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1// SPDX-License-Identifier: (GPL-2.0 OR MIT)
2/*
3 * SPI core driver for the Ocelot chip family.
4 *
5 * This driver will handle everything necessary to allow for communication over
6 * SPI to the VSC7511, VSC7512, VSC7513 and VSC7514 chips. The main functions
7 * are to prepare the chip's SPI interface for a specific bus speed, and a host
8 * processor's endianness. This will create and distribute regmaps for any
9 * children.
10 *
11 * Copyright 2021-2022 Innovative Advantage Inc.
12 *
13 * Author: Colin Foster <colin.foster@in-advantage.com>
14 */
15
16#include <linux/device.h>
17#include <linux/err.h>
18#include <linux/errno.h>
19#include <linux/export.h>
20#include <linux/ioport.h>
21#include <linux/mod_devicetable.h>
22#include <linux/module.h>
23#include <linux/regmap.h>
24#include <linux/spi/spi.h>
25#include <linux/types.h>
26#include <linux/units.h>
27
28#include "ocelot.h"
29
30#define REG_DEV_CPUORG_IF_CTRL 0x0000
31#define REG_DEV_CPUORG_IF_CFGSTAT 0x0004
32
33#define CFGSTAT_IF_NUM_VCORE (0 << 24)
34#define CFGSTAT_IF_NUM_VRAP (1 << 24)
35#define CFGSTAT_IF_NUM_SI (2 << 24)
36#define CFGSTAT_IF_NUM_MIIM (3 << 24)
37
38#define VSC7512_DEVCPU_ORG_RES_START 0x71000000
39#define VSC7512_DEVCPU_ORG_RES_SIZE 0x38
40
41#define VSC7512_CHIP_REGS_RES_START 0x71070000
42#define VSC7512_CHIP_REGS_RES_SIZE 0x14
43
44static const struct resource vsc7512_dev_cpuorg_resource =
45 DEFINE_RES_REG_NAMED(VSC7512_DEVCPU_ORG_RES_START,
46 VSC7512_DEVCPU_ORG_RES_SIZE,
47 "devcpu_org");
48
49static const struct resource vsc7512_gcb_resource =
50 DEFINE_RES_REG_NAMED(VSC7512_CHIP_REGS_RES_START,
51 VSC7512_CHIP_REGS_RES_SIZE,
52 "devcpu_gcb_chip_regs");
53
54static int ocelot_spi_initialize(struct device *dev)
55{
56 struct ocelot_ddata *ddata = dev_get_drvdata(dev);
57 u32 val, check;
58 int err;
59
60 val = OCELOT_SPI_BYTE_ORDER;
61
62 /*
63 * The SPI address must be big-endian, but we want the payload to match
64 * our CPU. These are two bits (0 and 1) but they're repeated such that
65 * the write from any configuration will be valid. The four
66 * configurations are:
67 *
68 * 0b00: little-endian, MSB first
69 * | 111111 | 22221111 | 33222222 |
70 * | 76543210 | 54321098 | 32109876 | 10987654 |
71 *
72 * 0b01: big-endian, MSB first
73 * | 33222222 | 22221111 | 111111 | |
74 * | 10987654 | 32109876 | 54321098 | 76543210 |
75 *
76 * 0b10: little-endian, LSB first
77 * | 111111 | 11112222 | 22222233 |
78 * | 01234567 | 89012345 | 67890123 | 45678901 |
79 *
80 * 0b11: big-endian, LSB first
81 * | 22222233 | 11112222 | 111111 | |
82 * | 45678901 | 67890123 | 89012345 | 01234567 |
83 */
84 err = regmap_write(ddata->cpuorg_regmap, REG_DEV_CPUORG_IF_CTRL, val);
85 if (err)
86 return err;
87
88 /*
89 * Apply the number of padding bytes between a read request and the data
90 * payload. Some registers have access times of up to 1us, so if the
91 * first payload bit is shifted out too quickly, the read will fail.
92 */
93 val = ddata->spi_padding_bytes;
94 err = regmap_write(ddata->cpuorg_regmap, REG_DEV_CPUORG_IF_CFGSTAT, val);
95 if (err)
96 return err;
97
98 /*
99 * After we write the interface configuration, read it back here. This
100 * will verify several different things. The first is that the number of
101 * padding bytes actually got written correctly. These are found in bits
102 * 0:3.
103 *
104 * The second is that bit 16 is cleared. Bit 16 is IF_CFGSTAT:IF_STAT,
105 * and will be set if the register access is too fast. This would be in
106 * the condition that the number of padding bytes is insufficient for
107 * the SPI bus frequency.
108 *
109 * The last check is for bits 31:24, which define the interface by which
110 * the registers are being accessed. Since we're accessing them via the
111 * serial interface, it must return IF_NUM_SI.
