1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Delta AHE-50DC power shelf fan control module driver
  4 *
  5 * Copyright 2021 Zev Weiss <zev@bewilderbeest.net>
  6 */
  7
  8#include <linux/i2c.h>
  9#include <linux/kernel.h>
 10#include <linux/module.h>
 11#include <linux/pmbus.h>
 12
 13#include "pmbus.h"
 14
 15#define AHE50DC_PMBUS_READ_TEMP4 0xd0
 16
 17static int ahe50dc_fan_write_byte(struct i2c_client *client, int page, u8 value)
 18{
 19	/*
 20	 * The CLEAR_FAULTS operation seems to sometimes (unpredictably, perhaps
 21	 * 5% of the time or so) trigger a problematic phenomenon in which the
 22	 * fan speeds surge momentarily and at least some (perhaps all?) of the
 23	 * system's power outputs experience a glitch.
 24	 *
 25	 * However, according to Delta it should be OK to simply not send any
 26	 * CLEAR_FAULTS commands (the device doesn't seem to be capable of
 27	 * reporting any faults anyway), so just blackhole them unconditionally.
 28	 */
 29	return value == PMBUS_CLEAR_FAULTS ? -EOPNOTSUPP : -ENODATA;
 30}
 31
 32static int ahe50dc_fan_read_word_data(struct i2c_client *client, int page, int phase, int reg)
 33{
 34	/* temp1 in (virtual) page 1 is remapped to mfr-specific temp4 */
 35	if (page == 1) {
 36		if (reg == PMBUS_READ_TEMPERATURE_1)
 37			return i2c_smbus_read_word_data(client, AHE50DC_PMBUS_READ_TEMP4);
 38		return -EOPNOTSUPP;
 39	}
 40
 41	/*
 42	 * There's a fairly limited set of commands this device actually
 43	 * supports, so here we block attempts to read anything else (which
 44	 * return 0xffff and would cause confusion elsewhere).
 45	 */
 46	switch (reg) {
 47	case PMBUS_STATUS_WORD:
 48	case PMBUS_FAN_COMMAND_1:
 49	case PMBUS_FAN_COMMAND_2:
 50	case PMBUS_FAN_COMMAND_3:
 51	case PMBUS_FAN_COMMAND_4:
 52	case PMBUS_STATUS_FAN_12:
 53	case PMBUS_STATUS_FAN_34:
 54	case PMBUS_READ_VIN:
 55	case PMBUS_READ_TEMPERATURE_1:
 56	case PMBUS_READ_TEMPERATURE_2:
 57	case PMBUS_READ_TEMPERATURE_3:
 58	case PMBUS_READ_FAN_SPEED_1:
 59	case PMBUS_READ_FAN_SPEED_2:
 60	case PMBUS_READ_FAN_SPEED_3:
 61	case PMBUS_READ_FAN_SPEED_4:
 62		return -ENODATA;
 63	default:
 64		return -EOPNOTSUPP;
 65	}
 66}
 67
 68static struct pmbus_driver_info ahe50dc_fan_info = {
 69	.pages = 2,
 70	.format[PSC_FAN] = direct,
 71	.format[PSC_TEMPERATURE] = direct,
 72	.format[PSC_VOLTAGE_IN] = direct,
 73	.m[PSC_FAN] = 1,
 74	.b[PSC_FAN] = 0,
 75	.R[PSC_FAN] = 0,
 76	.m[PSC_TEMPERATURE] = 1,
 77	.b[PSC_TEMPERATURE] = 0,
 78	.R[PSC_TEMPERATURE] = 1,
 79	.m[PSC_VOLTAGE_IN] = 1,
 80	.b[PSC_VOLTAGE_IN] = 0,
 81	.R[PSC_VOLTAGE_IN] = 3,
 82	.func[0] = PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 | PMBUS_HAVE_TEMP3 |
 83		PMBUS_HAVE_VIN | PMBUS_HAVE_FAN12 | PMBUS_HAVE_FAN34 |
 84		PMBUS_HAVE_STATUS_FAN12 | PMBUS_HAVE_STATUS_FAN34 | PMBUS_PAGE_VIRTUAL,
 85	.func[1] = PMBUS_HAVE_TEMP | PMBUS_PAGE_VIRTUAL,
 86	.write_byte = ahe50dc_fan_write_byte,
 87	.read_word_data = ahe50dc_fan_read_word_data,
 88};
 89
 90/*
 91 * CAPABILITY returns 0xff, which appears to be this device's way indicating
 92 * it doesn't support something (and if we enable I2C_CLIENT_PEC on seeing bit
 93 * 7 being set it generates bad PECs, so let's not go there).
 94 */
 95static struct pmbus_platform_data ahe50dc_fan_data = {
 96	.flags = PMBUS_NO_CAPABILITY,
 97};
 98
 99static int ahe50dc_fan_probe(struct i2c_client *client)
100{
101	client->dev.platform_data = &ahe50dc_fan_data;
102	return pmbus_do_probe(client, &ahe50dc_fan_info);
103}
104
105static const struct i2c_device_id ahe50dc_fan_id[] = {
106	{ "ahe50dc_fan" },
107	{ }
108};
109MODULE_DEVICE_TABLE(i2c, ahe50dc_fan_id);
110
111static const struct of_device_id __maybe_unused ahe50dc_fan_of_match[] = {
112	{ .compatible = "delta,ahe50dc-fan" },
113	{ }
114};
115MODULE_DEVICE_TABLE(of, ahe50dc_fan_of_match);
116
117static struct i2c_driver ahe50dc_fan_driver = {
118	.driver = {
119		   .name = "ahe50dc_fan",
120		   .of_match_table = of_match_ptr(ahe50dc_fan_of_match),
121	},
122	.probe = ahe50dc_fan_probe,
123	.id_table = ahe50dc_fan_id,
124};
125module_i2c_driver(ahe50dc_fan_driver);
126
127MODULE_AUTHOR("Zev Weiss <zev@bewilderbeest.net>");
128MODULE_DESCRIPTION("Driver for Delta AHE-50DC power shelf fan control module");
129MODULE_LICENSE("GPL");
130MODULE_IMPORT_NS(PMBUS);