1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright Intel Corporation (C) 2017.
4 *
5 * Based on the i2c-axxia.c driver.
6 */
7 #include <linux/clk.h>
8 #include <linux/clkdev.h>
9 #include <linux/err.h>
10 #include <linux/i2c.h>
11 #include <linux/iopoll.h>
12 #include <linux/interrupt.h>
13 #include <linux/module.h>
14 #include <linux/io.h>
15 #include <linux/kernel.h>
16 #include <linux/platform_device.h>
17
18 #define ALTR_I2C_TFR_CMD 0x00 /* Transfer Command register */
19 #define ALTR_I2C_TFR_CMD_STA BIT(9) /* send START before byte */
20 #define ALTR_I2C_TFR_CMD_STO BIT(8) /* send STOP after byte */
21 #define ALTR_I2C_TFR_CMD_RW_D BIT(0) /* Direction of transfer */
22 #define ALTR_I2C_RX_DATA 0x04 /* RX data FIFO register */
23 #define ALTR_I2C_CTRL 0x08 /* Control register */
24 #define ALTR_I2C_CTRL_RXT_SHFT 4 /* RX FIFO Threshold */
25 #define ALTR_I2C_CTRL_TCT_SHFT 2 /* TFER CMD FIFO Threshold */
26 #define ALTR_I2C_CTRL_BSPEED BIT(1) /* Bus Speed (1=Fast) */
27 #define ALTR_I2C_CTRL_EN BIT(0) /* Enable Core (1=Enable) */
28 #define ALTR_I2C_ISER 0x0C /* Interrupt Status Enable register */
29 #define ALTR_I2C_ISER_RXOF_EN BIT(4) /* Enable RX OVERFLOW IRQ */
30 #define ALTR_I2C_ISER_ARB_EN BIT(3) /* Enable ARB LOST IRQ */
31 #define ALTR_I2C_ISER_NACK_EN BIT(2) /* Enable NACK DET IRQ */
32 #define ALTR_I2C_ISER_RXRDY_EN BIT(1) /* Enable RX Ready IRQ */
33 #define ALTR_I2C_ISER_TXRDY_EN BIT(0) /* Enable TX Ready IRQ */
34 #define ALTR_I2C_ISR 0x10 /* Interrupt Status register */
35 #define ALTR_I2C_ISR_RXOF BIT(4) /* RX OVERFLOW IRQ */
36 #define ALTR_I2C_ISR_ARB BIT(3) /* ARB LOST IRQ */
37 #define ALTR_I2C_ISR_NACK BIT(2) /* NACK DET IRQ */
38 #define ALTR_I2C_ISR_RXRDY BIT(1) /* RX Ready IRQ */
39 #define ALTR_I2C_ISR_TXRDY BIT(0) /* TX Ready IRQ */
40 #define ALTR_I2C_STATUS 0x14 /* Status register */
41 #define ALTR_I2C_STAT_CORE BIT(0) /* Core Status (0=idle) */
42 #define ALTR_I2C_TC_FIFO_LVL 0x18 /* Transfer FIFO LVL register */
43 #define ALTR_I2C_RX_FIFO_LVL 0x1C /* Receive FIFO LVL register */
44 #define ALTR_I2C_SCL_LOW 0x20 /* SCL low count register */
45 #define ALTR_I2C_SCL_HIGH 0x24 /* SCL high count register */
46 #define ALTR_I2C_SDA_HOLD 0x28 /* SDA hold count register */
47
48 #define ALTR_I2C_ALL_IRQ (ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | \
49 ALTR_I2C_ISR_NACK | ALTR_I2C_ISR_RXRDY | \
50 ALTR_I2C_ISR_TXRDY)
51
52 #define ALTR_I2C_THRESHOLD 0 /* IRQ Threshold at 1 element */
53 #define ALTR_I2C_DFLT_FIFO_SZ 4
54 #define ALTR_I2C_TIMEOUT 100000 /* 100ms */
55 #define ALTR_I2C_XFER_TIMEOUT (msecs_to_jiffies(250))
56
57 /**
58 * struct altr_i2c_dev - I2C device context
59 * @base: pointer to register struct
60 * @msg: pointer to current message
61 * @msg_len: number of bytes transferred in msg
62 * @msg_err: error code for completed message
63 * @msg_complete: xfer completion object
64 * @dev: device reference
65 * @adapter: core i2c abstraction
66 * @i2c_clk: clock reference for i2c input clock
67 * @bus_clk_rate: current i2c bus clock rate
68 * @buf: ptr to msg buffer for easier use.
