i2c: axxia: Add I2C driver for AXM55xx

Add I2C bus driver for the controller found in the LSI Axxia family SoCs. The
driver implements 10-bit addressing and SMBus transfer modes via emulation
(including SMBus block data read).

Signed-off-by: Anders Berg <[e-mail]>
Signed-off-by: Wolfram Sang <[e-mail]>

Documentation/devicetree/bindings/i2c/i2c-axxia.txt

···
+LSI Axxia I2C
+
+Required properties :
+- compatible : Must be "lsi,api2c"
+- reg : Offset and length of the register set for the device
+- interrupts : the interrupt specifier
+- #address-cells : Must be <1>;
+- #size-cells : Must be <0>;
+- clock-names : Must contain "i2c".
+- clocks: Must contain an entry for each name in clock-names. See the common
+  clock bindings.
+
+Optional properties :
+- clock-frequency : Desired I2C bus clock frequency in Hz. If not specified,
+  the default 100 kHz frequency will be used. As only Normal and Fast modes
+  are supported, possible values are 100000 and 400000.
+
+Example :
+
+i2c@02010084000 {
+	compatible = "lsi,api2c";
+	device_type = "i2c";
+	#address-cells = <1>;
+	#size-cells = <0>;
+	reg = <0x20 0x10084000 0x00 0x1000>;
+	interrupts = <0 19 4>;
+	clocks = <&clk_per>;
+	clock-names = "i2c";
+	clock-frequency = <400000>;
+};

drivers/i2c/busses/Kconfig

···
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-au1550.
 
+config I2C_AXXIA
+	tristate "Axxia I2C controller"
+	depends on ARCH_AXXIA || COMPILE_TEST
+	default ARCH_AXXIA
+	help
+	  Say yes if you want to support the I2C bus on Axxia platforms.
+
+	  Please note that this controller is limited to transfers of maximum
+	  255 bytes in length. Any attempt to to a larger transfer will return
+	  an error.
+
 config I2C_BCM2835
 	tristate "Broadcom BCM2835 I2C controller"
 	depends on ARCH_BCM2835

drivers/i2c/busses/Makefile

···
 # Embedded system I2C/SMBus host controller drivers
 obj-$(CONFIG_I2C_AT91)		+= i2c-at91.o
 obj-$(CONFIG_I2C_AU1550)	+= i2c-au1550.o
+obj-$(CONFIG_I2C_AXXIA)		+= i2c-axxia.o
 obj-$(CONFIG_I2C_BCM2835)	+= i2c-bcm2835.o
 obj-$(CONFIG_I2C_BLACKFIN_TWI)	+= i2c-bfin-twi.o
 obj-$(CONFIG_I2C_CADENCE)	+= i2c-cadence.o

