1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * RTC driver for the interal RTC block in the Amlogic Meson6, Meson8,
4 * Meson8b and Meson8m2 SoCs.
5 *
6 * The RTC is split in to two parts, the AHB front end and a simple serial
7 * connection to the actual registers. This driver manages both parts.
8 *
9 * Copyright (c) 2018 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
10 * Copyright (c) 2015 Ben Dooks <ben.dooks@codethink.co.uk> for Codethink Ltd
11 * Based on origin by Carlo Caione <carlo@endlessm.com>
12 */
13
14 #include <linux/bitfield.h>
15 #include <linux/delay.h>
16 #include <linux/io.h>
17 #include <linux/kernel.h>
18 #include <linux/module.h>
19 #include <linux/nvmem-provider.h>
20 #include <linux/of.h>
21 #include <linux/platform_device.h>
22 #include <linux/regmap.h>
23 #include <linux/regulator/consumer.h>
24 #include <linux/reset.h>
25 #include <linux/rtc.h>
26
27 /* registers accessed from cpu bus */
28 #define RTC_ADDR0 0x00
29 #define RTC_ADDR0_LINE_SCLK BIT(0)
30 #define RTC_ADDR0_LINE_SEN BIT(1)
31 #define RTC_ADDR0_LINE_SDI BIT(2)
32 #define RTC_ADDR0_START_SER BIT(17)
33 #define RTC_ADDR0_WAIT_SER BIT(22)
34 #define RTC_ADDR0_DATA GENMASK(31, 24)
35
36 #define RTC_ADDR1 0x04
37 #define RTC_ADDR1_SDO BIT(0)
38 #define RTC_ADDR1_S_READY BIT(1)
39
40 #define RTC_ADDR2 0x08
41 #define RTC_ADDR3 0x0c
42
43 #define RTC_REG4 0x10
44 #define RTC_REG4_STATIC_VALUE GENMASK(7, 0)
45
46 /* rtc registers accessed via rtc-serial interface */
47 #define RTC_COUNTER (0)
48 #define RTC_SEC_ADJ (2)
49 #define RTC_REGMEM_0 (4)
50 #define RTC_REGMEM_1 (5)
51 #define RTC_REGMEM_2 (6)
52 #define RTC_REGMEM_3 (7)
53
54 #define RTC_ADDR_BITS (3) /* number of address bits to send */
55 #define RTC_DATA_BITS (32) /* number of data bits to tx/rx */
56
57 #define MESON_STATIC_BIAS_CUR (0x5 << 1)
58 #define MESON_STATIC_VOLTAGE (0x3 << 11)
59 #define MESON_STATIC_DEFAULT (MESON_STATIC_BIAS_CUR | MESON_STATIC_VOLTAGE)
60
61 struct meson_rtc {
62 struct device *dev; /* device we bound from */
63 struct reset_control *reset; /* reset source */
64 struct regulator *vdd; /* voltage input */
65 struct regmap *peripheral; /* peripheral registers */
66 struct regmap *serial; /* serial registers */
67 };
68
69 static const struct regmap_config meson_rtc_peripheral_regmap_config = {
70 .name = "peripheral-registers",
71 .reg_bits = 8,
72 .val_bits = 32,
73 .reg_stride = 4,
74 .max_register = RTC_REG4,
75 .fast_io = true,
76 };
77
78 /* RTC front-end serialiser controls */
79
meson_rtc_sclk_pulse(struct meson_rtc * rtc)80 static void meson_rtc_sclk_pulse(struct meson_rtc *rtc)
81 {
82 udelay(5);
83 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SCLK, 0);
84 udelay(5);
85 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SCLK,
86 RTC_ADDR0_LINE_SCLK);
87 }
88
meson_rtc_send_bit(struct meson_rtc * rtc,unsigned int bit)89 static void meson_rtc_send_bit(struct meson_rtc *rtc, unsigned int bit)
90 {
91 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI,
92 bit ? RTC_ADDR0_LINE_SDI : 0);
93 meson_rtc_sclk_pulse(rtc);
94 }
95
