Robert Coulson Signed-off-by: Guenter Roeck --- Documentation/hwmon/ds1621 | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621 index 5e97f333c4df..d66f76f9d85d 100644 --- a/Documentation/hwmon/ds1621 +++ b/Documentation/hwmon/ds1621 @@ -2,16 +2,22 @@ Kernel driver ds1621 ==================== Supported chips: - * Dallas Semiconductor DS1621 + * Dallas Semiconductor / Maxim Integrated DS1621 Prefix: 'ds1621' Addresses scanned: I2C 0x48 - 0x4f - Datasheet: Publicly available at the Dallas Semiconductor website - http://www.dalsemi.com/ + Datasheet: Publicly available from www.maximintegrated.com + * Dallas Semiconductor DS1625 - Prefix: 'ds1621' + Prefix: + 'ds1621' - if binding via _detect function + 'ds1625' - explicit instantiation + Addresses scanned: I2C 0x48 - 0x4f + Datasheet: Publicly available from www.datasheetarchive.com + + * Maxim Integrated DS1721 + Prefix: 'ds1721' Addresses scanned: I2C 0x48 - 0x4f - Datasheet: Publicly available at the Dallas Semiconductor website - http://www.dalsemi.com/ + Datasheet: Publicly available from www.maximintegrated.com Authors: Christian W. Zuckschwerdt @@ -61,3 +67,11 @@ with neither of the alarms set. Temperature conversion of the DS1621 takes up to 1000ms; internal access to non-volatile registers may last for 10ms or below. + +The DS1625 is pin compatible and functionally equivalent with the DS1621, +but the DS1621 is meant to replace it. + +The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0 +degree Celsius over a -10 to +85 degree range, a minimum/maximum alarm +default setting of 75 and 80 degrees respectively, and a maximum conversion +time of 750ms. -- cgit v1.2.3 From 3a8fe3315571e896489d2e271ffe7f935bfc5ce8 Mon Sep 17 00:00:00 2001 From: Robert Coulson Date: Wed, 8 May 2013 22:45:54 -0700 Subject: hwmon: (ds1621) Add ds1721 update interval sysfs attribute The ds1721 device can be configured for 9..12 bit resolutions; add a sysfs attribute for userspace to configure this attribute. The definition, description, details, and usage are shown in the documentation and were crafted from an LM73 driver patch done by Chris Verges & Guenter Roeck). Signed-off-by: Robert Coulson Signed-off-by: Guenter Roeck --- Documentation/hwmon/ds1621 | 65 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621 index d66f76f9d85d..b61e77c6b1cb 100644 --- a/Documentation/hwmon/ds1621 +++ b/Documentation/hwmon/ds1621 @@ -75,3 +75,68 @@ The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0 degree Celsius over a -10 to +85 degree range, a minimum/maximum alarm default setting of 75 and 80 degrees respectively, and a maximum conversion time of 750ms. + +In addition, the DS1721 supports four resolution settings from 9 to 12 bits +(defined in degrees C per LSB: 0.5, 0.25, 0.125, and 0.0625, respectifully), +that are set at device power on to the highest resolution: 12-bits (0.0625 degree C). + +Changing the DS1721 resolution mode affects the conversion time and can be +done from userspace, via the device 'update_interval' sysfs attribute. This +attribute will normalize range of input values to the device maximum resolution +values defined in the datasheet as such: + +Resolution Conversion Time Input Range + (C/LSB) (msec) (msec) +-------------------------------------------- +0.5 93.75 0....94 +0.25 187.5 95...187 +0.125 375 188..375 +0.0625 750 376..infinity +-------------------------------------- + +The following examples show how the 'update_interval' attribute can be +used to change the conversion time: + +$ cat update_interval +750 +$ cat temp1_input +22062 +$ +$ echo 300 > update_interval +$ cat update_interval +375 +$ cat temp1_input +22125 +$ +$ echo 150 > update_interval +$ cat update_interval +188 +$ cat temp1_input +22250 +$ +$ echo 1 > update_interval +$ cat update_interval +94 +$ cat temp1_input +22000 +$ +$ echo 1000 > update_interval +$ cat update_interval +750 +$ cat temp1_input +22062 +$ + +As shown, the ds1621 driver automatically adjusts the 'update_interval' +user input, via a step function. Reading back