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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
61struct meson_rtc {
62 struct rtc_device *rtc; /* rtc device we created */
63 struct device *dev; /* device we bound from */
64 struct reset_control *reset; /* reset source */
65 struct regulator *vdd; /* voltage input */
66 struct regmap *peripheral; /* peripheral registers */
67 struct regmap *serial; /* serial registers */
68};
69
70static const struct regmap_config meson_rtc_peripheral_regmap_config = {
71 .name = "peripheral-registers",
72 .reg_bits = 8,
73 .val_bits = 32,
74 .reg_stride = 4,
75 .max_register = RTC_REG4,
76 .fast_io = true,
77};
78
79/* RTC front-end serialiser controls */
80
81static void meson_rtc_sclk_pulse(struct meson_rtc *rtc)
82{
83 udelay(5);
84 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SCLK, 0);
85 udelay(5);
86 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SCLK,
87 RTC_ADDR0_LINE_SCLK);
88}
89
90static void meson_rtc_send_bit(struct meson_rtc *rtc, unsigned int bit)
91{
92 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI,
93 bit ? RTC_ADDR0_LINE_SDI : 0);
94 meson_rtc_sclk_pulse(rtc);
95}
96
97static void meson_rtc_send_bits(struct meson_rtc *rtc, u32 data,
98 unsigned int nr)
99{
100 u32 bit = 1 << (nr - 1);
101
102 while (bit) {
103 meson_rtc_send_bit(rtc, data & bit);
104 bit >>= 1;
105 }
106}
107
108static void meson_rtc_set_dir(struct meson_rtc *rtc, u32 mode)
109{
110 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN, 0);
111 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI, 0);
112 meson_rtc_send_bit(rtc, mode);
113 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI, 0);
114}
115
116static u32 meson_rtc_get_data(struct meson_rtc *rtc)
117{
118 u32 tmp, val = 0;
119 int bit;
120
121 for (bit = 0; bit < RTC_DATA_BITS; bit++) {
122 meson_rtc_sclk_pulse(rtc);
123 val <<= 1;
124
125 regmap_read(rtc->peripheral, RTC_ADDR1, &tmp);
126 val |= tmp & RTC_ADDR1_SDO;
127 }
128
129 return val;
130}
131
132static int meson_rtc_get_bus(struct meson_rtc *rtc)
133{
134 int ret, retries = 3;
135 u32 val;
136
137 /* prepare bus for transfers, set all lines low */
138 val = RTC_ADDR0_LINE_SDI | RTC_ADDR0_LINE_SEN | RTC_ADDR0_LINE_SCLK;
139 regmap_update_bits(rtc->peripheral, RTC_ADDR0, val, 0);
140
141 for (retries = 0; retries < 3; retries++) {
142 /* wait for the bus to be ready */
143 if (!regmap_read_poll_timeout(rtc->peripheral, RTC_ADDR1, val,
144 val & RTC_ADDR1_S_READY, 10,
145 10000))
146 return 0;
147
148 dev_warn(rtc->dev, "failed to get bus, resetting RTC\n");
149
150 ret = reset_control_reset(rtc->reset);
151 if (ret)
152 return ret;
153 }
154
155 dev_err(rtc->dev, "bus is not ready\n");
156 return -ETIMEDOUT;
157}
158
159static int meson_rtc_serial_bus_reg_read(void *context, unsigned int reg,
160 unsigned int *data)
161{
162 struct meson_rtc *rtc = context;
163 int ret;
164
165 ret = meson_rtc_get_bus(rtc);
166 if (ret)
167 return ret;
168
169 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN,
170 RTC_ADDR0_LINE_SEN);
171 meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
172 meson_rtc_set_dir(rtc, 0);
173 *data = meson_rtc_get_data(rtc);
174
175 return 0;
176}
177
