1 files changed, 535 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
new file mode 100644
index 0000000000..b92de19442
--- /dev/null
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -0,0 +1,535 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * BCM2835 master mode driver
+ */
+
+#include <linux/clk.h>
+#include <linux/clkdev.h>
+#include <linux/clk-provider.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/of.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;
+	int irq;
+	struct i2c_adapter adapter;
+	struct completion completion;
+	struct i2c_msg *curr_msg;
+	struct clk *bus_clk;
+	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);
+}
+
+#define to_clk_bcm2835_i2c(_hw) container_of(_hw, struct clk_bcm2835_i2c, hw)
+struct clk_bcm2835_i2c {
+	struct clk_hw hw;
+	struct bcm2835_i2c_dev *i2c_dev;
+};
+
+static int clk_bcm2835_i2c_calc_divider(unsigned long rate,
+				unsigned long parent_rate)
+{
+	u32 divider = DIV_ROUND_UP(parent_rate, 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))
+		return -EINVAL;
+
+	return divider;
+}
+
+static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate,
+				unsigned long parent_rate)
+{
+	struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
+	u32 redl, fedl;
+	u32 divider = clk_bcm2835_i2c_calc_divider(rate, parent_rate);
+
+	if (divider == -EINVAL)
+		return -EINVAL;
+
+	bcm2835_i2c_writel(div->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(div->i2c_dev, BCM2835_I2C_DEL,
+			   (fedl << BCM2835_I2C_FEDL_SHIFT) |
+			   (redl << BCM2835_I2C_REDL_SHIFT));
+	return 0;
+}
+
+static long clk_bcm2835_i2c_round_rate(struct clk_hw *hw, unsigned long rate,
+				unsigned long *parent_rate)
+{
+	u32 divider = clk_bcm2835_i2c_calc_divider(rate, *parent_rate);
+
+	return DIV_ROUND_UP(*parent_rate, divider);
+}
+
+static unsigned long clk_bcm2835_i2c_recalc_rate(struct clk_hw *hw,
+						unsigned long parent_rate)
+{
+	struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
+	u32 divider = bcm2835_i2c_readl(div->i2c_dev, BCM2835_I2C_DIV);
+
+	return DIV_ROUND_UP(parent_rate, divider);
+}
+
+static const struct clk_ops clk_bcm2835_i2c_ops = {
+	.set_rate = clk_bcm2835_i2c_set_rate,
+	.round_rate = clk_bcm2835_i2c_round_rate,
+	.recalc_rate = clk_bcm2835_i2c_recalc_rate,
+};
+
+static struct clk *bcm2835_i2c_register_div(struct device *dev,
+					struct clk *mclk,
+					struct bcm2835_i2c_dev *i2c_dev)
+{
+	struct clk_init_data init;
+	struct clk_bcm2835_i2c *priv;
+	char name[32];
+	const char *mclk_name;
+
+	snprintf(name, sizeof(name), "%s_div", dev_name(dev));
+
+	mclk_name = __clk_get_name(mclk);
+
+	init.ops = &clk_bcm2835_i2c_ops;
+	init.name = name;
+	init.parent_names = (const char* []) { mclk_name };
+	init.num_parents = 1;
+	init.flags = 0;
+
+	priv = devm_kzalloc(dev, sizeof(struct clk_bcm2835_i2c), GFP_KERNEL);
+	if (priv == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	priv->hw.init = &init;
+	priv->i2c_dev = i2c_dev;
+
+	clk_hw_register_clkdev(&priv->hw, "div", dev_name(dev));
+	return devm_clk_register(dev, &priv->hw);
+}
+
+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;
+
+	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;
+		}
+
+	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,
+};
+
+/*
+ * The BCM2835 was reported to have problems with clock stretching:
+ * https://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;
+	int ret;
+	struct i2c_adapter *adap;
+	struct clk *mclk;
+	u32 bus_clk_rate;
+
+	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);
+
+	i2c_dev->regs = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(i2c_dev->regs))
+		return PTR_ERR(i2c_dev->regs);
+
+	mclk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(mclk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(mclk),
+				     "Could not get clock\n");
+
+	i2c_dev->bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk, i2c_dev);
+
+	if (IS_ERR(i2c_dev->bus_clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(i2c_dev->bus_clk),
+				     "Could not register clock\n");
+
+	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
+				   &bus_clk_rate);
+	if (ret < 0) {
+		dev_warn(&pdev->dev,
+			 "Could not read clock-frequency property\n");
+		bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ;
+	}
+
+	ret = clk_set_rate_exclusive(i2c_dev->bus_clk, bus_clk_rate);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, ret,
+				     "Could not set clock frequency\n");
+
+	ret = clk_prepare_enable(i2c_dev->bus_clk);
+	if (ret) {
+		dev_err(&pdev->dev, "Couldn't prepare clock");
+		goto err_put_exclusive_rate;
+	}
+
+	i2c_dev->irq = platform_get_irq(pdev, 0);
+	if (i2c_dev->irq < 0) {
+		ret = i2c_dev->irq;
+		goto err_disable_unprepare_clk;
+	}
+
+	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");
+		goto err_disable_unprepare_clk;
+	}
+
+	adap = &i2c_dev->adapter;
+	i2c_set_adapdata(adap, i2c_dev);
+	adap->owner = THIS_MODULE;
+	adap->class = I2C_CLASS_DEPRECATED;
+	snprintf(adap->name, sizeof(adap->name), "bcm2835 (%s)",
+		 of_node_full_name(pdev->dev.of_node));
+	adap->algo = &bcm2835_i2c_algo;
+	adap->dev.parent = &pdev->dev;
+	adap->dev.of_node = pdev->dev.of_node;
+	adap->quirks = of_device_get_match_data(&pdev->dev);
+
+	/*
+	 * 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)
+		goto err_free_irq;
+
+	return 0;
+
+err_free_irq:
+	free_irq(i2c_dev->irq, i2c_dev);
+err_disable_unprepare_clk:
+	clk_disable_unprepare(i2c_dev->bus_clk);
+err_put_exclusive_rate:
+	clk_rate_exclusive_put(i2c_dev->bus_clk);
+
+	return ret;
+}
+
+static void bcm2835_i2c_remove(struct platform_device *pdev)
+{
+	struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
+
+	clk_rate_exclusive_put(i2c_dev->bus_clk);
+	clk_disable_unprepare(i2c_dev->bus_clk);
+
+	free_irq(i2c_dev->irq, i2c_dev);
+	i2c_del_adapter(&i2c_dev->adapter);
+}
+
+static const struct of_device_id bcm2835_i2c_of_match[] = {
+	{ .compatible = "brcm,bcm2711-i2c" },
+	{ .compatible = "brcm,bcm2835-i2c", .data = &bcm2835_i2c_quirks },
+	{},
+};
+MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
+
+static struct platform_driver bcm2835_i2c_driver = {
+	.probe		= bcm2835_i2c_probe,
+	.remove_new	= 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");