the 'update_interval' value +after a write operation provides the conversion time used by the device. + +Mathematically, the resolution can be derived from the conversion time +via the following function: + + g(x) = 0.5 * [minimum_conversion_time/x] + +where: + -> 'x' = the output from 'update_interval' + -> 'g(x)' = the resolution in degrees C per LSB. + -> 93.75ms = minimum conversion time -- cgit v1.2.3 From 79c1cc1c90c0ccaddd20965ea19205c54addd5f7 Mon Sep 17 00:00:00 2001 From: Robert Coulson Date: Thu, 16 May 2013 15:10:41 -0700 Subject: hwmon: (ds1621) Add ds1631 chip support to ds1621 driver and documentation Add definitions, information, and code for ds1631 chip support to the ds1621 driver. Signed-off-by: Robert Coulson Signed-off-by: Guenter Roeck --- Documentation/hwmon/ds1621 | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621 index b61e77c6b1cb..1ebaa2485770 100644 --- a/Documentation/hwmon/ds1621 +++ b/Documentation/hwmon/ds1621 @@ -14,6 +14,11 @@ Supported chips: Addresses scanned: I2C 0x48 - 0x4f Datasheet: Publicly available from www.datasheetarchive.com + * Maxim Integrated DS1631 + Prefix: 'ds1631' + Addresses scanned: I2C 0x48 - 0x4f + Datasheet: Publicly available from www.maximintegrated.com + * Maxim Integrated DS1721 Prefix: 'ds1721' Addresses scanned: I2C 0x48 - 0x4f @@ -69,7 +74,15 @@ Temperature conversion of the DS1621 takes up to 1000ms; internal access to non-volatile registers may last for 10ms or below. The DS1625 is pin compatible and functionally equivalent with the DS1621, -but the DS1621 is meant to replace it. +but the DS1621 is meant to replace it. The DS1631 and DS1721 are also +pin compatible with the DS1621, but provide multi-resolution support. + +Since there is no version register, there is no unique identification +for these devices. In addition, the DS1631 and DS1721 will emulate a +DS1621 device, if not explicitly instantiated (why? because the detect +function compares the temperature register values bits and checks for a +9-bit resolution). Therefore, for correct device identification and +functionality, explicit device instantiation is required. The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0 degree Celsius over a -10 to +85 degree range, a minimum/maximum alarm @@ -78,9 +91,17 @@ time of 750ms. In addition, the DS1721 supports four resolution settings from 9 to 12 bits (defined in degrees C per LSB: 0.5, 0.25, 0.125, and 0.0625, respectifully), -that are set at device power on to the highest resolution: 12-bits (0.0625 degree C). +that are set at device power on to the highest resolution: 12-bits. + +One additional note about the ds1721 is that although the data sheet says +the temperature flags (THF and TLF) are used internally, these flags do +get set and cleared as the actual temperature crosses the min or max settings. + +The DS1631 is also pin compatible with the DS1621 and feature compatible with +the DS1721, however the DS1631 accuracy is +/- 0.5 degree Celsius over the +same range. -Changing the DS1721 resolution mode affects the conversion time and can be +Changing the DS1631/1721 resolution mode affects the conversion time and can be done from userspace, via the device 'update_interval' sysfs attribute. This attribute will normalize range of input values to the device maximum resolution values defined in the datasheet as such: -- cgit v1.2.3 From ed7c34e89d1e9d07f787a51571be0b96ae93d678 Mon Sep 17 00:00:00 2001 From: Robert Coulson Date: Thu, 23 May 2013 09:22:22 -0700 Subject: hwmon: (ds1621) Remove detect function Due to a lack of device and vendor identification registers, the Dallas/Maxim DS16xx devices cannot be uniquely detected, sometimes resulting in false positives. Therefore, the detect function is being removed in favor of explicit device instantiation. Signed-off-by: Robert Coulson Acked-by: Jean Delvare Signed-off-by: Guenter Roeck --- Documentation/hwmon/ds1621 | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-) (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621 