drivers/i2c/busses/i2c-sun6i-p2wi.c

   1 /*
   2  * P2WI (Push-Pull Two Wire Interface) bus driver.
   3  *
   4  * Author: Boris BREZILLON <boris.brezillon@free-electrons.com>
   5  *
   6  * This file is licensed under the terms of the GNU General Public License
   7  * version 2.  This program is licensed "as is" without any warranty of any
   8  * kind, whether express or implied.
   9  *
  10  * The P2WI controller looks like an SMBus controller which only supports byte
  11  * data transfers. But, it differs from standard SMBus protocol on several
  12  * aspects:
  13  * - it supports only one slave device, and thus drop the address field
  14  * - it adds a parity bit every 8bits of data
  15  * - only one read access is required to read a byte (instead of a write
  16  *   followed by a read access in standard SMBus protocol)
  17  * - there's no Ack bit after each byte transfer
  18  *
  19  * This means this bus cannot be used to interface with standard SMBus
  20  * devices (the only known device to support this interface is the AXP221
  21  * PMIC).
  22  *
  23  */
  24 #include <linux/clk.h>
  25 #include <linux/i2c.h>
  26 #include <linux/io.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/module.h>
  29 #include <linux/of.h>
  30 #include <linux/platform_device.h>
  31 #include <linux/reset.h>
  32
  33
  34 /* P2WI registers */
  35 #define P2WI_CTRL               0x0
  36 #define P2WI_CCR                0x4
  37 #define P2WI_INTE               0x8
  38 #define P2WI_INTS               0xc
  39 #define P2WI_DADDR0             0x10
  40 #define P2WI_DADDR1             0x14
  41 #define P2WI_DLEN               0x18
  42 #define P2WI_DATA0              0x1c
  43 #define P2WI_DATA1              0x20
  44 #define P2WI_LCR                0x24
  45 #define P2WI_PMCR               0x28
  46
  47 /* CTRL fields */
  48 #define P2WI_CTRL_START_TRANS           BIT(7)
  49 #define P2WI_CTRL_ABORT_TRANS           BIT(6)
  50 #define P2WI_CTRL_GLOBAL_INT_ENB        BIT(1)
  51 #define P2WI_CTRL_SOFT_RST              BIT(0)
  52
  53 /* CLK CTRL fields */
  54 #define P2WI_CCR_SDA_OUT_DELAY(v)       (((v) & 0x7) << 8)
  55 #define P2WI_CCR_MAX_CLK_DIV            0xff
  56 #define P2WI_CCR_CLK_DIV(v)             ((v) & P2WI_CCR_MAX_CLK_DIV)
  57
  58 /* STATUS fields */
  59 #define P2WI_INTS_TRANS_ERR_ID(v)       (((v) >> 8) & 0xff)
  60 #define P2WI_INTS_LOAD_BSY              BIT(2)
  61 #define P2WI_INTS_TRANS_ERR             BIT(1)
  62 #define P2WI_INTS_TRANS_OVER            BIT(0)
  63
  64 /* DATA LENGTH fields*/
  65 #define P2WI_DLEN_READ                  BIT(4)
  66 #define P2WI_DLEN_DATA_LENGTH(v)        ((v - 1) & 0x7)
  67
  68 /* LINE CTRL fields*/
  69 #define P2WI_LCR_SCL_STATE              BIT(5)
  70 #define P2WI_LCR_SDA_STATE              BIT(4)
  71 #define P2WI_LCR_SCL_CTL                BIT(3)
  72 #define P2WI_LCR_SCL_CTL_EN             BIT(2)
  73 #define P2WI_LCR_SDA_CTL                BIT(1)
  74 #define P2WI_LCR_SDA_CTL_EN             BIT(0)
  75
  76 /* PMU MODE CTRL fields */
  77 #define P2WI_PMCR_PMU_INIT_SEND         BIT(31)
  78 #define P2WI_PMCR_PMU_INIT_DATA(v)      (((v) & 0xff) << 16)
  79 #define P2WI_PMCR_PMU_MODE_REG(v)       (((v) & 0xff) << 8)
  80 #define P2WI_PMCR_PMU_DEV_ADDR(v)       ((v) & 0xff)
  81
  82 #define P2WI_MAX_FREQ                   6000000
  83
  84 struct p2wi {
  85         struct i2c_adapter adapter;
  86         struct completion complete;
  87         unsigned int status;
  88         void __iomem *regs;
  89         struct clk *clk;
  90         struct reset_control *rstc;
  91         int slave_addr;
  92 };
  93
  94 static irqreturn_t p2wi_interrupt(int irq, void *dev_id)
  95 {
  96         struct p2wi *p2wi = dev_id;
  97         unsigned long status;
  98
  99         status = readl(p2wi->regs + P2WI_INTS);
 100         p2wi->status = status;
 101
 102         /* Clear interrupts */
 103         status &= (P2WI_INTS_LOAD_BSY | P2WI_INTS_TRANS_ERR |
