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