index 1ebaa2485770..83780660f5b1 100644 --- a/Documentation/hwmon/ds1621 +++ b/Documentation/hwmon/ds1621 @@ -4,24 +4,22 @@ Kernel driver ds1621 Supported chips: * Dallas Semiconductor / Maxim Integrated DS1621 Prefix: 'ds1621' - Addresses scanned: I2C 0x48 - 0x4f + Addresses scanned: none Datasheet: Publicly available from www.maximintegrated.com * Dallas Semiconductor DS1625 - Prefix: - 'ds1621' - if binding via _detect function - 'ds1625' - explicit instantiation - Addresses scanned: I2C 0x48 - 0x4f + Prefix: 'ds1625' + Addresses scanned: none Datasheet: Publicly available from www.datasheetarchive.com * Maxim Integrated DS1631 Prefix: 'ds1631' - Addresses scanned: I2C 0x48 - 0x4f + Addresses scanned: none Datasheet: Publicly available from www.maximintegrated.com * Maxim Integrated DS1721 Prefix: 'ds1721' - Addresses scanned: I2C 0x48 - 0x4f + Addresses scanned: none Datasheet: Publicly available from www.maximintegrated.com Authors: @@ -77,12 +75,13 @@ The DS1625 is pin compatible and functionally equivalent with the DS1621, but the DS1621 is meant to replace it. The DS1631 and DS1721 are also pin compatible with the DS1621, but provide multi-resolution support. -Since there is no version register, there is no unique identification -for these devices. In addition, the DS1631 and DS1721 will emulate a -DS1621 device, if not explicitly instantiated (why? because the detect -function compares the temperature register values bits and checks for a -9-bit resolution). Therefore, for correct device identification and -functionality, explicit device instantiation is required. +Since there is no version or vendor identification register, there is +no unique identification for these devices. Therefore, explicit device +instantiation is required for correct device identification and functionality. + +And, for correct identification and operation, each device must be +explicitly instantiated, one device per address, in this address +range: 0x48..0x4f. The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0 degree Celsius over a -10 to +85 degree range, a minimum/maximum alarm -- cgit v1.2.3 From 260f81ffc1b9f09dde355caa09e4b312756666f0 Mon Sep 17 00:00:00 2001 From: Robert Coulson Date: Mon, 10 Jun 2013 18:46:02 -0700 Subject: hwmon: (ds1621) Add DS1731 chip support to ds1621 driver These changes add DS1731 chip support to the ds1621 driver, Kconfig, and documentation. Signed-off-by: Robert Coulson Signed-off-by: Guenter Roeck --- Documentation/hwmon/ds1621 | 31 ++++++++++++++++++------------- 1 file changed, 18 insertions(+), 13 deletions(-) (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621 index 83780660f5b1..c0817f7934e4 100644 --- a/Documentation/hwmon/ds1621 +++ b/Documentation/hwmon/ds1621 @@ -22,6 +22,11 @@ Supported chips: Addresses scanned: none Datasheet: Publicly available from www.maximintegrated.com + * Maxim Integrated DS1731 + Prefix: 'ds1731' + Addresses scanned: none + Datasheet: Publicly available from www.maximintegrated.com + Authors: Christian W. Zuckschwerdt valuable contributions by Jan M. Sendler @@ -72,8 +77,8 @@ Temperature conversion of the DS1621 takes up to 1000ms; internal access to non-volatile registers may last for 10ms or below. The DS1625 is pin compatible and functionally equivalent with the DS1621, -but the DS1621 is meant to replace it. The DS1631 and DS1721 are also -pin compatible with the DS1621, but provide multi-resolution support. +but the DS1621 is meant to replace it. The DS1631, DS1721, and DS1731 are +also pin compatible with the DS1621, but provide multi-resolution support. Since there is no version or vendor identification register, there is no unique identification for these devices. Therefore, explicit device @@ -84,26 +89,26 @@ explicitly instantiated, one device per address, in this address range: 0x48..0x4f. The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0 -degree Celsius over a -10 to +85 degree range, a minimum/maximum alarm -default setting of 75 and 80 degrees respectively, and a maximum