drivers/i2c/busses/i2c-axxia.c

···
+/*
+ * This driver implements I2C master functionality using the LSI API2C
+ * controller.
+ *
+ * NOTE: The controller has a limitation in that it can only do transfers of
+ * maximum 255 bytes at a time. If a larger transfer is attempted, error code
+ * (-EINVAL) is returned.
+ *
+ * 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.
+ */
+#include <linux/clk.h>
+#include <linux/clkdev.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+
+#define SCL_WAIT_TIMEOUT_NS 25000000
+#define I2C_XFER_TIMEOUT    (msecs_to_jiffies(250))
+#define I2C_STOP_TIMEOUT    (msecs_to_jiffies(100))
+#define FIFO_SIZE           8
+
+#define GLOBAL_CONTROL		0x00
+#define   GLOBAL_MST_EN         BIT(0)
+#define   GLOBAL_SLV_EN         BIT(1)
+#define   GLOBAL_IBML_EN        BIT(2)
+#define INTERRUPT_STATUS	0x04
+#define INTERRUPT_ENABLE	0x08
+#define   INT_SLV               BIT(1)
+#define   INT_MST               BIT(0)
+#define WAIT_TIMER_CONTROL	0x0c
+#define   WT_EN			BIT(15)
+#define   WT_VALUE(_x)		((_x) & 0x7fff)
+#define IBML_TIMEOUT		0x10
+#define IBML_LOW_MEXT		0x14
+#define IBML_LOW_SEXT		0x18
+#define TIMER_CLOCK_DIV		0x1c
+#define I2C_BUS_MONITOR		0x20
+#define SOFT_RESET		0x24
+#define MST_COMMAND		0x28
+#define   CMD_BUSY		(1<<3)
+#define   CMD_MANUAL		(0x00 | CMD_BUSY)
+#define   CMD_AUTO		(0x01 | CMD_BUSY)
+#define MST_RX_XFER		0x2c
+#define MST_TX_XFER		0x30
+#define MST_ADDR_1		0x34
+#define MST_ADDR_2		0x38
+#define MST_DATA		0x3c
+#define MST_TX_FIFO		0x40
+#define MST_RX_FIFO		0x44
+#define MST_INT_ENABLE		0x48
+#define MST_INT_STATUS		0x4c
+#define   MST_STATUS_RFL	(1 << 13) /* RX FIFO serivce */
+#define   MST_STATUS_TFL	(1 << 12) /* TX FIFO service */
+#define   MST_STATUS_SNS	(1 << 11) /* Manual mode done */
+#define   MST_STATUS_SS		(1 << 10) /* Automatic mode done */
+#define   MST_STATUS_SCC	(1 << 9)  /* Stop complete */
+#define   MST_STATUS_IP		(1 << 8)  /* Invalid parameter */
+#define   MST_STATUS_TSS	(1 << 7)  /* Timeout */
+#define   MST_STATUS_AL		(1 << 6)  /* Arbitration lost */
+#define   MST_STATUS_ND		(1 << 5)  /* NAK on data phase */
+#define   MST_STATUS_NA		(1 << 4)  /* NAK on address phase */
+#define   MST_STATUS_NAK	(MST_STATUS_NA | \
+				 MST_STATUS_ND)
+#define   MST_STATUS_ERR	(MST_STATUS_NAK | \
+				 MST_STATUS_AL  | \
+				 MST_STATUS_IP  | \
+				 MST_STATUS_TSS)
+#define MST_TX_BYTES_XFRD	0x50
+#define MST_RX_BYTES_XFRD	0x54
+#define SCL_HIGH_PERIOD		0x80
+#define SCL_LOW_PERIOD		0x84
+#define SPIKE_FLTR_LEN		0x88
+#define SDA_SETUP_TIME		0x8c
+#define SDA_HOLD_TIME		0x90
+
+/**
+ * axxia_i2c_dev - I2C device context
+ * @base: pointer to register struct
+ * @msg: pointer to current message
+ * @msg_xfrd: number of bytes transferred in msg
+ * @msg_err: error code for completed message
+ * @msg_complete: xfer completion object
+ * @dev: device reference
+ * @adapter: core i2c abstraction
+ * @i2c_clk: clock reference for i2c input clock
