diff options
Diffstat (limited to 'drivers/i2c/busses/i2c-bcm2835.c')
| -rw-r--r-- | drivers/i2c/busses/i2c-bcm2835.c | 450 |
1 files changed, 450 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c new file mode 100644 index 000000000..db1ab9ccc --- /dev/null +++ b/drivers/i2c/busses/i2c-bcm2835.c @@ -0,0 +1,450 @@ +/* + * BCM2835 master mode driver + * + * This software is licensed under the terms of the GNU General Public + * License version 2, as published by the Free Software Foundation, and + * may be copied, distributed, and modified under those terms. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <linux/clk.h> +#include <linux/completion.h> +#include <linux/err.h> +#include <linux/i2c.h> +#include <linux/interrupt.h> +#include <linux/io.h> +#include <linux/module.h> +#include <linux/platform_device.h> +#include <linux/slab.h> + +#define BCM2835_I2C_C 0x0 +#define BCM2835_I2C_S 0x4 +#define BCM2835_I2C_DLEN 0x8 +#define BCM2835_I2C_A 0xc +#define BCM2835_I2C_FIFO 0x10 +#define BCM2835_I2C_DIV 0x14 +#define BCM2835_I2C_DEL 0x18 +/* + * 16-bit field for the number of SCL cycles to wait after rising SCL + * before deciding the slave is not responding. 0 disables the + * timeout detection. + */ +#define BCM2835_I2C_CLKT 0x1c + +#define BCM2835_I2C_C_READ BIT(0) +#define BCM2835_I2C_C_CLEAR BIT(4) /* bits 4 and 5 both clear */ +#define BCM2835_I2C_C_ST BIT(7) +#define BCM2835_I2C_C_INTD BIT(8) +#define BCM2835_I2C_C_INTT BIT(9) +#define BCM2835_I2C_C_INTR BIT(10) +#define BCM2835_I2C_C_I2CEN BIT(15) + +#define BCM2835_I2C_S_TA BIT(0) +#define BCM2835_I2C_S_DONE BIT(1) +#define BCM2835_I2C_S_TXW BIT(2) +#define BCM2835_I2C_S_RXR BIT(3) +#define BCM2835_I2C_S_TXD BIT(4) +#define BCM2835_I2C_S_RXD BIT(5) +#define BCM2835_I2C_S_TXE BIT(6) +#define BCM2835_I2C_S_RXF BIT(7) +#define BCM2835_I2C_S_ERR BIT(8) +#define BCM2835_I2C_S_CLKT BIT(9) +#define BCM2835_I2C_S_LEN BIT(10) /* Fake bit for SW error reporting */ + +#define BCM2835_I2C_FEDL_SHIFT 16 +#define BCM2835_I2C_REDL_SHIFT 0 + +#define BCM2835_I2C_CDIV_MIN 0x0002 +#define BCM2835_I2C_CDIV_MAX 0xFFFE + +struct bcm2835_i2c_dev { + struct device *dev; + void __iomem *regs; + struct clk *clk; + int irq; + u32 bus_clk_rate; + struct i2c_adapter adapter; + struct completion completion; + struct i2c_msg *curr_msg; + int num_msgs; + u32 msg_err; + u8 *msg_buf; + size_t msg_buf_remaining; +}; + +static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev, + u32 reg, u32 val) +{ + writel(val, i2c_dev->regs + reg); +} + +static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg) +{ + return readl(i2c_dev->regs + reg); +} + +static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev) +{ + u32 divider, redl, fedl; + + divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), + i2c_dev->bus_clk_rate); + /* + * Per the datasheet, the register is always interpreted as an even + * number, by rounding down. In other words, the LSB is ignored. So, + * if the LSB is set, increment the divider to avoid any issue. + */ + if (divider & 1) + divider++; + if ((divider < BCM2835_I2C_CDIV_MIN) || + (divider > BCM2835_I2C_CDIV_MAX)) { + dev_err_ratelimited(i2c_dev->dev, "Invalid clock-frequency\n"); + return -EINVAL; + } + + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider); + + /* + * Number of core clocks to wait after falling edge before + * outputting the next data bit. Note that both FEDL and REDL + * can't be greater than CDIV/2. + */ + fedl = max(divider / 16, 1u); + + /* + * Number of core clocks to wait after rising edge before + * sampling the next incoming data bit. + */ + redl = max(divider / 4, 1u); + + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DEL, + (fedl << BCM2835_I2C_FEDL_SHIFT) | + (redl << BCM2835_I2C_REDL_SHIFT)); + return 0; +} + +static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev) +{ + u32 val; + + while (i2c_dev->msg_buf_remaining) { + val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); + if (!(val & BCM2835_I2C_S_TXD)) + break; + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO, + *i2c_dev->msg_buf); + i2c_dev->msg_buf++; + i2c_dev->msg_buf_remaining--; + } +} + +static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev) +{ + u32 val; + + while (i2c_dev->msg_buf_remaining) { + val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); + if (!