conversion -time of 750ms. +degree Celsius (from -10 to +85 degrees), a minimum/maximum alarm default +setting of 75 and 80 degrees, and a maximum conversion time of 750ms. In addition, the DS1721 supports four resolution settings from 9 to 12 bits -(defined in degrees C per LSB: 0.5, 0.25, 0.125, and 0.0625, respectifully), +(defined in degrees C per LSB: 0.5, 0.25, 0.125, and 0.0625, respectively), that are set at device power on to the highest resolution: 12-bits. One additional note about the ds1721 is that although the data sheet says the temperature flags (THF and TLF) are used internally, these flags do get set and cleared as the actual temperature crosses the min or max settings. -The DS1631 is also pin compatible with the DS1621 and feature compatible with -the DS1721, however the DS1631 accuracy is +/- 0.5 degree Celsius over the -same range. +The DS1631 and DS1731 are pin compatible with the DS1621 and feature compatible +with the DS1721. However, the DS1631 accuracy is +/- 0.5 degree Celsius (from 0 +to +70 degrees), while the DS1731 accuracy is +/-1 degree Celsius (from -10 to ++85 degrees). -Changing the DS1631/1721 resolution mode affects the conversion time and can be -done from userspace, via the device 'update_interval' sysfs attribute. This -attribute will normalize range of input values to the device maximum resolution -values defined in the datasheet as such: +The resolution mode for the DS1631, DS1721, or DS1731 can be changed from +userspace, via the device 'update_interval' sysfs attribute. This attribute +will normalize the range of input values to the device maximum resolution +values defined in the datasheet as follows: Resolution Conversion Time Input Range (C/LSB) (msec) (msec) -- cgit v1.2.3 From 87438c2c5483a7ab445c14a8855fd309ae79b4e6 Mon Sep 17 00:00:00 2001 From: Robert Coulson Date: Mon, 10 Jun 2013 18:46:03 -0700 Subject: hwmon: (ds1621) Update documentation Replace some written information with tables to improve readability and to simplify adding newer devices in the future. Signed-off-by: Robert Coulson Signed-off-by: Guenter Roeck --- Documentation/hwmon/ds1621 | 80 +++++++++++++++++++++++++++++----------------- 1 file changed, 50 insertions(+), 30 deletions(-) (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621 index c0817f7934e4..896cdc972ca8 100644 --- a/Documentation/hwmon/ds1621 +++ b/Documentation/hwmon/ds1621 @@ -73,37 +73,57 @@ any of the limits have ever been met or exceeded since last power-up or reset. Be aware: When testing, it showed that the status of Tout can change with neither of the alarms set. -Temperature conversion of the DS1621 takes up to 1000ms; internal access to -non-volatile registers may last for 10ms or below. - -The DS1625 is pin compatible and functionally equivalent with the DS1621, -but the DS1621 is meant to replace it. The DS1631, DS1721, and DS1731 are -also pin compatible with the DS1621, but provide multi-resolution support. - Since there is no version or vendor identification register, there is no unique identification for these devices. Therefore, explicit device -instantiation is required for correct device identification and functionality. - -And, for correct identification and operation, each device must be -explicitly instantiated, one device per address, in this address -range: 0x48..0x4f. +instantiation is required for correct device identification and functionality +(one device per address in this address range: 0x48..0x4f). -The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0 -degree Celsius (from -10 to +85 degrees), a minimum/maximum alarm default -setting of 75 and 80 degrees, and a maximum conversion time of 750ms. - -In addition, the DS1721 supports four resolution settings from 9 to 12 bits -(defined in degrees C per LSB: 0.5, 0.25, 0.125, and 0.0625, respectively), -that are set at device power on to the highest resolution: 12-bits. - -One additional note about the ds1721 is that although the data sheet says -the temperature flags (THF and TLF) are used