+ * @bus_clk_rate: current i2c bus clock rate
+ */
+struct axxia_i2c_dev {
+	void __iomem *base;
+	struct i2c_msg *msg;
+	size_t msg_xfrd;
+	int msg_err;
+	struct completion msg_complete;
+	struct device *dev;
+	struct i2c_adapter adapter;
+	struct clk *i2c_clk;
+	u32 bus_clk_rate;
+};
+
+static void i2c_int_disable(struct axxia_i2c_dev *idev, u32 mask)
+{
+	u32 int_en;
+
+	int_en = readl(idev->base + MST_INT_ENABLE);
+	writel(int_en & ~mask, idev->base + MST_INT_ENABLE);
+}
+
+static void i2c_int_enable(struct axxia_i2c_dev *idev, u32 mask)
+{
+	u32 int_en;
+
+	int_en = readl(idev->base + MST_INT_ENABLE);
+	writel(int_en | mask, idev->base + MST_INT_ENABLE);
+}
+
+/**
+ * ns_to_clk - Convert time (ns) to clock cycles for the given clock frequency.
+ */
+static u32 ns_to_clk(u64 ns, u32 clk_mhz)
+{
+	return div_u64(ns * clk_mhz, 1000);
+}
+
+static int axxia_i2c_init(struct axxia_i2c_dev *idev)
+{
+	u32 divisor = clk_get_rate(idev->i2c_clk) / idev->bus_clk_rate;
+	u32 clk_mhz = clk_get_rate(idev->i2c_clk) / 1000000;
+	u32 t_setup;
+	u32 t_high, t_low;
+	u32 tmo_clk;
+	u32 prescale;
+	unsigned long timeout;
+
+	dev_dbg(idev->dev, "rate=%uHz per_clk=%uMHz -> ratio=1:%u\n",
+		idev->bus_clk_rate, clk_mhz, divisor);
+
+	/* Reset controller */
+	writel(0x01, idev->base + SOFT_RESET);
+	timeout = jiffies + msecs_to_jiffies(100);
+	while (readl(idev->base + SOFT_RESET) & 1) {
+		if (time_after(jiffies, timeout)) {
+			dev_warn(idev->dev, "Soft reset failed\n");
+			break;
+		}
+	}
+
+	/* Enable Master Mode */
+	writel(0x1, idev->base + GLOBAL_CONTROL);
+
+	if (idev->bus_clk_rate <= 100000) {
+		/* Standard mode SCL 50/50, tSU:DAT = 250 ns */
+		t_high = divisor * 1 / 2;
+		t_low = divisor * 1 / 2;
+		t_setup = ns_to_clk(250, clk_mhz);
+	} else {
+		/* Fast mode SCL 33/66, tSU:DAT = 100 ns */
+		t_high = divisor * 1 / 3;
+		t_low = divisor * 2 / 3;
+		t_setup = ns_to_clk(100, clk_mhz);
+	}
+
+	/* SCL High Time */
+	writel(t_high, idev->base + SCL_HIGH_PERIOD);
+	/* SCL Low Time */
+	writel(t_low, idev->base + SCL_LOW_PERIOD);
+	/* SDA Setup Time */
+	writel(t_setup, idev->base + SDA_SETUP_TIME);
+	/* SDA Hold Time, 300ns */
+	writel(ns_to_clk(300, clk_mhz), idev->base + SDA_HOLD_TIME);
+	/* Filter <50ns spikes */
+	writel(ns_to_clk(50, clk_mhz), idev->base + SPIKE_FLTR_LEN);
+
+	/* Configure Time-Out Registers */
+	tmo_clk = ns_to_clk(SCL_WAIT_TIMEOUT_NS, clk_mhz);
+
+	/* Find prescaler value that makes tmo_clk fit in 15-bits counter. */
+	for (prescale = 0; prescale < 15; ++prescale) {
+		if (tmo_clk <= 0x7fff)
+			break;
+		tmo_clk >>= 1;
+	}
+	if (tmo_clk > 0x7fff)
+		tmo_clk = 0x7fff;
+
+	/* Prescale divider (log2) */
+	writel(prescale, idev->base + TIMER_CLOCK_DIV);
+	/* Timeout in divided clocks */
+	writel(WT_EN | WT_VALUE(tmo_clk), idev->base + WAIT_TIMER_CONTROL);
+
+	/* Mask all master interrupt bits */
+	i2c_int_disable(idev, ~0);
+
+	/* Interrupt enable */
