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// SPDX-License-Identifier: GPL-2.0
/*
* nct6775-i2c - I2C driver for the hardware monitoring functionality of
* Nuvoton NCT677x Super-I/O chips
*
* Copyright (C) 2022 Zev Weiss <zev@bewilderbeest.net>
*
* This driver interacts with the chip via it's "back door" i2c interface, as
* is often exposed to a BMC. Because the host may still be operating the
* chip via the ("front door") LPC interface, this driver cannot assume that
* it actually has full control of the chip, and in particular must avoid
* making any changes that could confuse the host's LPC usage of it. It thus
* operates in a strictly read-only fashion, with the only exception being the
* bank-select register (which seems, thankfully, to be replicated for the i2c
* interface so it doesn't affect the LPC interface).
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>
#include <linux/of_device.h>
#include <linux/regmap.h>
#include "nct6775.h"
static int nct6775_i2c_read(void *ctx, unsigned int reg, unsigned int *val)
{
int ret;
u32 tmp;
u8 bank = reg >> 8;
struct nct6775_data *data = ctx;
struct i2c_client *client = data->driver_data;
if (bank != data->bank) {
ret = i2c_smbus_write_byte_data(client, NCT6775_REG_BANK, bank);
if (ret)
return ret;
data->bank = bank;
}
ret = i2c_smbus_read_byte_data(client, reg & 0xff);
if (ret < 0)
return ret;
tmp = ret;
if (nct6775_reg_is_word_sized(data, reg)) {
ret = i2c_smbus_read_byte_data(client, (reg & 0xff) + 1);
if (ret < 0)
return ret;
tmp = (tmp << 8) | ret;
}
*val = tmp;
return 0;
}
/*
* The write operation is a dummy so as not to disturb anything being done
* with the chip via LPC.
*/
static int nct6775_i2c_write(void *ctx, unsigned int reg, unsigned int value)
{
struct nct6775_data *data = ctx;
struct i2c_client *client = data->driver_data;
dev_dbg(&client->dev, "skipping attempted write: %02x -> %03x\n", value, reg);
/*
* This is a lie, but writing anything but the bank-select register is
* something this driver shouldn't be doing.
*/
return 0;
}
static const struct of_device_id __maybe_unused nct6775_i2c_of_match[] = {
{ .compatible = "nuvoton,nct6106", .data = (void *)nct6106, },
{ .compatible = "nuvoton,nct6116", .data = (void *)nct6116, },
{ .compatible = "nuvoton,nct6775", .data = (void *)nct6775, },
{ .compatible = "nuvoton,nct6776", .data = (void *)nct6776, },
{ .compatible = "nuvoton,nct6779", .data = (void *)nct6779, },
{ .compatible = "nuvoton,nct6791", .data = (void *)nct6791, },
{ .compatible = "nuvoton,nct6792", .data = (void *)nct6792, },
{ .compatible = "nuvoton,nct6793", .data = (void *)nct6793, },
{ .compatible = "nuvoton,nct6795", .data = (void *)nct6795, },
{ .compatible = "nuvoton,nct6796", .data = (void *)nct6796, },
{ .compatible = "nuvoton,nct6797", .data = (void *)nct6797, },
{ .compatible = "nuvoton,nct6798", .data = (void *)nct6798, },
{ .compatible = "nuvoton,nct6799", .data = (void *)nct6799, },
{ },
};
MODULE_DEVICE_TABLE(of, nct6775_i2c_of_match);
static const struct i2c_device_id nct6775_i2c_id[] = {
{ "nct6106", nct6106 },
{ "nct6116", nct6116 },
{ "nct6775", nct6775 },
{ "nct6776", nct6776 },
{ "nct6779", nct6779 },
{ "nct6791", nct6791 },
{ "nct6792", nct6792 },
{ "nct6793", nct6793 },
{ "nct6795", nct6795 },
{ "nct6796", nct6796 },
{ "nct6797", nct6797 },
{ "nct6798", nct6798 },
{ "nct6799", nct6799 },
{ }
};
MODULE_DEVICE_TABLE(i2c, nct6775_i2c_id);
static int nct6775_i2c_probe_init(struct nct6775_data *data)
{
u32 tsi_channel_mask;
struct i2c_client *client = data->driver_data;
/*
* The i2c interface doesn't provide access to the control registers
* needed to determine the presence of other fans, but fans 1 and 2
* are (in principle) always there.
*
* In practice this is perhaps a little silly, because the system
* using this driver is mostly likely a BMC, and hence probably has
* totally separate fan tachs & pwms of its own that are actually
* controlling/monitoring the fans -- these are thus unlikely to be
* doing anything actually useful.
*/
data->has_fan = 0x03;
data->has_fan_min = 0x03;
data->has_pwm = 0x03;
/*
* Because on a BMC this driver may be bound very shortly after power
* is first applied to the device, the automatic TSI channel detection
* in nct6775_probe() (which has already been run at this point) may
* not find anything if a channel hasn't yet produced a temperature
* reading. Augment whatever was found via autodetection (if
* anything) with the channels DT says should be active.
*/
if (!of_property_read_u32(client->dev.of_node, "nuvoton,tsi-channel-mask",
&tsi_channel_mask))
data->have_tsi_temp |= tsi_channel_mask & GENMASK(NUM_TSI_TEMP - 1, 0);
return 0;
}
static const struct regmap_config nct6775_i2c_regmap_config = {
.reg_bits = 16,
.val_bits = 16,
.reg_read = nct6775_i2c_read,
.reg_write = nct6775_i2c_write,
};
static int nct6775_i2c_probe(struct i2c_client *client)
{
struct nct6775_data *data;
const struct of_device_id *of_id;
const struct i2c_device_id *i2c_id;
struct device *dev = &client->dev;
of_id = of_match_device(nct6775_i2c_of_match, dev);
i2c_id = i2c_match_id(nct6775_i2c_id, client);
if (of_id && (unsigned long)of_id->data != i2c_id->driver_data)
dev_notice(dev, "Device mismatch: %s in device tree, %s detected\n",
of_id->name, i2c_id->name);
data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->kind = i2c_id->driver_data;
data->read_only = true;
data->driver_data = client;
data->driver_init = nct6775_i2c_probe_init;
return nct6775_probe(dev, data, &nct6775_i2c_regmap_config);
}
static struct i2c_driver nct6775_i2c_driver = {
.class = I2C_CLASS_HWMON,
.driver = {
.name = "nct6775-i2c",
.of_match_table = of_match_ptr(nct6775_i2c_of_match),
},
.probe = nct6775_i2c_probe,
.id_table = nct6775_i2c_id,
};
module_i2c_driver(nct6775_i2c_driver);
MODULE_AUTHOR("Zev Weiss <zev@bewilderbeest.net>");
MODULE_DESCRIPTION("I2C driver for NCT6775F and compatible chips");
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS(HWMON_NCT6775);
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