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Linux/drivers/i2c/busses/i2c-bcm2835.c

  1 /*
  2  * BCM2835 master mode driver
  3  *
  4  * This software is licensed under the terms of the GNU General Public
  5  * License version 2, as published by the Free Software Foundation, and
  6  * may be copied, distributed, and modified under those terms.
  7  *
  8  * This program is distributed in the hope that it will be useful,
  9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 11  * GNU General Public License for more details.
 12  */
 13 
 14 #include <linux/clk.h>
 15 #include <linux/completion.h>
 16 #include <linux/err.h>
 17 #include <linux/i2c.h>
 18 #include <linux/interrupt.h>
 19 #include <linux/io.h>
 20 #include <linux/module.h>
 21 #include <linux/platform_device.h>
 22 #include <linux/slab.h>
 23 
 24 #define BCM2835_I2C_C           0x0
 25 #define BCM2835_I2C_S           0x4
 26 #define BCM2835_I2C_DLEN        0x8
 27 #define BCM2835_I2C_A           0xc
 28 #define BCM2835_I2C_FIFO        0x10
 29 #define BCM2835_I2C_DIV         0x14
 30 #define BCM2835_I2C_DEL         0x18
 31 #define BCM2835_I2C_CLKT        0x1c
 32 
 33 #define BCM2835_I2C_C_READ      BIT(0)
 34 #define BCM2835_I2C_C_CLEAR     BIT(4) /* bits 4 and 5 both clear */
 35 #define BCM2835_I2C_C_ST        BIT(7)
 36 #define BCM2835_I2C_C_INTD      BIT(8)
 37 #define BCM2835_I2C_C_INTT      BIT(9)
 38 #define BCM2835_I2C_C_INTR      BIT(10)
 39 #define BCM2835_I2C_C_I2CEN     BIT(15)
 40 
 41 #define BCM2835_I2C_S_TA        BIT(0)
 42 #define BCM2835_I2C_S_DONE      BIT(1)
 43 #define BCM2835_I2C_S_TXW       BIT(2)
 44 #define BCM2835_I2C_S_RXR       BIT(3)
 45 #define BCM2835_I2C_S_TXD       BIT(4)
 46 #define BCM2835_I2C_S_RXD       BIT(5)
 47 #define BCM2835_I2C_S_TXE       BIT(6)
 48 #define BCM2835_I2C_S_RXF       BIT(7)
 49 #define BCM2835_I2C_S_ERR       BIT(8)
 50 #define BCM2835_I2C_S_CLKT      BIT(9)
 51 #define BCM2835_I2C_S_LEN       BIT(10) /* Fake bit for SW error reporting */
 52 
 53 #define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000))
 54 
 55 struct bcm2835_i2c_dev {
 56         struct device *dev;
 57         void __iomem *regs;
 58         struct clk *clk;
 59         int irq;
 60         struct i2c_adapter adapter;
 61         struct completion completion;
 62         u32 msg_err;
 63         u8 *msg_buf;
 64         size_t msg_buf_remaining;
 65 };
 66 
 67 static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
 68                                       u32 reg, u32 val)
 69 {
 70         writel(val, i2c_dev->regs + reg);
 71 }
 72 
 73 static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
 74 {
 75         return readl(i2c_dev->regs + reg);
 76 }
 77 
 78 static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
 79 {
 80         u32 val;
 81 
 82         while (i2c_dev->msg_buf_remaining) {
 83                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 84                 if (!(val & BCM2835_I2C_S_TXD))
 85                         break;
 86                 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
 87                                    *i2c_dev->msg_buf);
 88                 i2c_dev->msg_buf++;
 89                 i2c_dev->msg_buf_remaining--;
 90         }
 91 }
 92 
 93 static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
 94 {
 95         u32 val;
 96 
 97         while (i2c_dev->msg_buf_remaining) {
 98                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 99                 if (!(val & BCM2835_I2C_S_RXD))
100                         break;
101                 *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
102                                                       BCM2835_I2C_FIFO);
103                 i2c_dev->msg_buf++;
104                 i2c_dev->msg_buf_remaining--;
105         }
106 }
107 
108 static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
109 {
110         struct bcm2835_i2c_dev *i2c_dev = data;
111         u32 val, err;
112 
113         val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
114         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val);
115 
116         err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
117         if (err) {
118                 i2c_dev->msg_err = err;
119                 complete(&i2c_dev->completion);
120                 return IRQ_HANDLED;
121         }
122 
123         if (val & BCM2835_I2C_S_RXD) {
124                 bcm2835_drain_rxfifo(i2c_dev);
125                 if (!(val & BCM2835_I2C_S_DONE))
126                         return IRQ_HANDLED;
127         }
128 
129         if (val & BCM2835_I2C_S_DONE) {
130                 if (i2c_dev->msg_buf_remaining)
131                         i2c_dev->msg_err = BCM2835_I2C_S_LEN;
132                 else
133                         i2c_dev->msg_err = 0;
134                 complete(&i2c_dev->completion);
135                 return IRQ_HANDLED;
136         }
137 
138         if (val & BCM2835_I2C_S_TXD) {
139                 bcm2835_fill_txfifo(i2c_dev);
140                 return IRQ_HANDLED;
141         }
142 
143         return IRQ_NONE;
144 }
145 
146 static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
147                                 struct i2c_msg *msg)
148 {
149         u32 c;
150         int time_left;
151 
152         i2c_dev->msg_buf = msg->buf;
153         i2c_dev->msg_buf_remaining = msg->len;
154         reinit_completion(&i2c_dev->completion);
155 
156         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
157 
158         if (msg->flags & I2C_M_RD) {
159                 c = BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
160         } else {
161                 c = BCM2835_I2C_C_INTT;
162                 bcm2835_fill_txfifo(i2c_dev);
163         }
164         c |= BCM2835_I2C_C_ST | BCM2835_I2C_C_INTD | BCM2835_I2C_C_I2CEN;
165 