69 * @fifo_size: size of the FIFO passed in.
70 * @isr_mask: cached copy of local ISR enables.
71 * @isr_status: cached copy of local ISR status.
72 * @isr_mutex: mutex for IRQ thread.
73 */
74 struct altr_i2c_dev {
75 void __iomem *base;
76 struct i2c_msg *msg;
77 size_t msg_len;
78 int msg_err;
79 struct completion msg_complete;
80 struct device *dev;
81 struct i2c_adapter adapter;
82 struct clk *i2c_clk;
83 u32 bus_clk_rate;
84 u8 *buf;
85 u32 fifo_size;
86 u32 isr_mask;
87 u32 isr_status;
88 struct mutex isr_mutex;
89 };
90
91 static void
altr_i2c_int_enable(struct altr_i2c_dev * idev,u32 mask,bool enable)92 altr_i2c_int_enable(struct altr_i2c_dev *idev, u32 mask, bool enable)
93 {
94 u32 int_en;
95
96 int_en = readl(idev->base + ALTR_I2C_ISER);
97 if (enable)
98 idev->isr_mask = int_en | mask;
99 else
100 idev->isr_mask = int_en & ~mask;
101
102 writel(idev->isr_mask, idev->base + ALTR_I2C_ISER);
103 }
104
altr_i2c_int_clear(struct altr_i2c_dev * idev,u32 mask)105 static void altr_i2c_int_clear(struct altr_i2c_dev *idev, u32 mask)
106 {
107 u32 int_en = readl(idev->base + ALTR_I2C_ISR);
108
109 writel(int_en | mask, idev->base + ALTR_I2C_ISR);
110 }
111
altr_i2c_core_disable(struct altr_i2c_dev * idev)112 static void altr_i2c_core_disable(struct altr_i2c_dev *idev)
113 {
114 u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
115
116 writel(tmp & ~ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
117 }
118
altr_i2c_core_enable(struct altr_i2c_dev * idev)119 static void altr_i2c_core_enable(struct altr_i2c_dev *idev)
120 {
121 u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
122
123 writel(tmp | ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
124 }
125
altr_i2c_reset(struct altr_i2c_dev * idev)126 static void altr_i2c_reset(struct altr_i2c_dev *idev)
127 {
128 altr_i2c_core_disable(idev);
129 altr_i2c_core_enable(idev);
130 }
131
altr_i2c_stop(struct altr_i2c_dev * idev)132 static inline void altr_i2c_stop(struct altr_i2c_dev *idev)
133 {
134 writel(ALTR_I2C_TFR_CMD_STO, idev->base + ALTR_I2C_TFR_CMD);
135 }
136
altr_i2c_init(struct altr_i2c_dev * idev)137 static void altr_i2c_init(struct altr_i2c_dev *idev)
138 {
139 u32 divisor = clk_get_rate(idev->i2c_clk) / idev->bus_clk_rate;
140 u32 clk_mhz = clk_get_rate(idev->i2c_clk) / 1000000;
141 u32 tmp = (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_RXT_SHFT) |
142 (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_TCT_SHFT);
143 u32 t_high, t_low;
144
145 if (idev->bus_clk_rate <= I2C_MAX_STANDARD_MODE_FREQ) {
146 tmp &= ~ALTR_I2C_CTRL_BSPEED;
147 /* Standard mode SCL 50/50 */
148 t_high = divisor * 1 / 2;
149 t_low = divisor * 1 / 2;
150 } else {
151 tmp |= ALTR_I2C_CTRL_BSPEED;
152 /* Fast mode SCL 33/66 */
153 t_high = divisor * 1 / 3;
154 t_low = divisor * 2 / 3;
155 }
156 writel(tmp, idev->base + ALTR_I2C_CTRL);
157
158 dev_dbg(idev->dev, "rate=%uHz per_clk=%uMHz -> ratio=1:%u\n",
159 idev->bus_clk_rate, clk_mhz, divisor);
160
161 /* Reset controller */
162 altr_i2c_reset(idev);
163
164 /* SCL High Time */
165 writel(t_high, idev->base + ALTR_I2C_SCL_HIGH);
166 /* SCL Low Time */
167 writel(t_low, idev->base + ALTR_I2C_SCL_LOW);
168 /* SDA Hold Time, 300ns */
169 writel(3 * clk_mhz / 10, idev->base + ALTR_I2C_SDA_HOLD);
170
171 /* Mask all master interrupt bits */
172 altr_i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
173 }
174
175 /*
176 * altr_i2c_transfer - On the last byte to be transmitted, send
177 * a Stop bit on the last byte.
