1 // SPDX-License-Identifier: GPL-2.0
3 * BCM2835 master mode driver
7 #include <linux/clkdev.h>
8 #include <linux/clk-provider.h>
9 #include <linux/completion.h>
10 #include <linux/err.h>
11 #include <linux/i2c.h>
12 #include <linux/interrupt.h>
14 #include <linux/module.h>
15 #include <linux/of_device.h>
16 #include <linux/platform_device.h>
17 #include <linux/slab.h>
19 #define BCM2835_I2C_C 0x0
20 #define BCM2835_I2C_S 0x4
21 #define BCM2835_I2C_DLEN 0x8
22 #define BCM2835_I2C_A 0xc
23 #define BCM2835_I2C_FIFO 0x10
24 #define BCM2835_I2C_DIV 0x14
25 #define BCM2835_I2C_DEL 0x18
26 #define BCM2835_I2C_CLKT 0x1c
28 #define BCM2835_I2C_C_READ BIT(0)
29 #define BCM2835_I2C_C_CLEAR BIT(4) /* bits 4 and 5 both clear */
30 #define BCM2835_I2C_C_ST BIT(7)
31 #define BCM2835_I2C_C_INTD BIT(8)
32 #define BCM2835_I2C_C_INTT BIT(9)
33 #define BCM2835_I2C_C_INTR BIT(10)
34 #define BCM2835_I2C_C_I2CEN BIT(15)
36 #define BCM2835_I2C_S_TA BIT(0)
37 #define BCM2835_I2C_S_DONE BIT(1)
38 #define BCM2835_I2C_S_TXW BIT(2)
39 #define BCM2835_I2C_S_RXR BIT(3)
40 #define BCM2835_I2C_S_TXD BIT(4)
41 #define BCM2835_I2C_S_RXD BIT(5)
42 #define BCM2835_I2C_S_TXE BIT(6)
43 #define BCM2835_I2C_S_RXF BIT(7)
44 #define BCM2835_I2C_S_ERR BIT(8)
45 #define BCM2835_I2C_S_CLKT BIT(9)
46 #define BCM2835_I2C_S_LEN BIT(10) /* Fake bit for SW error reporting */
48 #define BCM2835_I2C_FEDL_SHIFT 16
49 #define BCM2835_I2C_REDL_SHIFT 0
51 #define BCM2835_I2C_CDIV_MIN 0x0002
52 #define BCM2835_I2C_CDIV_MAX 0xFFFE
54 struct bcm2835_i2c_dev {
58 struct i2c_adapter adapter;
59 struct completion completion;
60 struct i2c_msg *curr_msg;
65 size_t msg_buf_remaining;
68 static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
71 writel(val, i2c_dev->regs + reg);
74 static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
76 return readl(i2c_dev->regs + reg);
79 #define to_clk_bcm2835_i2c(_hw) container_of(_hw, struct clk_bcm2835_i2c, hw)
80 struct clk_bcm2835_i2c {
82 struct bcm2835_i2c_dev *i2c_dev;
85 static int clk_bcm2835_i2c_calc_divider(unsigned long rate,
86 unsigned long parent_rate)
88 u32 divider = DIV_ROUND_UP(parent_rate, rate);
91 * Per the datasheet, the register is always interpreted as an even
92 * number, by rounding down. In other words, the LSB is ignored. So,
93 * if the LSB is set, increment the divider to avoid any issue.
97 if ((divider < BCM2835_I2C_CDIV_MIN) ||
98 (divider > BCM2835_I2C_CDIV_MAX))
104 static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate,
105 unsigned long parent_rate)
107 struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
109 u32 divider = clk_bcm2835_i2c_calc_divider(rate, parent_rate);
111 if (divider == -EINVAL)
114 bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DIV, divider);
117 * Number of core clocks to wait after falling edge before
118 * outputting the next data bit. Note that both FEDL and REDL
119 * can't be greater than CDIV/2.
121 fedl = max(divider / 16, 1u);
124 * Number of core clocks to wait after rising edge before
125 * sampling the next incoming data bit.
