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1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* | |
3 | * nct6775-i2c - I2C driver for the hardware monitoring functionality of | |
4 | * Nuvoton NCT677x Super-I/O chips | |
5 | * | |
6 | * Copyright (C) 2022 Zev Weiss <zev@bewilderbeest.net> | |
7 | * | |
8 | * This driver interacts with the chip via it's "back door" i2c interface, as | |
9 | * is often exposed to a BMC. Because the host may still be operating the | |
10 | * chip via the ("front door") LPC interface, this driver cannot assume that | |
11 | * it actually has full control of the chip, and in particular must avoid | |
12 | * making any changes that could confuse the host's LPC usage of it. It thus | |
13 | * operates in a strictly read-only fashion, with the only exception being the | |
14 | * bank-select register (which seems, thankfully, to be replicated for the i2c | |
15 | * interface so it doesn't affect the LPC interface). | |
16 | */ | |
17 | ||
18 | #include <linux/module.h> | |
19 | #include <linux/init.h> | |
20 | #include <linux/i2c.h> | |
21 | #include <linux/hwmon.h> | |
22 | #include <linux/hwmon-sysfs.h> | |
23 | #include <linux/err.h> | |
24 | #include <linux/of_device.h> | |
25 | #include <linux/regmap.h> | |
26 | #include "nct6775.h" | |
27 | ||
28 | static int nct6775_i2c_read(void *ctx, unsigned int reg, unsigned int *val) | |
29 | { | |
30 | int ret; | |
31 | u32 tmp; | |
32 | u8 bank = reg >> 8; | |
33 | struct nct6775_data *data = ctx; | |
34 | struct i2c_client *client = data->driver_data; | |
35 | ||
36 | if (bank != data->bank) { | |
37 | ret = i2c_smbus_write_byte_data(client, NCT6775_REG_BANK, bank); | |
38 | if (ret) | |
39 | return ret; | |
40 | data->bank = bank; | |
41 | } | |
42 | ||
43 | ret = i2c_smbus_read_byte_data(client, reg & 0xff); | |
44 | if (ret < 0) | |
45 | return ret; | |
46 | tmp = ret; | |
47 | ||
48 | if (nct6775_reg_is_word_sized(data, reg)) { | |
49 | ret = i2c_smbus_read_byte_data(client, (reg & 0xff) + 1); | |
50 | if (ret < 0) | |
51 | return ret; | |
52 | tmp = (tmp << 8) | ret; | |
53 | } | |
54 | ||
55 | *val = tmp; | |
56 | return 0; | |
57 | } | |
58 | ||
59 | /* | |
60 | * The write operation is a dummy so as not to disturb anything being done | |
61 | * with the chip via LPC. | |
62 | */ | |
63 | static int nct6775_i2c_write(void *ctx, unsigned int reg, unsigned int value) | |
64 | { | |
65 | struct nct6775_data *data = ctx; | |
66 | struct i2c_client *client = data->driver_data; | |
67 | ||
68 | dev_dbg(&client->dev, "skipping attempted write: %02x -> %03x\n", value, reg); | |
69 | ||
70 | /* | |
71 | * This is a lie, but writing anything but the bank-select register is | |
72 | * something this driver shouldn't be doing. | |
73 | */ | |
74 | return 0; | |
75 | } | |
76 | ||
77 | static const struct of_device_id __maybe_unused nct6775_i2c_of_match[] = { | |
78 | { .compatible = "nuvoton,nct6106", .data = (void *)nct6106, }, | |
79 | { .compatible = "nuvoton,nct6116", .data = (void *)nct6116, }, | |
80 | { .compatible = "nuvoton,nct6775", .data = (void *)nct6775, }, | |
81 | { .compatible = "nuvoton,nct6776", .data = (void *)nct6776, }, | |
82 | { .compatible = "nuvoton,nct6779", .data = (void *)nct6779, }, | |
83 | { .compatible = "nuvoton,nct6791", .data = (void *)nct6791, }, | |
84 | { .compatible = "nuvoton,nct6792", .data = (void *)nct6792, }, | |
85 | { .compatible = "nuvoton,nct6793", .data = (void *)nct6793, }, | |
86 | { .compatible = "nuvoton,nct6795", .data = (void *)nct6795, }, | |
87 | { .compatible = "nuvoton,nct6796", .data = (void *)nct6796, }, | |
88 | { .compatible = "nuvoton,nct6797", .data = (void *)nct6797, }, | |
89 | { .compatible = "nuvoton,nct6798", .data = (void *)nct6798, }, | |
90 | { }, | |
91 | }; | |
92 | MODULE_DEVICE_TABLE(of, nct6775_i2c_of_match); | |
93 | ||
94 | static const struct i2c_device_id nct6775_i2c_id[] = { | |