meson_rtc_send_bits(struct meson_rtc * rtc,u32 data,unsigned int nr)96 static void meson_rtc_send_bits(struct meson_rtc *rtc, u32 data,
97 unsigned int nr)
98 {
99 u32 bit = 1 << (nr - 1);
100
101 while (bit) {
102 meson_rtc_send_bit(rtc, data & bit);
103 bit >>= 1;
104 }
105 }
106
meson_rtc_set_dir(struct meson_rtc * rtc,u32 mode)107 static void meson_rtc_set_dir(struct meson_rtc *rtc, u32 mode)
108 {
109 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN, 0);
110 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI, 0);
111 meson_rtc_send_bit(rtc, mode);
112 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI, 0);
113 }
114
meson_rtc_get_data(struct meson_rtc * rtc)115 static u32 meson_rtc_get_data(struct meson_rtc *rtc)
116 {
117 u32 tmp, val = 0;
118 int bit;
119
120 for (bit = 0; bit < RTC_DATA_BITS; bit++) {
121 meson_rtc_sclk_pulse(rtc);
122 val <<= 1;
123
124 regmap_read(rtc->peripheral, RTC_ADDR1, &tmp);
125 val |= tmp & RTC_ADDR1_SDO;
126 }
127
128 return val;
129 }
130
meson_rtc_get_bus(struct meson_rtc * rtc)131 static int meson_rtc_get_bus(struct meson_rtc *rtc)
132 {
133 int ret, retries;
134 u32 val;
135
136 /* prepare bus for transfers, set all lines low */
137 val = RTC_ADDR0_LINE_SDI | RTC_ADDR0_LINE_SEN | RTC_ADDR0_LINE_SCLK;
138 regmap_update_bits(rtc->peripheral, RTC_ADDR0, val, 0);
139
140 for (retries = 0; retries < 3; retries++) {
141 /* wait for the bus to be ready */
142 if (!regmap_read_poll_timeout(rtc->peripheral, RTC_ADDR1, val,
143 val & RTC_ADDR1_S_READY, 10,
144 10000))
145 return 0;
146
147 dev_warn(rtc->dev, "failed to get bus, resetting RTC\n");
148
149 ret = reset_control_reset(rtc->reset);
150 if (ret)
151 return ret;
152 }
153
154 dev_err(rtc->dev, "bus is not ready\n");
155 return -ETIMEDOUT;
156 }
157
meson_rtc_serial_bus_reg_read(void * context,unsigned int reg,unsigned int * data)158 static int meson_rtc_serial_bus_reg_read(void *context, unsigned int reg,
159 unsigned int *data)
160 {
161 struct meson_rtc *rtc = context;
162 int ret;
163
164 ret = meson_rtc_get_bus(rtc);
165 if (ret)
166 return ret;
167
168 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN,
169 RTC_ADDR0_LINE_SEN);
170 meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
171 meson_rtc_set_dir(rtc, 0);
172 *data = meson_rtc_get_data(rtc);
173
174 return 0;
175 }
176
meson_rtc_serial_bus_reg_write(void * context,unsigned int reg,unsigned int data)177 static int meson_rtc_serial_bus_reg_write(void *context, unsigned int reg,
178 unsigned int data)
179 {
180 struct meson_rtc *rtc = context;
181 int ret;
182
183 ret = meson_rtc_get_bus(rtc);
184 if (ret)
185 return ret;
186
187 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN,
188 RTC_ADDR0_LINE_SEN);
189 meson_rtc_send_bits(rtc, data, RTC_DATA_BITS);
190 meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
191 meson_rtc_set_dir(rtc, 1);
192
193 return 0;
194 }
195
196 static const struct regmap_bus meson_rtc_serial_bus = {
197 .reg_read = meson_rtc_serial_bus_reg_read,
198 .reg_write = meson_rtc_serial_bus_reg_write,
199 };
200
