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Add driver for Microchip MCP998X/33 and MCP998XD/33D Multichannel Automotive Temperature Monitor Family. Signed-off-by: Victor Duicu <victor.duicu@microchip.com> Link: https://lore.kernel.org/r/20260403-add-mcp9982-hwmon-v12-2-b3bfb26ff136@microchip.com [groeck: Add missing break; to avoid build warning] Signed-off-by: Guenter Roeck <linux@roeck-us.net>
112 lines
3.8 KiB
ReStructuredText
112 lines
3.8 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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Kernel driver MCP998X
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=====================
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Supported chips:
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* Microchip Technology MCP998X/MCP9933 and MCP998XD/MCP9933D
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Prefix: 'mcp9982'
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Datasheet:
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https://ww1.microchip.com/downloads/aemDocuments/documents/MSLD/ProductDocuments/DataSheets/MCP998X-Family-Data-Sheet-DS20006827.pdf
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Authors:
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- Victor Duicu <victor.duicu@microchip.com>
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Description
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-----------
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This driver implements support for the MCP998X family containing: MCP9982,
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MCP9982D, MCP9983, MCP9983D, MCP9984, MCP9984D, MCP9985, MCP9985D,
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MCP9933 and MCP9933D.
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The MCP998X Family is a high accuracy 2-wire multichannel automotive
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temperature monitor.
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The chips in the family have different numbers of external channels,
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ranging from 1 (MCP9982) to 4 channels (MCP9985). Reading diodes in
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anti-parallel connection is supported by MCP9984/85/33 and
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MCP9984D/85D/33D. Dedicated hardware shutdown circuitry is present
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only in MCP998XD and MCP9933D.
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Temperatures are read in millidegrees Celsius, ranging from -64 to
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191.875 with 0.125 precision.
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Each channel has a minimum, maximum, and critical limit alongside associated alarms.
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The chips also implement a hysteresis mechanism which applies only to the maximum
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and critical limits. The relative difference between a limit and its hysteresis
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is the same for both and the value is kept in a single register.
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The chips measure temperatures with a variable conversion rate.
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Update_interval = Conversion/Second, so the available options are:
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- 16000 (ms) = 1 conv/16 sec
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- 8000 (ms) = 1 conv/8 sec
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- 4000 (ms) = 1 conv/4 sec
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- 2000 (ms) = 1 conv/2 sec
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- 1000 (ms) = 1 conv/sec
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- 500 (ms) = 2 conv/sec
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- 250 (ms) = 4 conv/sec
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- 125 (ms) = 8 conv/sec
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- 64 (ms) = 16 conv/sec
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- 32 (ms) = 32 conv/sec
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- 16 (ms) = 64 conv/sec
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Usage Notes
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-----------
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Parameters that can be configured in devicetree:
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- anti-parallel diode mode operation
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- resistance error correction on channels 1 and 2
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- resistance error correction on channels 3 and 4
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- power state
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Chips 82/83 and 82D/83D do not support anti-parallel diode mode.
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For chips with "D" in the name resistance error correction must be on.
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Please see Documentation/devicetree/bindings/hwmon/microchip,mcp9982.yaml
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for details.
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There are two power states:
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- Active state: in which the chip is converting on all channels at the
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programmed rate.
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- Standby state: in which the host must initiate a conversion cycle.
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Chips with "D" in the name work in Active state only and those without
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can work in either state.
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Chips with "D" in the name can't set update interval slower than 1 second.
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Among the hysteresis attributes, only the tempX_crit_hyst ones are writeable
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while the others are read only. Setting tempX_crit_hyst writes the difference
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between tempX_crit and tempX_crit_hyst in the hysteresis register. The new value
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applies automatically to the other limits. At power up the device starts with
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a 10 degree hysteresis.
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Sysfs entries
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-------------
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The following attributes are supported. The temperature limits and
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update_interval are read-write. The attribute tempX_crit_hyst is read-write,
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while tempX_max_hyst is read only. All other attributes are read only.
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======================= ==================================================
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temp[1-5]_label User name for channel.
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temp[1-5]_input Measured temperature for channel.
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temp[1-5]_crit Critical temperature limit.
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temp[1-5]_crit_alarm Critical temperature limit alarm.
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temp[1-5]_crit_hyst Critical temperature limit hysteresis.
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temp[1-5]_max High temperature limit.
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temp[1-5]_max_alarm High temperature limit alarm.
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temp[1-5]_max_hyst High temperature limit hysteresis.
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temp[1-5]_min Low temperature limit.
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temp[1-5]_min_alarm Low temperature limit alarm.
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update_interval The interval at which the chip will update readings.
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======================= ==================================================
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