127 redl = max(divider / 4, 1u);
129 bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DEL,
130 (fedl << BCM2835_I2C_FEDL_SHIFT) |
131 (redl << BCM2835_I2C_REDL_SHIFT));
135 static long clk_bcm2835_i2c_round_rate(struct clk_hw *hw, unsigned long rate,
136 unsigned long *parent_rate)
138 u32 divider = clk_bcm2835_i2c_calc_divider(rate, *parent_rate);
140 return DIV_ROUND_UP(*parent_rate, divider);
143 static unsigned long clk_bcm2835_i2c_recalc_rate(struct clk_hw *hw,
144 unsigned long parent_rate)
146 struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
147 u32 divider = bcm2835_i2c_readl(div->i2c_dev, BCM2835_I2C_DIV);
149 return DIV_ROUND_UP(parent_rate, divider);
152 static const struct clk_ops clk_bcm2835_i2c_ops = {
153 .set_rate = clk_bcm2835_i2c_set_rate,
154 .round_rate = clk_bcm2835_i2c_round_rate,
155 .recalc_rate = clk_bcm2835_i2c_recalc_rate,
158 static struct clk *bcm2835_i2c_register_div(struct device *dev,
160 struct bcm2835_i2c_dev *i2c_dev)
162 struct clk_init_data init;
163 struct clk_bcm2835_i2c *priv;
165 const char *mclk_name;
167 snprintf(name, sizeof(name), "%s_div", dev_name(dev));
169 mclk_name = __clk_get_name(mclk);
171 init.ops = &clk_bcm2835_i2c_ops;
173 init.parent_names = (const char* []) { mclk_name };
174 init.num_parents = 1;
177 priv = devm_kzalloc(dev, sizeof(struct clk_bcm2835_i2c), GFP_KERNEL);
179 return ERR_PTR(-ENOMEM);
181 priv->hw.init = &init;
182 priv->i2c_dev = i2c_dev;
184 clk_hw_register_clkdev(&priv->hw, "div", dev_name(dev));
185 return devm_clk_register(dev, &priv->hw);
188 static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
192 while (i2c_dev->msg_buf_remaining) {
193 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
194 if (!(val & BCM2835_I2C_S_TXD))
196 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
199 i2c_dev->msg_buf_remaining--;
203 static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
207 while (i2c_dev->msg_buf_remaining) {
208 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
209 if (!(val & BCM2835_I2C_S_RXD))
211 *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
214 i2c_dev->msg_buf_remaining--;
219 * Repeated Start Condition (Sr)
220 * The BCM2835 ARM Peripherals datasheet mentions a way to trigger a Sr when it
221 * talks about reading from a slave with 10 bit address. This is achieved by
222 * issuing a write, poll the I2CS.TA flag and wait for it to be set, and then
224 * A comment in https://github.com/raspberrypi/linux/issues/254 shows how the
225 * firmware actually does it using polling and says that it's a workaround for
226 * a problem in the state machine.
227 * It turns out that it is possible to use the TXW interrupt to know when the
228 * transfer is active, provided the FIFO has not been prefilled.
231 static void bcm2835_i2c_start_transfer(struct bcm2835_i2c_dev *i2c_dev)
233 u32 c = BCM2835_I2C_C_ST | BCM2835_I2C_C_I2CEN;
234 struct i2c_msg *msg = i2c_dev->curr_msg;
235 bool last_msg = (i2c_dev->num_msgs == 1);
237 if (!i2c_dev->num_msgs)
241 i2c_dev->msg_buf = msg->buf;
242 i2c_dev->msg_buf_remaining = msg->len;
244 if (msg->flags & I2C_M_RD)
245 c |= BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
247 c |= BCM2835_I2C_C_INTT;
250 c |= BCM2835_I2C_C_INTD;
252 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
253 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
254 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
257 static void bcm2835_i2c_finish_transfer(struct bcm2835_i2c_dev *i2c_dev)
259 i2c_dev->curr_msg = NULL;
260 i2c_dev->num_msgs = 0;
262 i2c_dev->msg_buf = NULL;
263 i2c_dev->msg_buf_remaining = 0;
267 * Note about I2C_C_CLEAR on error:
268 * The I2C_C_CLEAR on errors will take some time to resolve -- if you were in
269 * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through
270 * the state machine to send a NACK and a STOP. Since we're setting CLEAR
271 * without I2CEN, that NACK will be hanging around queued up for next time
272 * we start the engine.
