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-Kernel driver pc87360
-=====================
-
-Supported chips:
- * National Semiconductor PC87360, PC87363, PC87364, PC87365 and PC87366
- Prefixes: 'pc87360', 'pc87363', 'pc87364', 'pc87365', 'pc87366'
- Addresses scanned: none, address read from Super I/O config space
- Datasheets: No longer available
-
-Authors: Jean Delvare <khali@linux-fr.org>
-
-Thanks to Sandeep Mehta, Tonko de Rooy and Daniel Ceregatti for testing.
-Thanks to Rudolf Marek for helping me investigate conversion issues.
-
-
-Module Parameters
------------------
-
-* init int
- Chip initialization level:
- 0: None
- *1: Forcibly enable internal voltage and temperature channels, except in9
- 2: Forcibly enable all voltage and temperature channels, except in9
- 3: Forcibly enable all voltage and temperature channels, including in9
-
-Note that this parameter has no effect for the PC87360, PC87363 and PC87364
-chips.
-
-Also note that for the PC87366, initialization levels 2 and 3 don't enable
-all temperature channels, because some of them share pins with each other,
-so they can't be used at the same time.
-
-
-Description
------------
-
-The National Semiconductor PC87360 Super I/O chip contains monitoring and
-PWM control circuitry for two fans. The PC87363 chip is similar, and the
-PC87364 chip has monitoring and PWM control for a third fan.
-
-The National Semiconductor PC87365 and PC87366 Super I/O chips are complete
-hardware monitoring chipsets, not only controlling and monitoring three fans,
-but also monitoring eleven voltage inputs and two (PC87365) or up to four
-(PC87366) temperatures.
-
- Chip #vin #fan #pwm #temp devid
-
- PC87360 - 2 2 - 0xE1
- PC87363 - 2 2 - 0xE8
- PC87364 - 3 3 - 0xE4
- PC87365 11 3 3 2 0xE5
- PC87366 11 3 3 3-4 0xE9
-
-The driver assumes that no more than one chip is present, and one of the
-standard Super I/O addresses is used (0x2E/0x2F or 0x4E/0x4F)
-
-Fan Monitoring
---------------
-
-Fan rotation speeds are reported in RPM (revolutions per minute). An alarm
-is triggered if the rotation speed has dropped below a programmable limit.
-A different alarm is triggered if the fan speed is too low to be measured.
-
-Fan readings are affected by a programmable clock divider, giving the
-readings more range or accuracy. Usually, users have to learn how it works,
-but this driver implements dynamic clock divider selection, so you don't
-have to care no more.
-
-For reference, here are a few values about clock dividers:
-
- slowest accuracy highest
- measurable around 3000 accurate
- divider speed (RPM) RPM (RPM) speed (RPM)
- 1 1882 18 6928
- 2 941 37 4898
- 4 470 74 3464
- 8 235 150 2449
-
-For the curious, here is how the values above were computed:
- * slowest measurable speed: clock/(255*divider)
- * accuracy around 3000 RPM: 3000^2/clock
- * highest accurate speed: sqrt(clock*100)
-The clock speed for the PC87360 family is 480 kHz. I arbitrarily chose 100
-RPM as the lowest acceptable accuracy.
-
-As mentioned above, you don't have to care about this no more.
-
-Note that not all RPM values can be represented, even when the best clock
-divider is selected. This is not only true for the measured speeds, but
-also for the programmable low limits, so don't be surprised if you try to
-set, say, fan1_min to 2900 and it finally reads 2909.
-
-
-Fan Control
------------
-
-PWM (pulse width modulation) values range from 0 to 255, with 0 meaning
-that the fan is stopped, and 255 meaning that the fan goes at full speed.
-
-Be extremely careful when changing PWM values. Low PWM values, even
-non-zero, can stop the fan, which may cause irreversible damage to your
-hardware if temperature increases too much. When changing PWM values, go
-step by step and keep an eye on temperatures.
-
-One user reported problems with PWM. Changing PWM values would break fan
-speed readings. No explanation nor fix could be found.
-
-
-Temperature Monitoring
-----------------------
-
-Temperatures are reported in degrees Celsius. Each temperature measured has
-associated low, high and overtemperature limits, each of which triggers an
-alarm when crossed.
-
-The first two temperature channels are external. The third one (PC87366
-only) is internal.
-
-The PC87366 has three additional temperature channels, based on
-thermistors (as opposed to thermal diodes for the first three temperature
-channels). For technical reasons, these channels are held by the VLM
-(voltage level monitor) logical device, not the TMS (temperature
-measurement) one. As a consequence, these temperatures are exported as
-voltages, and converted into temperatures in user-space.
-
-Note that these three additional channels share their pins with the
-external thermal diode channels, so you (physically) can't use them all at
-the same time. Although it should be possible to mix the two sensor types,
-the documents from National Semiconductor suggest that motherboard
-manufacturers should choose one type and stick to it. So you will more
-likely have either channels 1 to 3 (thermal diodes) or 3 to 6 (internal
-thermal diode, and thermistors).
-
-
-Voltage Monitoring
-------------------
-
-Voltages are reported relatively to a reference voltage, either internal or
-external. Some of them (in7:Vsb, in8:Vdd and in10:AVdd) are divided by two
-internally, you will have to compensate in sensors.conf. Others (in0 to in6)
-are likely to be divided externally. The meaning of each of these inputs as
-well as the values of the resistors used for division is left to the
-motherboard manufacturers, so you will have to document yourself and edit
-sensors.conf accordingly. National Semiconductor has a document with
-recommended resistor values for some voltages, but this still leaves much
-room for per motherboard specificities, unfortunately. Even worse,
-motherboard manufacturers don't seem to care about National Semiconductor's
-recommendations.
-
-Each voltage measured has associated low and high limits, each of which
-triggers an alarm when crossed.
-
-When available, VID inputs are used to provide the nominal CPU Core voltage.
-The driver will default to VRM 9.0, but this can be changed from user-space.
-The chipsets can handle two sets of VID inputs (on dual-CPU systems), but
-the driver will only export one for now. This may change later if there is
-a need.
-
-
-General Remarks
----------------
-
-If an alarm triggers, it will remain triggered until the hardware register
-is read at least once. This means that the cause for the alarm may already
-have disappeared! Note that all hardware registers are read whenever any
-data is read (unless it is less than 2 seconds since the last update, in
-which case cached values are returned instead). As a consequence, when
-a once-only alarm triggers, it may take 2 seconds for it to show, and 2
-more seconds for it to disappear.
-
-Monitoring of in9 isn't enabled at lower init levels (<3) because that
-channel measures the battery voltage (Vbat). It is a known fact that
-repeatedly sampling the battery voltage reduces its lifetime. National
-Semiconductor smartly designed their chipset so that in9 is sampled only
-once every 1024 sampling cycles (that is every 34 minutes at the default
-sampling rate), so the effect is attenuated, but still present.
-
-
-Limitations
------------
-
-The datasheets suggests that some values (fan mins, fan dividers)
-shouldn't be changed once the monitoring has started, but we ignore that
-recommendation. We'll reconsider if it actually causes trouble.