internally, these flags do -get set and cleared as the actual temperature crosses the min or max settings. - -The DS1631 and DS1731 are pin compatible with the DS1621 and feature compatible -with the DS1721. However, the DS1631 accuracy is +/- 0.5 degree Celsius (from 0 -to +70 degrees), while the DS1731 accuracy is +/-1 degree Celsius (from -10 to -+85 degrees). +The DS1625 is pin compatible and functionally equivalent with the DS1621, +but the DS1621 is meant to replace it. The DS1631, DS1721, and DS1731 are +also pin compatible with the DS1621 and provide multi-resolution support. + +Additionally, the DS1721 data sheet says the temperature flags (THF and TLF) +are used internally, however, these flags do get set and cleared as the actual +temperature crosses the min or max settings (which by default are set to 75 +and 80 degrees respectively). + +Temperature Conversion: +----------------------- +DS1621 - 750ms (older devices may take up to 1000ms) +DS1625 - 500ms +DS1631 - 93ms..750ms for 9..12 bits resolution, respectively. +DS1721 - 93ms..750ms for 9..12 bits resolution, respectively. +DS1731 - 93ms..750ms for 9..12 bits resolution, respectively. + +Note: +On the DS1621, internal access to non-volatile registers may last for 10ms +or less (unverified on the other devices). + +Temperature Accuracy: +--------------------- +DS1621: +/- 0.5 degree Celsius (from 0 to +70 degrees) +DS1625: +/- 0.5 degree Celsius (from 0 to +70 degrees) +DS1631: +/- 0.5 degree Celsius (from 0 to +70 degrees) +DS1721: +/- 1.0 degree Celsius (from -10 to +85 degrees) +DS1731: +/- 1.0 degree Celsius (from -10 to +85 degrees) + +Note: +Please refer to the device datasheets for accuracy at other temperatures. + +Temperature Resolution: +----------------------- +As mentioned above, the DS1631, DS1721, and DS1731 provide multi-resolution +support, which is achieved via the R0 and R1 config register bits, where: + +R0..R1 +------ + 0 0 => 9 bits, 0.5 degrees Celcius + 1 0 => 10 bits, 0.25 degrees Celcius + 0 1 => 11 bits, 0.125 degrees Celcius + 1 1 => 12 bits, 0.0625 degrees Celcius + +Note: +At initial device power-on, the default resolution is set to 12-bits. The resolution mode for the DS1631, DS1721, or DS1731 can be changed from userspace, via the device 'update_interval' sysfs attribute. This attribute @@ -112,12 +132,12 @@ values defined in the datasheet as follows: Resolution Conversion Time Input Range (C/LSB) (msec) (msec) --------------------------------------------- +------------------------------------------------ 0.5 93.75 0....94 0.25 187.5 95...187 0.125 375 188..375 0.0625 750 376..infinity --------------------------------------- +------------------------------------------------ The following examples show how the 'update_interval' attribute can be used to change the conversion time: -- cgit v1.2.3 From 31e7ad74f6044ffec112fd4975c07b797589d89c Mon Sep 17 00:00:00 2001 From: Tang Yuantian Date: Wed, 19 Jun 2013 14:50:20 +0800 Subject: hwmon: (ina2xx) Add device tree support to pass the shunt resistor Adding another way that is device tree to pass the shunt resistor value to driver except for platform data. Signed-off-by: Tang Yuantian [Guenter Roeck: Added missing of.h include] Signed-off-by: Guenter Roeck --- Documentation/hwmon/ina2xx | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/ina2xx b/Documentation/hwmon/ina2xx index 03444f9d833f..4223c2d3b508 100644 --- a/Documentation/hwmon/ina2xx +++ b/Documentation/hwmon/ina2xx @@ -44,4 +44,6 @@ The INA226 monitors both a shunt voltage drop and bus supply voltage. The INA230 is a high or low side current shunt and power monitor with an I2C interface. The INA230 monitors both a shunt voltage drop and bus supply voltage. -The shunt value in micro-ohms can be set via platform data. +The shunt value in micro-ohms can be set via platform data or device tree. +Please refer to the Documentation/devicetree/bindings/i2c/ina2xx.txt for bindings +if the device tree is used. -- cgit v1.2.3 From 594fbe713bf60073ed884dc317a74dd5b327aba7 