112 */
113 check = val | CFGSTAT_IF_NUM_SI;
114
115 err = regmap_read(ddata->cpuorg_regmap, REG_DEV_CPUORG_IF_CFGSTAT, &val);
116 if (err)
117 return err;
118
119 if (check != val)
120 return -ENODEV;
121
122 return 0;
123}
124
125static const struct regmap_config ocelot_spi_regmap_config = {
126 .reg_bits = 24,
127 .reg_stride = 4,
128 .reg_downshift = 2,
129 .val_bits = 32,
130
131 .write_flag_mask = 0x80,
132
133 .use_single_write = true,
134 .can_multi_write = false,
135
136 .reg_format_endian = REGMAP_ENDIAN_BIG,
137 .val_format_endian = REGMAP_ENDIAN_NATIVE,
138};
139
140static int ocelot_spi_regmap_bus_read(void *context, const void *reg, size_t reg_size,
141 void *val, size_t val_size)
142{
143 struct spi_transfer xfers[3] = {0};
144 struct device *dev = context;
145 struct ocelot_ddata *ddata;
146 struct spi_device *spi;
147 struct spi_message msg;
148 unsigned int index = 0;
149
150 ddata = dev_get_drvdata(dev);
151 spi = to_spi_device(dev);
152
153 xfers[index].tx_buf = reg;
154 xfers[index].len = reg_size;
155 index++;
156
157 if (ddata->spi_padding_bytes) {
158 xfers[index].len = ddata->spi_padding_bytes;
159 xfers[index].tx_buf = ddata->dummy_buf;
160 xfers[index].dummy_data = 1;
161 index++;
162 }
163
164 xfers[index].rx_buf = val;
165 xfers[index].len = val_size;
166 index++;
167
168 spi_message_init_with_transfers(&msg, xfers, index);
169
170 return spi_sync(spi, &msg);
171}
172
173static int ocelot_spi_regmap_bus_write(void *context, const void *data, size_t count)
174{
175 struct device *dev = context;
176 struct spi_device *spi = to_spi_device(dev);
177
178 return spi_write(spi, data, count);
179}
180
181static const struct regmap_bus ocelot_spi_regmap_bus = {
182 .write = ocelot_spi_regmap_bus_write,
183 .read = ocelot_spi_regmap_bus_read,
184};
185
186struct regmap *ocelot_spi_init_regmap(struct device *dev, const struct resource *res)
187{
188 struct regmap_config regmap_config;
189
190 memcpy(®map_config, &ocelot_spi_regmap_config, sizeof(regmap_config));
191
192 regmap_config.name = res->name;
193 regmap_config.max_register = resource_size(res) - 1;
194 regmap_config.reg_base = res->start;
195
196 return devm_regmap_init(dev, &ocelot_spi_regmap_bus, dev, ®map_config);
197}
198EXPORT_SYMBOL_NS(ocelot_spi_init_regmap, MFD_OCELOT_SPI);
199
200static int ocelot_spi_probe(struct spi_device *spi)
201{
202 struct device *dev = &spi->dev;
203 struct ocelot_ddata *ddata;
204 struct regmap *r;
205 int err;
206
207 ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
208 if (!ddata)
209 return -ENOMEM;
210
211 spi_set_drvdata(spi, ddata);
212
213 if (spi->max_speed_hz <= 500000) {
214 ddata->spi_padding_bytes = 0;
215 } else {
216 /*
217 * Calculation taken from the manual for IF_CFGSTAT:IF_CFG.
218 * Register access time is 1us, so we need to configure and send
219 * out enough padding bytes between the read request and data
220 * transmission that lasts at least 1 microsecond.
221 */
222 ddata->spi_padding_bytes = 1 + (spi->max_speed_hz / HZ_PER_MHZ + 2) / 8;
223
224 ddata->dummy_buf = devm_kzalloc(dev, ddata->spi_padding_bytes, GFP_KERNEL);
225 if (!ddata->dummy_buf)
226 return -ENOMEM;
227 }
228
229 spi->bits_per_word = 8;
230
231 err = spi_setup(spi);
232 if (err)
233 return dev_err_probe(&spi->dev, err, "Error performing SPI setup\n");
234
235 r = ocelot_spi_init_regmap(dev, &vsc7512_dev_cpuorg_resource);
236 if (IS_ERR(r))
237 return PTR_ERR(r);
238
239 ddata->cpuorg_regmap = r;
240
241 r = ocelot_spi_init_regmap(dev, &vsc7512_gcb_resource);
242 if (IS_ERR(r))
243 return PTR_ERR(r);
244
245 ddata->gcb_regmap = r;
246
247 /*
248 * The chip must be set up for SPI before it gets initialized and reset.
249 * This must be done before calling init, and after a chip reset is
250 * performed.
251 */
252 err = ocelot_spi_initialize(dev);
253 if (err)
254 return dev_err_probe(dev, err, "Error initializing SPI bus\n");
255
256 err = ocelot_chip_reset(dev);
257 if (err)
258 return dev_err_probe(dev, err, "Error resetting device\n");
259
260 /*
261 * A chip reset will clear the SPI configuration, so it needs to be done
262 * again before we can access any registers.
263 */
264 err = ocelot_spi_initialize(dev);
265 if (err)
266 return dev_err_probe(dev, err, "Error initializing SPI bus after reset\n");
267
268 err = ocelot_core_init(dev);
269 if (err)
270 return dev_err_probe(dev, err, "Error initializing Ocelot core\n");
271
272 return 0;
273}
274
275static const struct spi_device_id ocelot_spi_ids[] = {
276 { "vsc7512", 0 },
277 { }
278};
279MODULE_DEVICE_TABLE(spi, ocelot_spi_ids);
280
281static const struct of_device_id ocelot_spi_of_match[] = {
282 { .compatible = "mscc,vsc7512" },
283 { }
284};
285MODULE_DEVICE_TABLE(of, ocelot_spi_of_match);
286
287static struct spi_driver ocelot_spi_driver = {
288 .driver = {
289 .name = "ocelot-soc",
290 .of_match_table = ocelot_spi_of_match,
291 },
292 .id_table = ocelot_spi_ids,
293 .probe = ocelot_spi_probe,
294};
295module_spi_driver(ocelot_spi_driver);
296
297MODULE_DESCRIPTION("SPI Controlled Ocelot Chip Driver");
298MODULE_AUTHOR("Colin Foster <colin.foster@in-advantage.com>");
299MODULE_LICENSE("Dual MIT/GPL");
300MODULE_IMPORT_NS(MFD_OCELOT);