69 lines
3.6 KiB
Plaintext
69 lines
3.6 KiB
Plaintext
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Tegra External Temperature Sensor driver
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----------------------------------------
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This file documents the DT bindings of the NCT1008 external temperature sensor
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driver. NCT1008 belongs to a class of sensors that reports two temperatures,
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one local and one external. On Tegra systems the local sensor measures the
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board temperature and the external sensor measures the junction temperature on
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the die. The sensor is connected as an I2C slave and can be communicated with
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using the SMBus protocol. The Tegra NCT1008 driver supports TMP451 and MAX6649
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in addition to the NCT1008 sensor.
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NCT1008 driver is an I2C client that registers itself as two sensors to
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the thermal framework and supports programmable temperature alerts and
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overtemperature shutdown limits. The sensor ids are defined in
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<dt-bindings/misc/nvidia,nct1008.h>.
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Required properties :
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- compatible : The compatibility string must match the sensor that is
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being used and should be one of the following:
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- onsemi,nct72
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- ti,tmp451
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- maxim,max6649
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- reg : An I2C client property which specifies the slave address of the sensor
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on the I2C bus.
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- #thermal-sensor-cells : Should be 1. See ./thermal.txt for a description of
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this property.
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- conv-rate : Specifies the value to be programmed into the conversion rate
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register of the sensor. Valid range is 0 - 9. See the sensor datasheet for the
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exact conversion rates.
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Optional properties :
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- interrupts : An I2C client property which specifies the interrupt used by the
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sensor for temperature alerts.
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- temp-alert-gpio : This property specifies the gpio used by the sensor to
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trigger the temperature alert.
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- loc-shutdown-limit : When present, this property specifies the temperature at
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which the local sensor will assert the thermal trigger signal to the
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Power Management IC. which can be configured to reset or shutdown the device.
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In the absence of this property the over temperature shutdown from local
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sensor will be disabled. Can take any value in the valid temperature range of
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the sensor.
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- ext-shutdown-limit : Similar to the loc-shutdown-limit. Used to specify the
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over temperature shutdown limit for the external sensor.
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- extended-range : This property is used to control the range of temperature
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measurement in the sensor. Allowed values are 0,1. A value of 1 enables
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extended temperature monitoring range and a missing property disables it.
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- offset : Specifies the offset to be programmed to the offset register. The
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property is in units of 0.25C and has a valid range of -128C to 127C.
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- offset-hi-res : Similar to the offset property but allows offset to be
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programmed in units of 0.0625C.
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- support-fuse-offset : When present the driver reads the fuse registers which
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has the measured offset at a known temperature. After performing linear
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correction on the true physical temperature (which is offset + known
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temperature) a value for offset and nfactor are calculated. These values are
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then used to program the corresponding registers in the sensor hardware. The
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property takes no value.
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- alpha : Specifies the slope of the linear correction that is performed when
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support-fuse-offset is specified.
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- beta : Specifies the intercept of the linear correction that is performed when
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support-fuse-offset is specified.
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Note:
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The external temperature reported by the sensor can often be inaccurate which
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can be corrected by progamming the offset register. The NCT1008 driver allows
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offset to be specified in couple of ways as using the various offset properties
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described above. The support-fuse-offset property takes effect only if both
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offset and offset-hi-res are absent. The offset-hi-res property takes effect
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only if offset property is absent.
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