178 */
altr_i2c_transfer(struct altr_i2c_dev * idev,u32 data)179 static void altr_i2c_transfer(struct altr_i2c_dev *idev, u32 data)
180 {
181 /* On the last byte to be transmitted, send STOP */
182 if (idev->msg_len == 1)
183 data |= ALTR_I2C_TFR_CMD_STO;
184 if (idev->msg_len > 0)
185 writel(data, idev->base + ALTR_I2C_TFR_CMD);
186 }
187
188 /*
189 * altr_i2c_empty_rx_fifo - Fetch data from RX FIFO until end of
190 * transfer. Send a Stop bit on the last byte.
191 */
altr_i2c_empty_rx_fifo(struct altr_i2c_dev * idev)192 static void altr_i2c_empty_rx_fifo(struct altr_i2c_dev *idev)
193 {
194 size_t rx_fifo_avail = readl(idev->base + ALTR_I2C_RX_FIFO_LVL);
195 int bytes_to_transfer = min(rx_fifo_avail, idev->msg_len);
196
197 while (bytes_to_transfer-- > 0) {
198 *idev->buf++ = readl(idev->base + ALTR_I2C_RX_DATA);
199 idev->msg_len--;
200 altr_i2c_transfer(idev, 0);
201 }
202 }
203
204 /*
205 * altr_i2c_fill_tx_fifo - Fill TX FIFO from current message buffer.
206 */
altr_i2c_fill_tx_fifo(struct altr_i2c_dev * idev)207 static int altr_i2c_fill_tx_fifo(struct altr_i2c_dev *idev)
208 {
209 size_t tx_fifo_avail = idev->fifo_size - readl(idev->base +
210 ALTR_I2C_TC_FIFO_LVL);
211 int bytes_to_transfer = min(tx_fifo_avail, idev->msg_len);
212 int ret = idev->msg_len - bytes_to_transfer;
213
214 while (bytes_to_transfer-- > 0) {
215 altr_i2c_transfer(idev, *idev->buf++);
216 idev->msg_len--;
217 }
218
219 return ret;
220 }
221
altr_i2c_isr_quick(int irq,void * _dev)222 static irqreturn_t altr_i2c_isr_quick(int irq, void *_dev)
223 {
224 struct altr_i2c_dev *idev = _dev;
225 irqreturn_t ret = IRQ_HANDLED;
226
227 /* Read IRQ status but only interested in Enabled IRQs. */
228 idev->isr_status = readl(idev->base + ALTR_I2C_ISR) & idev->isr_mask;
229 if (idev->isr_status)
230 ret = IRQ_WAKE_THREAD;
231
232 return ret;
233 }
234
altr_i2c_isr(int irq,void * _dev)235 static irqreturn_t altr_i2c_isr(int irq, void *_dev)
236 {
237 int ret;
238 bool read, finish = false;
239 struct altr_i2c_dev *idev = _dev;
240 u32 status = idev->isr_status;
241
242 mutex_lock(&idev->isr_mutex);
243 if (!idev->msg) {
244 dev_warn(idev->dev, "unexpected interrupt\n");
245 altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
246 goto out;
247 }
248 read = (idev->msg->flags & I2C_M_RD) != 0;
249
250 /* handle Lost Arbitration */
251 if (unlikely(status & ALTR_I2C_ISR_ARB)) {
252 altr_i2c_int_clear(idev, ALTR_I2C_ISR_ARB);
253 idev->msg_err = -EAGAIN;
254 finish = true;
255 } else if (unlikely(status & ALTR_I2C_ISR_NACK)) {
256 dev_dbg(idev->dev, "Could not get ACK\n");
257 idev->msg_err = -ENXIO;
258 altr_i2c_int_clear(idev, ALTR_I2C_ISR_NACK);
259 altr_i2c_stop(idev);
260 finish = true;
261 } else if (read && unlikely(status & ALTR_I2C_ISR_RXOF)) {
262 /* handle RX FIFO Overflow */
263 altr_i2c_empty_rx_fifo(idev);
264 altr_i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
265 altr_i2c_stop(idev);
266 dev_err(idev->dev, "RX FIFO Overflow\n");
267 finish = true;
268 } else if (read && (status & ALTR_I2C_ISR_RXRDY)) {
269 /* RX FIFO needs service? */
270 altr_i2c_empty_rx_fifo(idev);
271 altr_i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
272 if (!idev->msg_len)
273 finish = true;
274 } else if (!read && (status & ALTR_I2C_ISR_TXRDY)) {