 104                    P2WI_INTS_TRANS_OVER);
 105         writel(status, p2wi->regs + P2WI_INTS);
 106
 107         complete(&p2wi->complete);
 108
 109         return IRQ_HANDLED;
 110 }
 111
 112 static u32 p2wi_functionality(struct i2c_adapter *adap)
 113 {
 114         return I2C_FUNC_SMBUS_BYTE_DATA;
 115 }
 116
 117 static int p2wi_smbus_xfer(struct i2c_adapter *adap, u16 addr,
 118                            unsigned short flags, char read_write,
 119                            u8 command, int size, union i2c_smbus_data *data)
 120 {
 121         struct p2wi *p2wi = i2c_get_adapdata(adap);
 122         unsigned long dlen = P2WI_DLEN_DATA_LENGTH(1);
 123
 124         if (p2wi->slave_addr >= 0 && addr != p2wi->slave_addr) {
 125                 dev_err(&adap->dev, "invalid P2WI address\n");
 126                 return -EINVAL;
 127         }
 128
 129         if (!data)
 130                 return -EINVAL;
 131
 132         writel(command, p2wi->regs + P2WI_DADDR0);
 133
 134         if (read_write == I2C_SMBUS_READ)
 135                 dlen |= P2WI_DLEN_READ;
 136         else
 137                 writel(data->byte, p2wi->regs + P2WI_DATA0);
 138
 139         writel(dlen, p2wi->regs + P2WI_DLEN);
 140
 141         if (readl(p2wi->regs + P2WI_CTRL) & P2WI_CTRL_START_TRANS) {
 142                 dev_err(&adap->dev, "P2WI bus busy\n");
 143                 return -EBUSY;
 144         }
 145
 146         reinit_completion(&p2wi->complete);
 147
 148         writel(P2WI_INTS_LOAD_BSY | P2WI_INTS_TRANS_ERR | P2WI_INTS_TRANS_OVER,
 149                p2wi->regs + P2WI_INTE);
 150
 151         writel(P2WI_CTRL_START_TRANS | P2WI_CTRL_GLOBAL_INT_ENB,
 152                p2wi->regs + P2WI_CTRL);
 153
 154         wait_for_completion(&p2wi->complete);
 155
 156         if (p2wi->status & P2WI_INTS_LOAD_BSY) {
 157                 dev_err(&adap->dev, "P2WI bus busy\n");
 158                 return -EBUSY;
 159         }
 160
 161         if (p2wi->status & P2WI_INTS_TRANS_ERR) {
 162                 dev_err(&adap->dev, "P2WI bus xfer error\n");
 163                 return -ENXIO;
 164         }
 165
 166         if (read_write == I2C_SMBUS_READ)
 167                 data->byte = readl(p2wi->regs + P2WI_DATA0);
 168
 169         return 0;
 170 }
 171
 172 static const struct i2c_algorithm p2wi_algo = {
 173         .smbus_xfer = p2wi_smbus_xfer,
 174         .functionality = p2wi_functionality,
 175 };
 176
 177 static const struct of_device_id p2wi_of_match_table[] = {
 178         { .compatible = "allwinner,sun6i-a31-p2wi" },
 179         {}
 180 };
 181 MODULE_DEVICE_TABLE(of, p2wi_of_match_table);
 182
 183 static int p2wi_probe(struct platform_device *pdev)
 184 {
 185         struct device *dev = &pdev->dev;
 186         struct device_node *np = dev->of_node;
 187         struct device_node *childnp;
 188         unsigned long parent_clk_freq;
 189         u32 clk_freq = I2C_MAX_STANDARD_MODE_FREQ;
 190         struct p2wi *p2wi;
 191         u32 slave_addr;
 192         int clk_div;
 193         int irq;
 194         int ret;
 195
 196         of_property_read_u32(np, "clock-frequency", &clk_freq);
 197         if (clk_freq > P2WI_MAX_FREQ) {
 198                 dev_err(dev,
 199                         "required clock-frequency (%u Hz) is too high (max = 6MHz)",
 200                         clk_freq);
 201                 return -EINVAL;
 202         }
 203
 204         if (of_get_child_count(np) > 1) {
 205                 dev_err(dev, "P2WI only supports one slave device\n");
 206                 return -EINVAL;
 207         }
 208
 209         p2wi = devm_kzalloc(dev, sizeof(struct p2wi), GFP_KERNEL);
 210         if (!p2wi)
 211                 return -ENOMEM;
 212
 213         p2wi->slave_addr = -1;
 214
 215         /*
 216          * Authorize a p2wi node without any children to be able to use an
 217          * i2c-dev from userpace.
 218          * In this case the slave_addr is set to -1 and won't be checked when
 219          * launching a P2WI transfer.