+	writel(0x01, idev->base + INTERRUPT_ENABLE);
+
+	return 0;
+}
+
+static int i2c_m_rd(const struct i2c_msg *msg)
+{
+	return (msg->flags & I2C_M_RD) != 0;
+}
+
+static int i2c_m_ten(const struct i2c_msg *msg)
+{
+	return (msg->flags & I2C_M_TEN) != 0;
+}
+
+static int i2c_m_recv_len(const struct i2c_msg *msg)
+{
+	return (msg->flags & I2C_M_RECV_LEN) != 0;
+}
+
+/**
+ * axxia_i2c_empty_rx_fifo - Fetch data from RX FIFO and update SMBus block
+ * transfer length if this is the first byte of such a transfer.
+ */
+static int axxia_i2c_empty_rx_fifo(struct axxia_i2c_dev *idev)
+{
+	struct i2c_msg *msg = idev->msg;
+	size_t rx_fifo_avail = readl(idev->base + MST_RX_FIFO);
+	int bytes_to_transfer = min(rx_fifo_avail, msg->len - idev->msg_xfrd);
+
+	while (bytes_to_transfer-- > 0) {
+		int c = readl(idev->base + MST_DATA);
+
+		if (idev->msg_xfrd == 0 && i2c_m_recv_len(msg)) {
+			/*
+			 * Check length byte for SMBus block read
+			 */
+			if (c <= 0 || c > I2C_SMBUS_BLOCK_MAX) {
+				idev->msg_err = -EPROTO;
+				i2c_int_disable(idev, ~0);
+				complete(&idev->msg_complete);
+				break;
+			}
+			msg->len = 1 + c;
+			writel(msg->len, idev->base + MST_RX_XFER);
+		}
+		msg->buf[idev->msg_xfrd++] = c;
+	}
+
+	return 0;
+}
+
+/**
+ * axxia_i2c_fill_tx_fifo - Fill TX FIFO from current message buffer.
+ * @return: Number of bytes left to transfer.
+ */
+static int axxia_i2c_fill_tx_fifo(struct axxia_i2c_dev *idev)
+{
+	struct i2c_msg *msg = idev->msg;
+	size_t tx_fifo_avail = FIFO_SIZE - readl(idev->base + MST_TX_FIFO);
+	int bytes_to_transfer = min(tx_fifo_avail, msg->len - idev->msg_xfrd);
+	int ret = msg->len - idev->msg_xfrd - bytes_to_transfer;
+
+	while (bytes_to_transfer-- > 0)
+		writel(msg->buf[idev->msg_xfrd++], idev->base + MST_DATA);
+
+	return ret;
+}
+
+static irqreturn_t axxia_i2c_isr(int irq, void *_dev)
+{
+	struct axxia_i2c_dev *idev = _dev;
+	u32 status;
+
+	if (!(readl(idev->base + INTERRUPT_STATUS) & INT_MST))
+		return IRQ_NONE;
+
+	/* Read interrupt status bits */
+	status = readl(idev->base + MST_INT_STATUS);
+
+	if (!idev->msg) {
+		dev_warn(idev->dev, "unexpected interrupt\n");
+		goto out;
+	}
+
+	/* RX FIFO needs service? */
+	if (i2c_m_rd(idev->msg) && (status & MST_STATUS_RFL))
+		axxia_i2c_empty_rx_fifo(idev);
+
+	/* TX FIFO needs service? */
+	if (!i2c_m_rd(idev->msg) && (status & MST_STATUS_TFL)) {
+		if (axxia_i2c_fill_tx_fifo(idev) == 0)
+			i2c_int_disable(idev, MST_STATUS_TFL);
+	}
+
+	if (status & MST_STATUS_SCC) {
+		/* Stop completed */
+		i2c_int_disable(idev, ~0);
+		complete(&idev->msg_complete);
+	} else if (status & MST_STATUS_SNS) {
+		/* Transfer done */
+		i2c_int_disable(idev, ~0);
+		if (i2c_m_rd(idev->msg) && idev->msg_xfrd < idev->msg->len)
+			axxia_i2c_empty_rx_fifo(idev);
+		complete(&idev->msg_complete);
+	} else if (unlikely(status & MST_STATUS_ERR)) {
+		/* Transfer error */
+		i2c_int_disable(idev, ~0);
+		if (status & MST_STATUS_AL)
+			idev->msg_err = -EAGAIN;