275 /* TX FIFO needs service? */
276 altr_i2c_int_clear(idev, ALTR_I2C_ISR_TXRDY);
277 if (idev->msg_len > 0)
278 altr_i2c_fill_tx_fifo(idev);
279 else
280 finish = true;
281 } else {
282 dev_warn(idev->dev, "Unexpected interrupt: 0x%x\n", status);
283 altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
284 }
285
286 if (finish) {
287 /* Wait for the Core to finish */
288 ret = readl_poll_timeout_atomic(idev->base + ALTR_I2C_STATUS,
289 status,
290 !(status & ALTR_I2C_STAT_CORE),
291 1, ALTR_I2C_TIMEOUT);
292 if (ret)
293 dev_err(idev->dev, "message timeout\n");
294 altr_i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
295 altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
296 complete(&idev->msg_complete);
297 dev_dbg(idev->dev, "Message Complete\n");
298 }
299 out:
300 mutex_unlock(&idev->isr_mutex);
301
302 return IRQ_HANDLED;
303 }
304
altr_i2c_xfer_msg(struct altr_i2c_dev * idev,struct i2c_msg * msg)305 static int altr_i2c_xfer_msg(struct altr_i2c_dev *idev, struct i2c_msg *msg)
306 {
307 u32 imask = ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | ALTR_I2C_ISR_NACK;
308 unsigned long time_left;
309 u32 value;
310 u8 addr = i2c_8bit_addr_from_msg(msg);
311
312 mutex_lock(&idev->isr_mutex);
313 idev->msg = msg;
314 idev->msg_len = msg->len;
315 idev->buf = msg->buf;
316 idev->msg_err = 0;
317 reinit_completion(&idev->msg_complete);
318 altr_i2c_core_enable(idev);
319
320 /* Make sure RX FIFO is empty */
321 do {
322 readl(idev->base + ALTR_I2C_RX_DATA);
323 } while (readl(idev->base + ALTR_I2C_RX_FIFO_LVL));
324
325 writel(ALTR_I2C_TFR_CMD_STA | addr, idev->base + ALTR_I2C_TFR_CMD);
326
327 if ((msg->flags & I2C_M_RD) != 0) {
328 imask |= ALTR_I2C_ISER_RXOF_EN | ALTR_I2C_ISER_RXRDY_EN;
329 altr_i2c_int_enable(idev, imask, true);
330 /* write the first byte to start the RX */
331 altr_i2c_transfer(idev, 0);
332 } else {
333 imask |= ALTR_I2C_ISR_TXRDY;
334 altr_i2c_int_enable(idev, imask, true);
335 altr_i2c_fill_tx_fifo(idev);
336 }
337 mutex_unlock(&idev->isr_mutex);
338
339 time_left = wait_for_completion_timeout(&idev->msg_complete,
340 ALTR_I2C_XFER_TIMEOUT);
341 mutex_lock(&idev->isr_mutex);
342 altr_i2c_int_enable(idev, imask, false);
343
344 value = readl(idev->base + ALTR_I2C_STATUS) & ALTR_I2C_STAT_CORE;
345 if (value)
346 dev_err(idev->dev, "Core Status not IDLE...\n");
347
348 if (time_left == 0) {
349 idev->msg_err = -ETIMEDOUT;
350 dev_dbg(idev->dev, "Transaction timed out.\n");
351 }
352
353 altr_i2c_core_disable(idev);
354 mutex_unlock(&idev->isr_mutex);
355
356 return idev->msg_err;
357 }
358
359 static int
altr_i2c_xfer(struct i2c_adapter * adap,struct i2c_msg * msgs,int num)360 altr_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
361 {
362 struct altr_i2c_dev *idev = i2c_get_adapdata(adap);
363 int i, ret;
364
365 for (i = 0; i < num; i++) {
366 ret = altr_i2c_xfer_msg(idev, msgs++);
367 if (ret)
368 return ret;
369 }
370 return num;
371 }
372
altr_i2c_func(struct i2c_adapter * adap)373 static u32 altr_i2c_func(struct i2c_adapter *adap)
374 {
375 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
376 }
377
378 static const struct i2c_algorithm altr_i2c_algo = {
379 .master_xfer = altr_i2c_xfer,
380 .functionality = altr_i2c_func,
381 };
382
