diff options
Diffstat (limited to 'drivers/hwmon/nct6775-i2c.c')
| -rw-r--r-- | drivers/hwmon/nct6775-i2c.c | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/drivers/hwmon/nct6775-i2c.c b/drivers/hwmon/nct6775-i2c.c new file mode 100644 index 000000000..e1bcd1146 --- /dev/null +++ b/drivers/hwmon/nct6775-i2c.c @@ -0,0 +1,195 @@ +// 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, }, + { }, +}; +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 }, + { } +}; +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_new = 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); |