201 static const struct regmap_config meson_rtc_serial_regmap_config = {
202 .name = "serial-registers",
203 .reg_bits = 4,
204 .reg_stride = 1,
205 .val_bits = 32,
206 .max_register = RTC_REGMEM_3,
207 .fast_io = false,
208 };
209
meson_rtc_write_static(struct meson_rtc * rtc,u32 data)210 static int meson_rtc_write_static(struct meson_rtc *rtc, u32 data)
211 {
212 u32 tmp;
213
214 regmap_write(rtc->peripheral, RTC_REG4,
215 FIELD_PREP(RTC_REG4_STATIC_VALUE, (data >> 8)));
216
217 /* write the static value and start the auto serializer */
218 tmp = FIELD_PREP(RTC_ADDR0_DATA, (data & 0xff)) | RTC_ADDR0_START_SER;
219 regmap_update_bits(rtc->peripheral, RTC_ADDR0,
220 RTC_ADDR0_DATA | RTC_ADDR0_START_SER, tmp);
221
222 /* wait for the auto serializer to complete */
223 return regmap_read_poll_timeout(rtc->peripheral, RTC_REG4, tmp,
224 !(tmp & RTC_ADDR0_WAIT_SER), 10,
225 10000);
226 }
227
228 /* RTC interface layer functions */
229
meson_rtc_gettime(struct device * dev,struct rtc_time * tm)230 static int meson_rtc_gettime(struct device *dev, struct rtc_time *tm)
231 {
232 struct meson_rtc *rtc = dev_get_drvdata(dev);
233 u32 time;
234 int ret;
235
236 ret = regmap_read(rtc->serial, RTC_COUNTER, &time);
237 if (!ret)
238 rtc_time64_to_tm(time, tm);
239
240 return ret;
241 }
242
meson_rtc_settime(struct device * dev,struct rtc_time * tm)243 static int meson_rtc_settime(struct device *dev, struct rtc_time *tm)
244 {
245 struct meson_rtc *rtc = dev_get_drvdata(dev);
246
247 return regmap_write(rtc->serial, RTC_COUNTER, rtc_tm_to_time64(tm));
248 }
249
250 static const struct rtc_class_ops meson_rtc_ops = {
251 .read_time = meson_rtc_gettime,
252 .set_time = meson_rtc_settime,
253 };
254
255 /* NVMEM interface layer functions */
256
meson_rtc_regmem_read(void * context,unsigned int offset,void * buf,size_t bytes)257 static int meson_rtc_regmem_read(void *context, unsigned int offset,
258 void *buf, size_t bytes)
259 {
260 struct meson_rtc *rtc = context;
261 unsigned int read_offset, read_size;
262
263 read_offset = RTC_REGMEM_0 + (offset / 4);
264 read_size = bytes / 4;
265
266 return regmap_bulk_read(rtc->serial, read_offset, buf, read_size);
267 }
268
meson_rtc_regmem_write(void * context,unsigned int offset,void * buf,size_t bytes)269 static int meson_rtc_regmem_write(void *context, unsigned int offset,
270 void *buf, size_t bytes)
271 {
272 struct meson_rtc *rtc = context;
273 unsigned int write_offset, write_size;
274
275 write_offset = RTC_REGMEM_0 + (offset / 4);
276 write_size = bytes / 4;
277
278 return regmap_bulk_write(rtc->serial, write_offset, buf, write_size);
279 }
280
meson_rtc_probe(struct platform_device * pdev)281 static int meson_rtc_probe(struct platform_device *pdev)
282 {
283 struct nvmem_config meson_rtc_nvmem_config = {
284 .name = "meson-rtc-regmem",
285 .type = NVMEM_TYPE_BATTERY_BACKED,
286 .word_size = 4,
287 .stride = 4,
288 .size = 4 * 4,
289 .reg_read = meson_rtc_regmem_read,
290 .reg_write = meson_rtc_regmem_write,
291 };
292 struct device *dev = &pdev->dev;
293 struct meson_rtc *rtc;
294 struct rtc_device *rtc_dev;
295 void __iomem *base;