+		else if (status & MST_STATUS_NAK)
+			idev->msg_err = -ENXIO;
+		else
+			idev->msg_err = -EIO;
+		dev_dbg(idev->dev, "error %#x, addr=%#x rx=%u/%u tx=%u/%u\n",
+			status,
+			idev->msg->addr,
+			readl(idev->base + MST_RX_BYTES_XFRD),
+			readl(idev->base + MST_RX_XFER),
+			readl(idev->base + MST_TX_BYTES_XFRD),
+			readl(idev->base + MST_TX_XFER));
+		complete(&idev->msg_complete);
+	}
+
+out:
+	/* Clear interrupt */
+	writel(INT_MST, idev->base + INTERRUPT_STATUS);
+
+	return IRQ_HANDLED;
+}
+
+static int axxia_i2c_xfer_msg(struct axxia_i2c_dev *idev, struct i2c_msg *msg)
+{
+	u32 int_mask = MST_STATUS_ERR | MST_STATUS_SNS;
+	u32 rx_xfer, tx_xfer;
+	u32 addr_1, addr_2;
+	int ret;
+
+	if (msg->len > 255) {
+		dev_warn(idev->dev, "unsupported length %u\n", msg->len);
+		return -EINVAL;
+	}
+
+	idev->msg = msg;
+	idev->msg_xfrd = 0;
+	idev->msg_err = 0;
+	reinit_completion(&idev->msg_complete);
+
+	if (i2c_m_ten(msg)) {
+		/* 10-bit address
+		 *   addr_1: 5'b11110 | addr[9:8] | (R/nW)
+		 *   addr_2: addr[7:0]
+		 */
+		addr_1 = 0xF0 | ((msg->addr >> 7) & 0x06);
+		addr_2 = msg->addr & 0xFF;
+	} else {
+		/* 7-bit address
+		 *   addr_1: addr[6:0] | (R/nW)
+		 *   addr_2: dont care
+		 */
+		addr_1 = (msg->addr << 1) & 0xFF;
+		addr_2 = 0;
+	}
+
+	if (i2c_m_rd(msg)) {
+		/* I2C read transfer */
+		rx_xfer = i2c_m_recv_len(msg) ? I2C_SMBUS_BLOCK_MAX : msg->len;
+		tx_xfer = 0;
+		addr_1 |= 1;	/* Set the R/nW bit of the address */
+	} else {
+		/* I2C write transfer */
+		rx_xfer = 0;
+		tx_xfer = msg->len;
+	}
+
+	writel(rx_xfer, idev->base + MST_RX_XFER);
+	writel(tx_xfer, idev->base + MST_TX_XFER);
+	writel(addr_1, idev->base + MST_ADDR_1);
+	writel(addr_2, idev->base + MST_ADDR_2);
+
+	if (i2c_m_rd(msg))
+		int_mask |= MST_STATUS_RFL;
+	else if (axxia_i2c_fill_tx_fifo(idev) != 0)
+		int_mask |= MST_STATUS_TFL;
+
+	/* Start manual mode */
+	writel(CMD_MANUAL, idev->base + MST_COMMAND);
+
+	i2c_int_enable(idev, int_mask);
+
+	ret = wait_for_completion_timeout(&idev->msg_complete,
+					  I2C_XFER_TIMEOUT);
+
+	i2c_int_disable(idev, int_mask);
+
+	if (readl(idev->base + MST_COMMAND) & CMD_BUSY)
+		dev_warn(idev->dev, "busy after xfer\n");
+
+	if (ret == 0)
+		idev->msg_err = -ETIMEDOUT;
+
+	if (unlikely(idev->msg_err) && idev->msg_err != -ENXIO)
+		axxia_i2c_init(idev);
+
+	return idev->msg_err;
+}
+
+static int axxia_i2c_stop(struct axxia_i2c_dev *idev)
+{
+	u32 int_mask = MST_STATUS_ERR | MST_STATUS_SCC;
+	int ret;
+
+	reinit_completion(&idev->msg_complete);
+
+	/* Issue stop */
+	writel(0xb, idev->base + MST_COMMAND);
+	i2c_int_enable(idev, int_mask);
+	ret = wait_for_completion_timeout(&idev->msg_complete,
+					  I2C_STOP_TIMEOUT);
+	i2c_int_disable(idev, int_mask);
+	if (ret == 0)
+		return -ETIMEDOUT;
+
+	if (readl(idev->base + MST_COMMAND) & CMD_BUSY)
+		dev_warn(idev->dev, "busy after stop\n");
+
+	return 0;
+}
+
+static int
+axxia_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