178static int meson_rtc_serial_bus_reg_write(void *context, unsigned int reg,
179 unsigned int data)
180{
181 struct meson_rtc *rtc = context;
182 int ret;
183
184 ret = meson_rtc_get_bus(rtc);
185 if (ret)
186 return ret;
187
188 regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN,
189 RTC_ADDR0_LINE_SEN);
190 meson_rtc_send_bits(rtc, data, RTC_DATA_BITS);
191 meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
192 meson_rtc_set_dir(rtc, 1);
193
194 return 0;
195}
196
197static const struct regmap_bus meson_rtc_serial_bus = {
198 .reg_read = meson_rtc_serial_bus_reg_read,
199 .reg_write = meson_rtc_serial_bus_reg_write,
200};
201
202static const struct regmap_config meson_rtc_serial_regmap_config = {
203 .name = "serial-registers",
204 .reg_bits = 4,
205 .reg_stride = 1,
206 .val_bits = 32,
207 .max_register = RTC_REGMEM_3,
208 .fast_io = false,
209};
210
211static int meson_rtc_write_static(struct meson_rtc *rtc, u32 data)
212{
213 u32 tmp;
214
215 regmap_write(rtc->peripheral, RTC_REG4,
216 FIELD_PREP(RTC_REG4_STATIC_VALUE, (data >> 8)));
217
218 /* write the static value and start the auto serializer */
219 tmp = FIELD_PREP(RTC_ADDR0_DATA, (data & 0xff)) | RTC_ADDR0_START_SER;
220 regmap_update_bits(rtc->peripheral, RTC_ADDR0,
221 RTC_ADDR0_DATA | RTC_ADDR0_START_SER, tmp);
222
223 /* wait for the auto serializer to complete */
224 return regmap_read_poll_timeout(rtc->peripheral, RTC_REG4, tmp,
225 !(tmp & RTC_ADDR0_WAIT_SER), 10,
226 10000);
227}
228
229/* RTC interface layer functions */
230
231static int meson_rtc_gettime(struct device *dev, struct rtc_time *tm)
232{
233 struct meson_rtc *rtc = dev_get_drvdata(dev);
234 u32 time;
235 int ret;
236
237 ret = regmap_read(rtc->serial, RTC_COUNTER, &time);
238 if (!ret)
239 rtc_time64_to_tm(time, tm);
240
241 return ret;
242}
243
244static int meson_rtc_settime(struct device *dev, struct rtc_time *tm)
245{
246 struct meson_rtc *rtc = dev_get_drvdata(dev);
247
248 return regmap_write(rtc->serial, RTC_COUNTER, rtc_tm_to_time64(tm));
249}
250
251static const struct rtc_class_ops meson_rtc_ops = {
252 .read_time = meson_rtc_gettime,
253 .set_time = meson_rtc_settime,
254};
255
256/* NVMEM interface layer functions */
257
258static int meson_rtc_regmem_read(void *context, unsigned int offset,
259 void *buf, size_t bytes)
260{
261 struct meson_rtc *rtc = context;
262 unsigned int read_offset, read_size;
263
264 read_offset = RTC_REGMEM_0 + (offset / 4);
265 read_size = bytes / 4;
266
267 return regmap_bulk_read(rtc->serial, read_offset, buf, read_size);
268}
269
270static int meson_rtc_regmem_write(void *context, unsigned int offset,
271 void *buf, size_t bytes)
272{
273 struct meson_rtc *rtc = context;
274 unsigned int write_offset, write_size;
275
276 write_offset = RTC_REGMEM_0 + (offset / 4);
277 write_size = bytes / 4;
278
279 return regmap_bulk_write(rtc->serial, write_offset, buf, write_size);
280}
281
282static int meson_rtc_probe(struct platform_device *pdev)
283{
284 struct nvmem_config meson_rtc_nvmem_config = {
285 .name = "meson-rtc-regmem",
286 .type = NVMEM_TYPE_BATTERY_BACKED,
287 .word_size = 4,
288 .stride = 4,
289 .size = 4 * 4,
290 .reg_read = meson_rtc_regmem_read,
291 .reg_write = meson_rtc_regmem_write,
292 };