275 static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
277 struct bcm2835_i2c_dev *i2c_dev = data;
280 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
282 err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
284 i2c_dev->msg_err = err;
288 if (val & BCM2835_I2C_S_DONE) {
289 if (!i2c_dev->curr_msg) {
290 dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n");
291 } else if (i2c_dev->curr_msg->flags & I2C_M_RD) {
292 bcm2835_drain_rxfifo(i2c_dev);
293 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
296 if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining)
297 i2c_dev->msg_err = BCM2835_I2C_S_LEN;
299 i2c_dev->msg_err = 0;
303 if (val & BCM2835_I2C_S_TXW) {
304 if (!i2c_dev->msg_buf_remaining) {
305 i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
309 bcm2835_fill_txfifo(i2c_dev);
311 if (i2c_dev->num_msgs && !i2c_dev->msg_buf_remaining) {
313 bcm2835_i2c_start_transfer(i2c_dev);
319 if (val & BCM2835_I2C_S_RXR) {
320 if (!i2c_dev->msg_buf_remaining) {
321 i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
325 bcm2835_drain_rxfifo(i2c_dev);
332 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
333 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, BCM2835_I2C_S_CLKT |
334 BCM2835_I2C_S_ERR | BCM2835_I2C_S_DONE);
335 complete(&i2c_dev->completion);
340 static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
343 struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
344 unsigned long time_left;
347 for (i = 0; i < (num - 1); i++)
348 if (msgs[i].flags & I2C_M_RD) {
349 dev_warn_once(i2c_dev->dev,
350 "only one read message supported, has to be last\n");
354 i2c_dev->curr_msg = msgs;
355 i2c_dev->num_msgs = num;
356 reinit_completion(&i2c_dev->completion);
358 bcm2835_i2c_start_transfer(i2c_dev);
360 time_left = wait_for_completion_timeout(&i2c_dev->completion,
363 bcm2835_i2c_finish_transfer(i2c_dev);
366 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C,
367 BCM2835_I2C_C_CLEAR);
368 dev_err(i2c_dev->dev, "i2c transfer timed out\n");
372 if (!i2c_dev->msg_err)
375 dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
377 if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
383 static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
385 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
388 static const struct i2c_algorithm bcm2835_i2c_algo = {
389 .master_xfer = bcm2835_i2c_xfer,
390 .functionality = bcm2835_i2c_func,
394 * The BCM2835 was reported to have problems with clock stretching:
395 * https://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
396 * https://www.raspberrypi.org/forums/viewtopic.php?p=146272
398 static const struct i2c_adapter_quirks bcm2835_i2c_quirks = {
399 .flags = I2C_AQ_NO_CLK_STRETCH,
402 static int bcm2835_i2c_probe(struct platform_device *pdev)
404 struct bcm2835_i2c_dev *i2c_dev;
405 struct resource *mem;
407 struct i2c_adapter *adap;
411 i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
414 platform_set_drvdata(pdev, i2c_dev);
415 i2c_dev->dev = &pdev->dev;
416 init_completion(&i2c_dev->completion);
418 mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
419 i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem);
420 if (IS_ERR(i2c_dev->regs))
421 return PTR_ERR(i2c_dev->regs);
423 mclk = devm_clk_get(&pdev->dev, NULL);
425 return dev_err_probe(&pdev->dev, PTR_ERR(mclk),
426 "Could not get clock\n");
428 i2c_dev->bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk, i2c_dev);
430 if (IS_ERR(i2c_dev->bus_clk)) {
431 dev_err(&pdev->dev, "Could not register clock\n");
432 return PTR_ERR(i2c_dev->bus_clk);
435 ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
439 "Could not read clock-frequency property\n");
440 bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ;
443 ret = clk_set_rate_exclusive(i2c_dev->bus_clk, bus_clk_rate);
445 dev_err(&pdev->dev, "Could not set clock frequency\n");
449 ret = clk_prepare_enable(i2c_dev->bus_clk);
451 dev_err(&pdev->dev, "Couldn't prepare clock");
455 i2c_dev->irq = platform_get_irq(pdev, 0);
456 if (i2c_dev->irq < 0)
459 ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
460 dev_name(&pdev->dev), i2c_dev);
462 dev_err(&pdev->dev, "Could not request IRQ\n");
466 adap = &i2c_dev->adapter;
467 i2c_set_adapdata(adap, i2c_dev);
468 adap->owner = THIS_MODULE;
469 adap->class = I2C_CLASS_DEPRECATED;
470 snprintf(adap->name, sizeof(adap->name), "bcm2835 (%s)",
471 of_node_full_name(pdev->dev.of_node));
472 adap->algo = &bcm2835_i2c_algo;
473 adap->dev.parent = &pdev->dev;
474 adap->dev.of_node = pdev->dev.of_node;
475 adap->quirks = of_device_get_match_data(&pdev->dev);
477 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
479 ret = i2c_add_adapter(adap);
481 free_irq(i2c_dev->irq, i2c_dev);
486 static int bcm2835_i2c_remove(struct platform_device *pdev)
488 struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
490 clk_rate_exclusive_put(i2c_dev->bus_clk);
491 clk_disable_unprepare(i2c_dev->bus_clk);
493 free_irq(i2c_dev->irq, i2c_dev);
494 i2c_del_adapter(&i2c_dev->adapter);
499 static const struct of_device_id bcm2835_i2c_of_match[] = {
500 { .compatible = "brcm,bcm2711-i2c" },
501 { .compatible = "brcm,bcm2835-i2c", .data = &bcm2835_i2c_quirks },
504 MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
506 static struct platform_driver bcm2835_i2c_driver = {
507 .probe = bcm2835_i2c_probe,
508 .remove = bcm2835_i2c_remove,
510 .name = "i2c-bcm2835",
511 .of_match_table = bcm2835_i2c_of_match,
514 module_platform_driver(bcm2835_i2c_driver);
516 MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
517 MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
518 MODULE_LICENSE("GPL v2");
519 MODULE_ALIAS("platform:i2c-bcm2835");