Mon Sep 17 00:00:00 2001 From: Arnaud Ebalard Date: Thu, 20 Jun 2013 22:21:04 +0200 Subject: Add support for GMT G762/G763 PWM fan controllers GMT G762/763 fan speed PWM controller is connected directly to a fan and performs closed-loop or open-loop control of the fan speed. Two modes - PWM or DC - are supported by the chip. Introduced driver provides various knobs to control the operations of the chip (via sysfs interface). Specific characteristics of the system can be passed either using board init code or via DT. Documentation for both the driver and DT bindings are also provided. Signed-off-by: Arnaud Ebalard Tested-by: Simon Guinot Signed-off-by: Guenter Roeck --- Documentation/hwmon/g762 | 65 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 Documentation/hwmon/g762 (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/g762 b/Documentation/hwmon/g762 new file mode 100644 index 000000000000..923db9c5b5bc --- /dev/null +++ b/Documentation/hwmon/g762 @@ -0,0 +1,65 @@ +Kernel driver g762 +================== + +The GMT G762 Fan Speed PWM Controller is connected directly to a fan +and performs closed-loop or open-loop control of the fan speed. Two +modes - PWM or DC - are supported by the device. + +For additional information, a detailed datasheet is available at +http://natisbad.org/NAS/ref/GMT_EDS-762_763-080710-0.2.pdf. sysfs +bindings are described in Documentation/hwmon/sysfs-interface. + +The following entries are available to the user in a subdirectory of +/sys/bus/i2c/drivers/g762/ to control the operation of the device. +This can be done manually using the following entries but is usually +done via a userland daemon like fancontrol. + +Note that those entries do not provide ways to setup the specific +hardware characteristics of the system (reference clock, pulses per +fan revolution, ...); Those can be modified via devicetree bindings +documented in Documentation/devicetree/bindings/hwmon/g762.txt or +using a specific platform_data structure in board initialization +file (see include/linux/platform_data/g762.h). + + fan1_target: set desired fan speed. This only makes sense in closed-loop + fan speed control (i.e. when pwm1_enable is set to 2). + + fan1_input: provide current fan rotation value in RPM as reported by + the fan to the device. + + fan1_div: fan clock divisor. Supported value are 1, 2, 4 and 8. + + fan1_pulses: number of pulses per fan revolution. Supported values + are 2 and 4. + + fan1_fault: reports fan failure, i.e. no transition on fan gear pin for + about 0.7s (if the fan is not voluntarily set off). + + fan1_alarm: in closed-loop control mode, if fan RPM value is 25% out + of the programmed value for over 6 seconds 'fan1_alarm' is + set to 1. + + pwm1_enable: set current fan speed control mode i.e. 1 for manual fan + speed control (open-loop) via pwm1 described below, 2 for + automatic fan speed control (closed-loop) via fan1_target + above. + + pwm1_mode: set or get fan driving mode: 1 for PWM mode, 0 for DC mode. + + pwm1: get or set PWM fan control value in open-loop mode. This is an + integer value between 0 and 255. 0 stops the fan, 255 makes + it run at full speed. + +Both in PWM mode ('pwm1_mode' set to 1) and DC mode ('pwm1_mode' set to 0), +when current fan speed control mode is open-loop ('pwm1_enable' set to 1), +the fan speed is programmed by setting a value between 0 and 255 via 'pwm1' +entry (0 stops the fan, 255 makes it run at full speed). In closed-loop mode +('pwm1_enable' set to 2), the expected rotation speed in RPM can be passed to +the chip via 'fan1_target'. In closed-loop mode, the target speed is compared +with current speed (available via 'fan1_input') by the device and a feedback +is performed to match that target value. The fan speed value is computed +based on the parameters associated with the physical characteristics of the +system: a reference clock source frequency, a number of pulses per fan +revolution, etc. + +Note that the driver will update its values at most once per second. -- cgit v1.2.3