+{
+	struct axxia_i2c_dev *idev = i2c_get_adapdata(adap);
+	int i;
+	int ret = 0;
+
+	for (i = 0; ret == 0 && i < num; ++i)
+		ret = axxia_i2c_xfer_msg(idev, &msgs[i]);
+
+	axxia_i2c_stop(idev);
+
+	return ret ? : i;
+}
+
+static u32 axxia_i2c_func(struct i2c_adapter *adap)
+{
+	u32 caps = (I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR |
+		    I2C_FUNC_SMBUS_EMUL | I2C_FUNC_SMBUS_BLOCK_DATA);
+	return caps;
+}
+
+static const struct i2c_algorithm axxia_i2c_algo = {
+	.master_xfer = axxia_i2c_xfer,
+	.functionality = axxia_i2c_func,
+};
+
+static int axxia_i2c_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct axxia_i2c_dev *idev = NULL;
+	struct resource *res;
+	void __iomem *base;
+	int irq;
+	int ret = 0;
+
+	idev = devm_kzalloc(&pdev->dev, sizeof(*idev), GFP_KERNEL);
+	if (!idev)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "missing interrupt resource\n");
+		return irq;
+	}
+
+	idev->i2c_clk = devm_clk_get(&pdev->dev, "i2c");
+	if (IS_ERR(idev->i2c_clk)) {
+		dev_err(&pdev->dev, "missing clock\n");
+		return PTR_ERR(idev->i2c_clk);
+	}
+
+	idev->base = base;
+	idev->dev = &pdev->dev;
+	init_completion(&idev->msg_complete);
+
+	of_property_read_u32(np, "clock-frequency", &idev->bus_clk_rate);
+	if (idev->bus_clk_rate == 0)
+		idev->bus_clk_rate = 100000;	/* default clock rate */
+
+	ret = axxia_i2c_init(idev);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to initialize\n");
+		return ret;
+	}
+
+	ret = devm_request_irq(&pdev->dev, irq, axxia_i2c_isr, 0,
+			       pdev->name, idev);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to claim IRQ%d\n", irq);
+		return ret;
+	}
+
+	clk_prepare_enable(idev->i2c_clk);
+
+	i2c_set_adapdata(&idev->adapter, idev);
+	strlcpy(idev->adapter.name, pdev->name, sizeof(idev->adapter.name));
+	idev->adapter.owner = THIS_MODULE;
+	idev->adapter.algo = &axxia_i2c_algo;
+	idev->adapter.dev.parent = &pdev->dev;
+	idev->adapter.dev.of_node = pdev->dev.of_node;
+
+	platform_set_drvdata(pdev, idev);
+
+	ret = i2c_add_adapter(&idev->adapter);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to add adapter\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int axxia_i2c_remove(struct platform_device *pdev)
+{
+	struct axxia_i2c_dev *idev = platform_get_drvdata(pdev);
+
+	clk_disable_unprepare(idev->i2c_clk);
+	i2c_del_adapter(&idev->adapter);
+
+	return 0;
+}
+
+/* Match table for of_platform binding */
+static const struct of_device_id axxia_i2c_of_match[] = {
+	{ .compatible = "lsi,api2c", },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, axxia_i2c_of_match);
+
+static struct platform_driver axxia_i2c_driver = {
+	.probe = axxia_i2c_probe,
+	.remove = axxia_i2c_remove,
+	.driver = {
+		.name = "axxia-i2c",
+		.of_match_table = axxia_i2c_of_match,
+	},
+};
+
+module_platform_driver(axxia_i2c_driver);
+
+MODULE_DESCRIPTION("Axxia I2C Bus driver");
+MODULE_AUTHOR("Anders Berg <[e-mail]>");
+MODULE_LICENSE("GPL v2");