196 lines
6.0 KiB
C
196 lines
6.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* nct6775-i2c - I2C driver for the hardware monitoring functionality of
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* Nuvoton NCT677x Super-I/O chips
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*
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* Copyright (C) 2022 Zev Weiss <zev@bewilderbeest.net>
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*
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* This driver interacts with the chip via it's "back door" i2c interface, as
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* is often exposed to a BMC. Because the host may still be operating the
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* chip via the ("front door") LPC interface, this driver cannot assume that
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* it actually has full control of the chip, and in particular must avoid
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* making any changes that could confuse the host's LPC usage of it. It thus
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* operates in a strictly read-only fashion, with the only exception being the
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* bank-select register (which seems, thankfully, to be replicated for the i2c
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* interface so it doesn't affect the LPC interface).
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/i2c.h>
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#include <linux/hwmon.h>
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#include <linux/hwmon-sysfs.h>
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#include <linux/err.h>
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#include <linux/of_device.h>
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#include <linux/regmap.h>
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#include "nct6775.h"
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static int nct6775_i2c_read(void *ctx, unsigned int reg, unsigned int *val)
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{
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int ret;
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u32 tmp;
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u8 bank = reg >> 8;
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struct nct6775_data *data = ctx;
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struct i2c_client *client = data->driver_data;
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if (bank != data->bank) {
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ret = i2c_smbus_write_byte_data(client, NCT6775_REG_BANK, bank);
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if (ret)
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return ret;
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data->bank = bank;
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}
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ret = i2c_smbus_read_byte_data(client, reg & 0xff);
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if (ret < 0)
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return ret;
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tmp = ret;
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if (nct6775_reg_is_word_sized(data, reg)) {
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ret = i2c_smbus_read_byte_data(client, (reg & 0xff) + 1);
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if (ret < 0)
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return ret;
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tmp = (tmp << 8) | ret;
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}
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*val = tmp;
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return 0;
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}
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/*
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* The write operation is a dummy so as not to disturb anything being done
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* with the chip via LPC.
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*/
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static int nct6775_i2c_write(void *ctx, unsigned int reg, unsigned int value)
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{
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struct nct6775_data *data = ctx;
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struct i2c_client *client = data->driver_data;
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dev_dbg(&client->dev, "skipping attempted write: %02x -> %03x\n", value, reg);
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/*
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* This is a lie, but writing anything but the bank-select register is
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* something this driver shouldn't be doing.
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*/
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return 0;
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}
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static const struct of_device_id __maybe_unused nct6775_i2c_of_match[] = {
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{ .compatible = "nuvoton,nct6106", .data = (void *)nct6106, },
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{ .compatible = "nuvoton,nct6116", .data = (void *)nct6116, },
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{ .compatible = "nuvoton,nct6775", .data = (void *)nct6775, },
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{ .compatible = "nuvoton,nct6776", .data = (void *)nct6776, },
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{ .compatible = "nuvoton,nct6779", .data = (void *)nct6779, },
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{ .compatible = "nuvoton,nct6791", .data = (void *)nct6791, },
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{ .compatible = "nuvoton,nct6792", .data = (void *)nct6792, },
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{ .compatible = "nuvoton,nct6793", .data = (void *)nct6793, },
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{ .compatible = "nuvoton,nct6795", .data = (void *)nct6795, },
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{ .compatible = "nuvoton,nct6796", .data = (void *)nct6796, },
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{ .compatible = "nuvoton,nct6797", .data = (void *)nct6797, },
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{ .compatible = "nuvoton,nct6798", .data = (void *)nct6798, },
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{ },
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};
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MODULE_DEVICE_TABLE(of, nct6775_i2c_of_match);
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static const struct i2c_device_id nct6775_i2c_id[] = {
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{ "nct6106", nct6106 },
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{ "nct6116", nct6116 },
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{ "nct6775", nct6775 },
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{ "nct6776", nct6776 },
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{ "nct6779", nct6779 },
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{ "nct6791", nct6791 },
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{ "nct6792", nct6792 },
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{ "nct6793", nct6793 },
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{ "nct6795", nct6795 },
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{ "nct6796", nct6796 },
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{ "nct6797", nct6797 },
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{ "nct6798", nct6798 },
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{ }
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};
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MODULE_DEVICE_TABLE(i2c, nct6775_i2c_id);
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static int nct6775_i2c_probe_init(struct nct6775_data *data)
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{
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u32 tsi_channel_mask;
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struct i2c_client *client = data->driver_data;
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/*
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* The i2c interface doesn't provide access to the control registers
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* needed to determine the presence of other fans, but fans 1 and 2
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* are (in principle) always there.
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*
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* In practice this is perhaps a little silly, because the system
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* using this driver is mostly likely a BMC, and hence probably has
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* totally separate fan tachs & pwms of its own that are actually
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* controlling/monitoring the fans -- these are thus unlikely to be
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* doing anything actually useful.
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*/
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data->has_fan = 0x03;
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data->has_fan_min = 0x03;
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data->has_pwm = 0x03;
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/*
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* Because on a BMC this driver may be bound very shortly after power
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* is first applied to the device, the automatic TSI channel detection
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* in nct6775_probe() (which has already been run at this point) may
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* not find anything if a channel hasn't yet produced a temperature
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* reading. Augment whatever was found via autodetection (if
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* anything) with the channels DT says should be active.
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*/
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if (!of_property_read_u32(client->dev.of_node, "nuvoton,tsi-channel-mask",
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&tsi_channel_mask))
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data->have_tsi_temp |= tsi_channel_mask & GENMASK(NUM_TSI_TEMP - 1, 0);
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return 0;
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}
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static const struct regmap_config nct6775_i2c_regmap_config = {
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.reg_bits = 16,
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.val_bits = 16,
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.reg_read = nct6775_i2c_read,
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.reg_write = nct6775_i2c_write,
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};
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static int nct6775_i2c_probe(struct i2c_client *client)
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{
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struct nct6775_data *data;
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const struct of_device_id *of_id;
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const struct i2c_device_id *i2c_id;
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struct device *dev = &client->dev;
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of_id = of_match_device(nct6775_i2c_of_match, dev);
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i2c_id = i2c_match_id(nct6775_i2c_id, client);
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if (of_id && (unsigned long)of_id->data != i2c_id->driver_data)
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dev_notice(dev, "Device mismatch: %s in device tree, %s detected\n",
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of_id->name, i2c_id->name);
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data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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data->kind = i2c_id->driver_data;
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data->read_only = true;
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data->driver_data = client;
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data->driver_init = nct6775_i2c_probe_init;
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return nct6775_probe(dev, data, &nct6775_i2c_regmap_config);
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}
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static struct i2c_driver nct6775_i2c_driver = {
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.class = I2C_CLASS_HWMON,
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.driver = {
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.name = "nct6775-i2c",
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.of_match_table = of_match_ptr(nct6775_i2c_of_match),
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},
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.probe_new = nct6775_i2c_probe,
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.id_table = nct6775_i2c_id,
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};
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module_i2c_driver(nct6775_i2c_driver);
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MODULE_AUTHOR("Zev Weiss <zev@bewilderbeest.net>");
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MODULE_DESCRIPTION("I2C driver for NCT6775F and compatible chips");
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MODULE_LICENSE("GPL");
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MODULE_IMPORT_NS(HWMON_NCT6775);
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