 220          */
 221         childnp = of_get_next_available_child(np, NULL);
 222         if (childnp) {
 223                 ret = of_property_read_u32(childnp, "reg", &slave_addr);
 224                 if (ret) {
 225                         dev_err(dev, "invalid slave address on node %pOF\n",
 226                                 childnp);
 227                         return -EINVAL;
 228                 }
 229
 230                 p2wi->slave_addr = slave_addr;
 231         }
 232
 233         p2wi->regs = devm_platform_ioremap_resource(pdev, 0);
 234         if (IS_ERR(p2wi->regs))
 235                 return PTR_ERR(p2wi->regs);
 236
 237         strscpy(p2wi->adapter.name, pdev->name, sizeof(p2wi->adapter.name));
 238         irq = platform_get_irq(pdev, 0);
 239         if (irq < 0)
 240                 return irq;
 241
 242         p2wi->clk = devm_clk_get(dev, NULL);
 243         if (IS_ERR(p2wi->clk)) {
 244                 ret = PTR_ERR(p2wi->clk);
 245                 dev_err(dev, "failed to retrieve clk: %d\n", ret);
 246                 return ret;
 247         }
 248
 249         ret = clk_prepare_enable(p2wi->clk);
 250         if (ret) {
 251                 dev_err(dev, "failed to enable clk: %d\n", ret);
 252                 return ret;
 253         }
 254
 255         parent_clk_freq = clk_get_rate(p2wi->clk);
 256
 257         p2wi->rstc = devm_reset_control_get_exclusive(dev, NULL);
 258         if (IS_ERR(p2wi->rstc)) {
 259                 ret = PTR_ERR(p2wi->rstc);
 260                 dev_err(dev, "failed to retrieve reset controller: %d\n", ret);
 261                 goto err_clk_disable;
 262         }
 263
 264         ret = reset_control_deassert(p2wi->rstc);
 265         if (ret) {
 266                 dev_err(dev, "failed to deassert reset line: %d\n", ret);
 267                 goto err_clk_disable;
 268         }
 269
 270         init_completion(&p2wi->complete);
 271         p2wi->adapter.dev.parent = dev;
 272         p2wi->adapter.algo = &p2wi_algo;
 273         p2wi->adapter.owner = THIS_MODULE;
 274         p2wi->adapter.dev.of_node = pdev->dev.of_node;
 275         platform_set_drvdata(pdev, p2wi);
 276         i2c_set_adapdata(&p2wi->adapter, p2wi);
 277
 278         ret = devm_request_irq(dev, irq, p2wi_interrupt, 0, pdev->name, p2wi);
 279         if (ret) {
 280                 dev_err(dev, "can't register interrupt handler irq%d: %d\n",
 281                         irq, ret);
 282                 goto err_reset_assert;
 283         }
 284
 285         writel(P2WI_CTRL_SOFT_RST, p2wi->regs + P2WI_CTRL);
 286
 287         clk_div = parent_clk_freq / clk_freq;
 288         if (!clk_div) {
 289                 dev_warn(dev,
 290                          "clock-frequency is too high, setting it to %lu Hz\n",
 291                          parent_clk_freq);
 292                 clk_div = 1;
 293         } else if (clk_div > P2WI_CCR_MAX_CLK_DIV) {
 294                 dev_warn(dev,
 295                          "clock-frequency is too low, setting it to %lu Hz\n",
 296                          parent_clk_freq / P2WI_CCR_MAX_CLK_DIV);
 297                 clk_div = P2WI_CCR_MAX_CLK_DIV;
 298         }
 299
 300         writel(P2WI_CCR_SDA_OUT_DELAY(1) | P2WI_CCR_CLK_DIV(clk_div),
 301                p2wi->regs + P2WI_CCR);
 302
 303         ret = i2c_add_adapter(&p2wi->adapter);
 304         if (!ret)
 305                 return 0;
 306
 307 err_reset_assert:
 308         reset_control_assert(p2wi->rstc);
 309
 310 err_clk_disable:
 311         clk_disable_unprepare(p2wi->clk);
 312
 313         return ret;
 314 }
 315
 316 static int p2wi_remove(struct platform_device *dev)
 317 {
 318         struct p2wi *p2wi = platform_get_drvdata(dev);
 319
 320         reset_control_assert(p2wi->rstc);
 321         clk_disable_unprepare(p2wi->clk);
 322         i2c_del_adapter(&p2wi->adapter);
 323
 324         return 0;
 325 }
 326
 327 static struct platform_driver p2wi_driver = {
 328         .probe  = p2wi_probe,
 329         .remove = p2wi_remove,
 330         .driver = {
 331                 .name = "i2c-sunxi-p2wi",
 332                 .of_match_table = p2wi_of_match_table,
 333         },
 334 };
 335 module_platform_driver(p2wi_driver);
 336
 337 MODULE_AUTHOR("Boris BREZILLON <boris.brezillon@free-electrons.com>");
 338 MODULE_DESCRIPTION("Allwinner P2WI driver");
 339 MODULE_LICENSE("GPL v2");