(val & BCM2835_I2C_S_RXD)) + break; + *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev, + BCM2835_I2C_FIFO); + i2c_dev->msg_buf++; + i2c_dev->msg_buf_remaining--; + } +} + +/* + * Repeated Start Condition (Sr) + * The BCM2835 ARM Peripherals datasheet mentions a way to trigger a Sr when it + * talks about reading from a slave with 10 bit address. This is achieved by + * issuing a write, poll the I2CS.TA flag and wait for it to be set, and then + * issue a read. + * A comment in https://github.com/raspberrypi/linux/issues/254 shows how the + * firmware actually does it using polling and says that it's a workaround for + * a problem in the state machine. + * It turns out that it is possible to use the TXW interrupt to know when the + * transfer is active, provided the FIFO has not been prefilled. + */ + +static void bcm2835_i2c_start_transfer(struct bcm2835_i2c_dev *i2c_dev) +{ + u32 c = BCM2835_I2C_C_ST | BCM2835_I2C_C_I2CEN; + struct i2c_msg *msg = i2c_dev->curr_msg; + bool last_msg = (i2c_dev->num_msgs == 1); + + if (!i2c_dev->num_msgs) + return; + + i2c_dev->num_msgs--; + i2c_dev->msg_buf = msg->buf; + i2c_dev->msg_buf_remaining = msg->len; + + if (msg->flags & I2C_M_RD) + c |= BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR; + else + c |= BCM2835_I2C_C_INTT; + + if (last_msg) + c |= BCM2835_I2C_C_INTD; + + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr); + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len); + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c); +} + +static void bcm2835_i2c_finish_transfer(struct bcm2835_i2c_dev *i2c_dev) +{ + i2c_dev->curr_msg = NULL; + i2c_dev->num_msgs = 0; + + i2c_dev->msg_buf = NULL; + i2c_dev->msg_buf_remaining = 0; +} + +/* + * Note about I2C_C_CLEAR on error: + * The I2C_C_CLEAR on errors will take some time to resolve -- if you were in + * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through + * the state machine to send a NACK and a STOP. Since we're setting CLEAR + * without I2CEN, that NACK will be hanging around queued up for next time + * we start the engine. + */ + +static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data) +{ + struct bcm2835_i2c_dev *i2c_dev = data; + u32 val, err; + + val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); + + err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR); + if (err) { + i2c_dev->msg_err = err; + goto complete; + } + + if (val & BCM2835_I2C_S_DONE) { + if (!i2c_dev->curr_msg) { + dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n"); + } else if (i2c_dev->curr_msg->flags & I2C_M_RD) { + bcm2835_drain_rxfifo(i2c_dev); + val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); + } + + if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining) + i2c_dev->msg_err = BCM2835_I2C_S_LEN; + else + i2c_dev->msg_err = 0; + goto complete; + } + + if (val & BCM2835_I2C_S_TXW) { + if (!i2c_dev->msg_buf_remaining) { + i2c_dev->msg_err = val | BCM2835_I2C_S_LEN; + goto complete; + } + + bcm2835_fill_txfifo(i2c_dev); + + if (i2c_dev->num_msgs && !i2c_dev->msg_buf_remaining) { + i2c_dev->curr_msg++; + bcm2835_i2c_start_transfer(i2c_dev); + } + + return IRQ_HANDLED; + } + + if (val & BCM2835_I2C_S_RXR) { + if (!i2c_dev->msg_buf_remaining) { + i2c_dev->msg_err = val | BCM2835_I2C_S_LEN; + goto complete; + } + + bcm2835_drain_rxfifo(i2c_dev); + return IRQ_HANDLED; + } + + return IRQ_NONE; + +complete: + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR); + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, BCM2835_I2C_S_CLKT | + BCM2835_I2C_S_ERR | BCM2835_I2C_S_DONE); + complete(&i2c_dev->completion); + + return IRQ_HANDLED; +} + +static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], + int num) +{ + struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap); + unsigned long time_left; + int i, ret; + + for (i = 0; i < (num - 1); i++) + if (msgs[i].flags & I2C_M_RD) { + dev_warn_once(i2c_dev->dev, + "only one read message supported, has to be last\n"); + return -EOPNOTSUPP; + } + + ret = bcm2835_i2c_set_divider(i2c_dev); + if (ret) + return ret; + + i2c_dev->curr_msg = msgs; + i2c_dev->num_msgs = num; + reinit_completion(&i2c_dev->completion); + + bcm2835_i2c_start_transfer(i2c_dev); + + time_left = wait_for_completion_timeout(&i2c_dev->completion, + adap->timeout); + + bcm2835_i2c_finish_transfer(i2c_dev); + + if (!time_left) { + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, + BCM2835_I2C_C_CLEAR); + dev_err(i2c_dev->dev, "i2c transfer timed out\n"); + return -ETIMEDOUT; + } + + if (!i2c_dev->msg_err) + return num; + + dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err); + + if (i2c_dev->msg_err & BCM2835_I2C_S_ERR) + return -EREMOTEIO; + + return -EIO; +} + +static u32 bcm2835_i2c_func(struct i2c_adapter *adap) +{ + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; +} + +static const struct i2c_algorithm bcm2835_i2c_algo = { + .master_xfer = bcm2835_i2c_xfer, + .functionality = bcm2835_i2c_func, +}; + +/* + * This HW was reported to have problems with clock stretching: + * http://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html + * https://www.raspberrypi.org/forums/viewtopic.php?p=146272 + */ +static const struct i2c_adapter_quirks bcm2835_i2c_quirks = { + .flags = I2C_AQ_NO_CLK_STRETCH, +}; + +static int bcm2835_i2c_probe(struct platform_device *pdev) +{ + struct bcm2835_i2c_dev *i2c_dev; + struct resource *mem, *irq; + int ret; + struct i2c_adapter *adap; + + i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL); + if (!i2c_dev) + return -ENOMEM; + platform_set_drvdata(pdev, i2c_dev); + i2c_dev->dev = &pdev->dev; + init_completion(&i2c_dev->completion); + + mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); + i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem); + if (IS_ERR(i2c_dev->regs)) + return PTR_ERR(i2c_dev->regs); + + i2c_dev->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(i2c_dev->clk)) { + if (PTR_ERR(i2c_dev->clk) != -EPROBE_DEFER) + dev_err(&pdev->dev, "Could not get clock\n"); + return PTR_ERR(i2c_dev->clk); + } + + ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency", + &i2c_dev->bus_clk_rate); + if (ret < 0) { + dev_warn(&pdev->dev, + "Could not read clock-frequency property\n"); + i2c_dev->bus_clk_rate = 100000; + } + + irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0); + if (!irq) { + dev_err(&pdev->dev, "No IRQ resource\n"); + return -ENODEV; + } + i2c_dev->irq = irq->start; + + ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED, + dev_name(&pdev->dev), i2c_dev); + if (ret) { + dev_err(&pdev->dev, "Could not request IRQ\n"); + return -ENODEV; + } + + adap = &i2c_dev->adapter; + i2c_set_adapdata(adap, i2c_dev); + adap->owner = THIS_MODULE; + adap->class = I2C_CLASS_DEPRECATED; + strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name)); + adap->algo = &bcm2835_i2c_algo; + adap->dev.parent = &pdev->dev; + adap->dev.of_node = pdev->dev.of_node; + adap->quirks = &bcm2835_i2c_quirks; + + /* + * Disable the hardware clock stretching timeout. SMBUS + * specifies a limit for how long the device can stretch the + * clock, but core I2C doesn't. + */ + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_CLKT, 0); + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0); + + ret = i2c_add_adapter(adap); + if (ret) + free_irq(i2c_dev->irq, i2c_dev); + + return ret; +} + +static int bcm2835_i2c_remove(struct platform_device *pdev) +{ + struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev); + + free_irq(i2c_dev->irq, i2c_dev); + i2c_del_adapter(&i2c_dev->adapter); + + return 0; +} + +static const struct of_device_id bcm2835_i2c_of_match[] = { + { .compatible = "brcm,bcm2835-i2c" }, + {}, +}; +MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match); + +static struct platform_driver bcm2835_i2c_driver = { + .probe = bcm2835_i2c_probe, + .remove = bcm2835_i2c_remove, + .driver = { + .name = "i2c-bcm2835", + .of_match_table = bcm2835_i2c_of_match, + }, +}; +module_platform_driver(bcm2835_i2c_driver); + +MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>"); +MODULE_DESCRIPTION("BCM2835 I2C bus adapter"); +MODULE_LICENSE("GPL v2"); +MODULE_ALIAS("platform:i2c-bcm2835"); |