166         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
167         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
168         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
169 
170         time_left = wait_for_completion_timeout(&i2c_dev->completion,
171                                                 BCM2835_I2C_TIMEOUT);
172         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
173         if (!time_left) {
174                 dev_err(i2c_dev->dev, "i2c transfer timed out\n");
175                 return -ETIMEDOUT;
176         }
177 
178         if (likely(!i2c_dev->msg_err))
179                 return 0;
180 
181         if ((i2c_dev->msg_err & BCM2835_I2C_S_ERR) &&
182             (msg->flags & I2C_M_IGNORE_NAK))
183                 return 0;
184 
185         dev_err(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
186 
187         if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
188                 return -EREMOTEIO;
189         else
190                 return -EIO;
191 }
192 
193 static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
194                             int num)
195 {
196         struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
197         int i;
198         int ret = 0;
199 
200         for (i = 0; i < num; i++) {
201                 ret = bcm2835_i2c_xfer_msg(i2c_dev, &msgs[i]);
202                 if (ret)
203                         break;
204         }
205 
206         return ret ?: i;
207 }
208 
209 static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
210 {
211         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
212 }
213 
214 static const struct i2c_algorithm bcm2835_i2c_algo = {
215         .master_xfer    = bcm2835_i2c_xfer,
216         .functionality  = bcm2835_i2c_func,
217 };
218 
219 static int bcm2835_i2c_probe(struct platform_device *pdev)
220 {
221         struct bcm2835_i2c_dev *i2c_dev;
222         struct resource *mem, *irq;
223         u32 bus_clk_rate, divider;
224         int ret;
225         struct i2c_adapter *adap;
226 
227         i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
228         if (!i2c_dev)
229                 return -ENOMEM;
230         platform_set_drvdata(pdev, i2c_dev);
231         i2c_dev->dev = &pdev->dev;
232         init_completion(&i2c_dev->completion);
233 
234         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
235         i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem);
236         if (IS_ERR(i2c_dev->regs))
237                 return PTR_ERR(i2c_dev->regs);
238 
239         i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
240         if (IS_ERR(i2c_dev->clk)) {
241                 dev_err(&pdev->dev, "Could not get clock\n");
242                 return PTR_ERR(i2c_dev->clk);
243         }
244 
245         ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
246                                    &bus_clk_rate);
247         if (ret < 0) {
248                 dev_warn(&pdev->dev,
249                          "Could not read clock-frequency property\n");
250                 bus_clk_rate = 100000;
251         }
252 
253         divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), bus_clk_rate);
254         /*
255          * Per the datasheet, the register is always interpreted as an even
256          * number, by rounding down. In other words, the LSB is ignored. So,
257          * if the LSB is set, increment the divider to avoid any issue.
258          */
259         if (divider & 1)
260                 divider++;
261         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
262 
263         irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
264         if (!irq) {
265                 dev_err(&pdev->dev, "No IRQ resource\n");
266                 return -ENODEV;
267         }
268         i2c_dev->irq = irq->start;
269 
270         ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
271                           dev_name(&pdev->dev), i2c_dev);
272         if (ret) {
273                 dev_err(&pdev->dev, "Could not request IRQ\n");
274                 return -ENODEV;
275         }
276 
277         adap = &i2c_dev->adapter;
278         i2c_set_adapdata(adap, i2c_dev);
279         adap->owner = THIS_MODULE;
280         adap->class = I2C_CLASS_HWMON | I2C_CLASS_DEPRECATED;
281         strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name));
282         adap->algo = &bcm2835_i2c_algo;
283         adap->dev.parent = &pdev->dev;
284         adap->dev.of_node = pdev->dev.of_node;
285 
286         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
287 
288         ret = i2c_add_adapter(adap);
289         if (ret)
290                 free_irq(i2c_dev->irq, i2c_dev);
291 
292         return ret;
293 }
294 
295 static int bcm2835_i2c_remove(struct platform_device *pdev)
296 {
297         struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
298 
299         free_irq(i2c_dev->irq, i2c_dev);
300         i2c_del_adapter(&i2c_dev->adapter);
301 
302         return 0;
303 }
304 
305 static const struct of_device_id bcm2835_i2c_of_match[] = {
306         { .compatible = "brcm,bcm2835-i2c" },
307         {},
308 };
309 MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
310 
311 static struct platform_driver bcm2835_i2c_driver = {
312         .probe          = bcm2835_i2c_probe,
313         .remove         = bcm2835_i2c_remove,
314         .driver         = {
315                 .name   = "i2c-bcm2835",
316                 .owner  = THIS_MODULE,
317                 .of_match_table = bcm2835_i2c_of_match,
318         },
319 };
320 module_platform_driver(bcm2835_i2c_driver);
321 
322 MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
323 MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
324 MODULE_LICENSE("GPL v2");
325 MODULE_ALIAS("platform:i2c-bcm2835");
326 

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