296 int ret;
297 u32 tm;
298
299 rtc = devm_kzalloc(dev, sizeof(struct meson_rtc), GFP_KERNEL);
300 if (!rtc)
301 return -ENOMEM;
302
303 rtc_dev = devm_rtc_allocate_device(dev);
304 if (IS_ERR(rtc_dev))
305 return PTR_ERR(rtc_dev);
306
307 platform_set_drvdata(pdev, rtc);
308
309 rtc->dev = dev;
310
311 rtc_dev->ops = &meson_rtc_ops;
312 rtc_dev->range_max = U32_MAX;
313
314 base = devm_platform_ioremap_resource(pdev, 0);
315 if (IS_ERR(base))
316 return PTR_ERR(base);
317
318 rtc->peripheral = devm_regmap_init_mmio(dev, base,
319 &meson_rtc_peripheral_regmap_config);
320 if (IS_ERR(rtc->peripheral)) {
321 dev_err(dev, "failed to create peripheral regmap\n");
322 return PTR_ERR(rtc->peripheral);
323 }
324
325 rtc->reset = devm_reset_control_get(dev, NULL);
326 if (IS_ERR(rtc->reset)) {
327 dev_err(dev, "missing reset line\n");
328 return PTR_ERR(rtc->reset);
329 }
330
331 rtc->vdd = devm_regulator_get(dev, "vdd");
332 if (IS_ERR(rtc->vdd)) {
333 dev_err(dev, "failed to get the vdd-supply\n");
334 return PTR_ERR(rtc->vdd);
335 }
336
337 ret = regulator_enable(rtc->vdd);
338 if (ret) {
339 dev_err(dev, "failed to enable vdd-supply\n");
340 return ret;
341 }
342
343 ret = meson_rtc_write_static(rtc, MESON_STATIC_DEFAULT);
344 if (ret) {
345 dev_err(dev, "failed to set static values\n");
346 goto out_disable_vdd;
347 }
348
349 rtc->serial = devm_regmap_init(dev, &meson_rtc_serial_bus, rtc,
350 &meson_rtc_serial_regmap_config);
351 if (IS_ERR(rtc->serial)) {
352 dev_err(dev, "failed to create serial regmap\n");
353 ret = PTR_ERR(rtc->serial);
354 goto out_disable_vdd;
355 }
356
357 /*
358 * check if we can read RTC counter, if not then the RTC is probably
359 * not functional. If it isn't probably best to not bind.
360 */
361 ret = regmap_read(rtc->serial, RTC_COUNTER, &tm);
362 if (ret) {
363 dev_err(dev, "cannot read RTC counter, RTC not functional\n");
364 goto out_disable_vdd;
365 }
366
367 meson_rtc_nvmem_config.priv = rtc;
368 ret = devm_rtc_nvmem_register(rtc_dev, &meson_rtc_nvmem_config);
369 if (ret)
370 goto out_disable_vdd;
371
372 ret = devm_rtc_register_device(rtc_dev);
373 if (ret)
374 goto out_disable_vdd;
375
376 return 0;
377
378 out_disable_vdd:
379 regulator_disable(rtc->vdd);
380 return ret;
381 }
382
383 static const __maybe_unused struct of_device_id meson_rtc_dt_match[] = {
384 { .compatible = "amlogic,meson6-rtc", },
385 { .compatible = "amlogic,meson8-rtc", },
386 { .compatible = "amlogic,meson8b-rtc", },
387 { .compatible = "amlogic,meson8m2-rtc", },
388 { },
389 };
390 MODULE_DEVICE_TABLE(of, meson_rtc_dt_match);
391
392 static struct platform_driver meson_rtc_driver = {
393 .probe = meson_rtc_probe,
394 .driver = {
395 .name = "meson-rtc",
396 .of_match_table = of_match_ptr(meson_rtc_dt_match),
397 },
398 };
399 module_platform_driver(meson_rtc_driver);
400
401 MODULE_DESCRIPTION("Amlogic Meson RTC Driver");
402 MODULE_AUTHOR("Ben Dooks <ben.dooks@codethink.co.uk>");
403 MODULE_AUTHOR("Martin Blumenstingl <martin.blumenstingl@googlemail.com>");
404 MODULE_LICENSE("GPL v2");
405 MODULE_ALIAS("platform:meson-rtc");
406