altr_i2c_probe(struct platform_device * pdev)383 static int altr_i2c_probe(struct platform_device *pdev)
384 {
385 struct altr_i2c_dev *idev = NULL;
386 int irq, ret;
387
388 idev = devm_kzalloc(&pdev->dev, sizeof(*idev), GFP_KERNEL);
389 if (!idev)
390 return -ENOMEM;
391
392 idev->base = devm_platform_ioremap_resource(pdev, 0);
393 if (IS_ERR(idev->base))
394 return PTR_ERR(idev->base);
395
396 irq = platform_get_irq(pdev, 0);
397 if (irq < 0)
398 return irq;
399
400 idev->i2c_clk = devm_clk_get(&pdev->dev, NULL);
401 if (IS_ERR(idev->i2c_clk)) {
402 dev_err(&pdev->dev, "missing clock\n");
403 return PTR_ERR(idev->i2c_clk);
404 }
405
406 idev->dev = &pdev->dev;
407 init_completion(&idev->msg_complete);
408 mutex_init(&idev->isr_mutex);
409
410 ret = device_property_read_u32(idev->dev, "fifo-size",
411 &idev->fifo_size);
412 if (ret) {
413 dev_err(&pdev->dev, "FIFO size set to default of %d\n",
414 ALTR_I2C_DFLT_FIFO_SZ);
415 idev->fifo_size = ALTR_I2C_DFLT_FIFO_SZ;
416 }
417
418 ret = device_property_read_u32(idev->dev, "clock-frequency",
419 &idev->bus_clk_rate);
420 if (ret) {
421 dev_err(&pdev->dev, "Default to 100kHz\n");
422 idev->bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ; /* default clock rate */
423 }
424
425 if (idev->bus_clk_rate > I2C_MAX_FAST_MODE_FREQ) {
426 dev_err(&pdev->dev, "invalid clock-frequency %d\n",
427 idev->bus_clk_rate);
428 return -EINVAL;
429 }
430
431 ret = devm_request_threaded_irq(&pdev->dev, irq, altr_i2c_isr_quick,
432 altr_i2c_isr, IRQF_ONESHOT,
433 pdev->name, idev);
434 if (ret) {
435 dev_err(&pdev->dev, "failed to claim IRQ %d\n", irq);
436 return ret;
437 }
438
439 ret = clk_prepare_enable(idev->i2c_clk);
440 if (ret) {
441 dev_err(&pdev->dev, "failed to enable clock\n");
442 return ret;
443 }
444
445 mutex_lock(&idev->isr_mutex);
446 altr_i2c_init(idev);
447 mutex_unlock(&idev->isr_mutex);
448
449 i2c_set_adapdata(&idev->adapter, idev);
450 strscpy(idev->adapter.name, pdev->name, sizeof(idev->adapter.name));
451 idev->adapter.owner = THIS_MODULE;
452 idev->adapter.algo = &altr_i2c_algo;
453 idev->adapter.dev.parent = &pdev->dev;
454 idev->adapter.dev.of_node = pdev->dev.of_node;
455
456 platform_set_drvdata(pdev, idev);
457
458 ret = i2c_add_adapter(&idev->adapter);
459 if (ret) {
460 clk_disable_unprepare(idev->i2c_clk);
461 return ret;
462 }
463 dev_info(&pdev->dev, "Altera SoftIP I2C Probe Complete\n");
464
465 return 0;
466 }
467
altr_i2c_remove(struct platform_device * pdev)468 static void altr_i2c_remove(struct platform_device *pdev)
469 {
470 struct altr_i2c_dev *idev = platform_get_drvdata(pdev);
471
472 clk_disable_unprepare(idev->i2c_clk);
473 i2c_del_adapter(&idev->adapter);
474 }
475
476 /* Match table for of_platform binding */
477 static const struct of_device_id altr_i2c_of_match[] = {
478 { .compatible = "altr,softip-i2c-v1.0" },
479 {},
480 };
481 MODULE_DEVICE_TABLE(of, altr_i2c_of_match);
482
483 static struct platform_driver altr_i2c_driver = {
484 .probe = altr_i2c_probe,
485 .remove_new = altr_i2c_remove,
486 .driver = {
487 .name = "altera-i2c",
488 .of_match_table = altr_i2c_of_match,
489 },
490 };
491
492 module_platform_driver(altr_i2c_driver);
493
494 MODULE_DESCRIPTION("Altera Soft IP I2C bus driver");
495 MODULE_AUTHOR("Thor Thayer <thor.thayer@linux.intel.com>");
496 MODULE_LICENSE("GPL v2");
497