293 struct device *dev = &pdev->dev;
294 struct meson_rtc *rtc;
295 struct resource *res;
296 void __iomem *base;
297 int ret;
298 u32 tm;
299
300 rtc = devm_kzalloc(dev, sizeof(struct meson_rtc), GFP_KERNEL);
301 if (!rtc)
302 return -ENOMEM;
303
304 rtc->rtc = devm_rtc_allocate_device(dev);
305 if (IS_ERR(rtc->rtc))
306 return PTR_ERR(rtc->rtc);
307
308 platform_set_drvdata(pdev, rtc);
309
310 rtc->dev = dev;
311
312 rtc->rtc->ops = &meson_rtc_ops;
313 rtc->rtc->range_max = U32_MAX;
314
315 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
316 base = devm_ioremap_resource(dev, res);
317 if (IS_ERR(base))
318 return PTR_ERR(base);
319
320 rtc->peripheral = devm_regmap_init_mmio(dev, base,
321 &meson_rtc_peripheral_regmap_config);
322 if (IS_ERR(rtc->peripheral)) {
323 dev_err(dev, "failed to create peripheral regmap\n");
324 return PTR_ERR(rtc->peripheral);
325 }
326
327 rtc->reset = devm_reset_control_get(dev, NULL);
328 if (IS_ERR(rtc->reset)) {
329 dev_err(dev, "missing reset line\n");
330 return PTR_ERR(rtc->reset);
331 }
332
333 rtc->vdd = devm_regulator_get(dev, "vdd");
334 if (IS_ERR(rtc->vdd)) {
335 dev_err(dev, "failed to get the vdd-supply\n");
336 return PTR_ERR(rtc->vdd);
337 }
338
339 ret = regulator_enable(rtc->vdd);
340 if (ret) {
341 dev_err(dev, "failed to enable vdd-supply\n");
342 return ret;
343 }
344
345 ret = meson_rtc_write_static(rtc, MESON_STATIC_DEFAULT);
346 if (ret) {
347 dev_err(dev, "failed to set static values\n");
348 goto out_disable_vdd;
349 }
350
351 rtc->serial = devm_regmap_init(dev, &meson_rtc_serial_bus, rtc,
352 &meson_rtc_serial_regmap_config);
353 if (IS_ERR(rtc->serial)) {
354 dev_err(dev, "failed to create serial regmap\n");
355 ret = PTR_ERR(rtc->serial);
356 goto out_disable_vdd;
357 }
358
359 /*
360 * check if we can read RTC counter, if not then the RTC is probably
361 * not functional. If it isn't probably best to not bind.
362 */
363 ret = regmap_read(rtc->serial, RTC_COUNTER, &tm);
364 if (ret) {
365 dev_err(dev, "cannot read RTC counter, RTC not functional\n");
366 goto out_disable_vdd;
367 }
368
369 meson_rtc_nvmem_config.priv = rtc;
370 ret = rtc_nvmem_register(rtc->rtc, &meson_rtc_nvmem_config);
371 if (ret)
372 goto out_disable_vdd;
373
374 ret = rtc_register_device(rtc->rtc);
375 if (ret)
376 goto out_disable_vdd;
377
378 return 0;
379
380out_disable_vdd:
381 regulator_disable(rtc->vdd);
382 return ret;
383}
384
385static const struct of_device_id meson_rtc_dt_match[] = {
386 { .compatible = "amlogic,meson6-rtc", },
387 { .compatible = "amlogic,meson8-rtc", },
388 { .compatible = "amlogic,meson8b-rtc", },
389 { .compatible = "amlogic,meson8m2-rtc", },
390 { },
391};
392MODULE_DEVICE_TABLE(of, meson_rtc_dt_match);
393
394static struct platform_driver meson_rtc_driver = {
395 .probe = meson_rtc_probe,
396 .driver = {
397 .name = "meson-rtc",
398 .of_match_table = of_match_ptr(meson_rtc_dt_match),
399 },
400};
401module_platform_driver(meson_rtc_driver);
402
403MODULE_DESCRIPTION("Amlogic Meson RTC Driver");
404MODULE_AUTHOR("Ben Dooks <ben.doosk@codethink.co.uk>");
405MODULE_AUTHOR("Martin Blumenstingl <martin.blumenstingl@googlemail.com>");
406MODULE_LICENSE("GPL v2");
407MODULE_ALIAS("platform:meson-rtc");