95 | { "nct6106", nct6106 }, | |
96 | { "nct6116", nct6116 }, | |
97 | { "nct6775", nct6775 }, | |
98 | { "nct6776", nct6776 }, | |
99 | { "nct6779", nct6779 }, | |
100 | { "nct6791", nct6791 }, | |
101 | { "nct6792", nct6792 }, | |
102 | { "nct6793", nct6793 }, | |
103 | { "nct6795", nct6795 }, | |
104 | { "nct6796", nct6796 }, | |
105 | { "nct6797", nct6797 }, | |
106 | { "nct6798", nct6798 }, | |
107 | { } | |
108 | }; | |
109 | MODULE_DEVICE_TABLE(i2c, nct6775_i2c_id); | |
110 | ||
111 | static int nct6775_i2c_probe_init(struct nct6775_data *data) | |
112 | { | |
113 | u32 tsi_channel_mask; | |
114 | struct i2c_client *client = data->driver_data; | |
115 | ||
116 | /* | |
117 | * The i2c interface doesn't provide access to the control registers | |
118 | * needed to determine the presence of other fans, but fans 1 and 2 | |
119 | * are (in principle) always there. | |
120 | * | |
121 | * In practice this is perhaps a little silly, because the system | |
122 | * using this driver is mostly likely a BMC, and hence probably has | |
123 | * totally separate fan tachs & pwms of its own that are actually | |
124 | * controlling/monitoring the fans -- these are thus unlikely to be | |
125 | * doing anything actually useful. | |
126 | */ | |
127 | data->has_fan = 0x03; | |
128 | data->has_fan_min = 0x03; | |
129 | data->has_pwm = 0x03; | |
130 | ||
131 | /* | |
132 | * Because on a BMC this driver may be bound very shortly after power | |
133 | * is first applied to the device, the automatic TSI channel detection | |
134 | * in nct6775_probe() (which has already been run at this point) may | |
135 | * not find anything if a channel hasn't yet produced a temperature | |
136 | * reading. Augment whatever was found via autodetection (if | |
137 | * anything) with the channels DT says should be active. | |
138 | */ | |
139 | if (!of_property_read_u32(client->dev.of_node, "nuvoton,tsi-channel-mask", | |
140 | &tsi_channel_mask)) | |
141 | data->have_tsi_temp |= tsi_channel_mask & GENMASK(NUM_TSI_TEMP - 1, 0); | |
142 | ||
143 | return 0; | |
144 | } | |
145 | ||
146 | static const struct regmap_config nct6775_i2c_regmap_config = { | |
147 | .reg_bits = 16, | |
148 | .val_bits = 16, | |
149 | .reg_read = nct6775_i2c_read, | |
150 | .reg_write = nct6775_i2c_write, | |
151 | }; | |
152 | ||
153 | static int nct6775_i2c_probe(struct i2c_client *client) | |
154 | { | |
155 | struct nct6775_data *data; | |
156 | const struct of_device_id *of_id; | |
157 | const struct i2c_device_id *i2c_id; | |
158 | struct device *dev = &client->dev; | |
159 | ||
160 | of_id = of_match_device(nct6775_i2c_of_match, dev); | |
161 | i2c_id = i2c_match_id(nct6775_i2c_id, client); | |
162 | ||
163 | if (of_id && (unsigned long)of_id->data != i2c_id->driver_data) | |
164 | dev_notice(dev, "Device mismatch: %s in device tree, %s detected\n", | |
165 | of_id->name, i2c_id->name); | |
166 | ||
167 | data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL); | |
168 | if (!data) | |
169 | return -ENOMEM; | |
170 | ||
171 | data->kind = i2c_id->driver_data; | |
172 | ||
173 | data->read_only = true; | |
174 | data->driver_data = client; | |
175 | data->driver_init = nct6775_i2c_probe_init; | |
176 | ||
177 | return nct6775_probe(dev, data, &nct6775_i2c_regmap_config); | |
178 | } | |
179 | ||
180 | static struct i2c_driver nct6775_i2c_driver = { | |
181 | .class = I2C_CLASS_HWMON, | |
182 | .driver = { | |
183 | .name = "nct6775-i2c", | |
184 | .of_match_table = of_match_ptr(nct6775_i2c_of_match), | |
185 | }, | |
186 | .probe_new = nct6775_i2c_probe, | |
187 | .id_table = nct6775_i2c_id, | |
188 | }; | |
189 | ||
190 | module_i2c_driver(nct6775_i2c_driver); | |
191 | ||
192 | MODULE_AUTHOR("Zev Weiss <zev@bewilderbeest.net>"); | |
193 | MODULE_DESCRIPTION("I2C driver for NCT6775F and compatible chips"); | |
194 | MODULE_LICENSE("GPL"); | |
195 | MODULE_IMPORT_NS(HWMON_NCT6775); |