drivers/i2c/busses/i2c-altera.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  Copyright Intel Corporation (C) 2017.
  *
  * Based on the i2c-axxia.c driver.
  */
 #include <linux/clk.h>
 #include <linux/clkdev.h>
 #include <linux/err.h>
 #include <linux/i2c.h>
 #include <linux/iopoll.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/platform_device.h>

 #define ALTR_I2C_TFR_CMD	0x00	/* Transfer Command register */
 #define     ALTR_I2C_TFR_CMD_STA	BIT(9)	/* send START before byte */
 #define     ALTR_I2C_TFR_CMD_STO	BIT(8)	/* send STOP after byte */
 #define     ALTR_I2C_TFR_CMD_RW_D	BIT(0)	/* Direction of transfer */
 #define ALTR_I2C_RX_DATA	0x04	/* RX data FIFO register */
 #define ALTR_I2C_CTRL		0x08	/* Control register */
 #define     ALTR_I2C_CTRL_RXT_SHFT	4	/* RX FIFO Threshold */
 #define     ALTR_I2C_CTRL_TCT_SHFT	2	/* TFER CMD FIFO Threshold */
 #define     ALTR_I2C_CTRL_BSPEED	BIT(1)	/* Bus Speed (1=Fast) */
 #define     ALTR_I2C_CTRL_EN	BIT(0)	/* Enable Core (1=Enable) */
 #define ALTR_I2C_ISER		0x0C	/* Interrupt Status Enable register */
 #define     ALTR_I2C_ISER_RXOF_EN	BIT(4)	/* Enable RX OVERFLOW IRQ */
 #define     ALTR_I2C_ISER_ARB_EN	BIT(3)	/* Enable ARB LOST IRQ */
 #define     ALTR_I2C_ISER_NACK_EN	BIT(2)	/* Enable NACK DET IRQ */
 #define     ALTR_I2C_ISER_RXRDY_EN	BIT(1)	/* Enable RX Ready IRQ */
 #define     ALTR_I2C_ISER_TXRDY_EN	BIT(0)	/* Enable TX Ready IRQ */
 #define ALTR_I2C_ISR		0x10	/* Interrupt Status register */
 #define     ALTR_I2C_ISR_RXOF		BIT(4)	/* RX OVERFLOW IRQ */
 #define     ALTR_I2C_ISR_ARB		BIT(3)	/* ARB LOST IRQ */
 #define     ALTR_I2C_ISR_NACK		BIT(2)	/* NACK DET IRQ */
 #define     ALTR_I2C_ISR_RXRDY		BIT(1)	/* RX Ready IRQ */
 #define     ALTR_I2C_ISR_TXRDY		BIT(0)	/* TX Ready IRQ */
 #define ALTR_I2C_STATUS		0x14	/* Status register */
 #define     ALTR_I2C_STAT_CORE		BIT(0)	/* Core Status (0=idle) */
 #define ALTR_I2C_TC_FIFO_LVL	0x18	/* Transfer FIFO LVL register */
 #define ALTR_I2C_RX_FIFO_LVL	0x1C	/* Receive FIFO LVL register */
 #define ALTR_I2C_SCL_LOW	0x20	/* SCL low count register */
 #define ALTR_I2C_SCL_HIGH	0x24	/* SCL high count register */
 #define ALTR_I2C_SDA_HOLD	0x28	/* SDA hold count register */

 #define ALTR_I2C_ALL_IRQ	(ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | \
 				 ALTR_I2C_ISR_NACK | ALTR_I2C_ISR_RXRDY | \
 				 ALTR_I2C_ISR_TXRDY)

 #define ALTR_I2C_THRESHOLD	0	/* IRQ Threshold at 1 element */
 #define ALTR_I2C_DFLT_FIFO_SZ	4
 #define ALTR_I2C_TIMEOUT	100000	/* 100ms */
 #define ALTR_I2C_XFER_TIMEOUT	(msecs_to_jiffies(250))

 /**
  * altr_i2c_dev - I2C device context
  * @base: pointer to register struct
  * @msg: pointer to current message
  * @msg_len: 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
  * @buf: ptr to msg buffer for easier use.
  * @fifo_size: size of the FIFO passed in.
  * @isr_mask: cached copy of local ISR enables.
  * @isr_status: cached copy of local ISR status.
  * @lock: spinlock for IRQ synchronization.
  * @isr_mutex: mutex for IRQ thread.
  */
 struct altr_i2c_dev {
 	void __iomem *base;
 	struct i2c_msg *msg;
 	size_t msg_len;
 	int msg_err;
 	struct completion msg_complete;
 	struct device *dev;
 	struct i2c_adapter adapter;
 	struct clk *i2c_clk;
 	u32 bus_clk_rate;
 	u8 *buf;
 	u32 fifo_size;
 	u32 isr_mask;
 	u32 isr_status;
 	spinlock_t lock;	/* IRQ synchronization */
 	struct mutex isr_mutex;
 };

 static void
 altr_i2c_int_enable(struct altr_i2c_dev *idev, u32 mask, bool enable)
 {
 	unsigned long flags;
 	u32 int_en;

 	spin_lock_irqsave(&idev->lock, flags);

 	int_en = readl(idev->base + ALTR_I2C_ISER);
 	if (enable)
 		idev->isr_mask = int_en | mask;
 	else
 		idev->isr_mask = int_en & ~mask;

 	writel(idev->isr_mask, idev->base + ALTR_I2C_ISER);

 	spin_unlock_irqrestore(&idev->lock, flags);
 }

 static void altr_i2c_int_clear(struct altr_i2c_dev *idev, u32 mask)
 {
 	u32 int_en = readl(idev->base + ALTR_I2C_ISR);

 	writel(int_en | mask, idev->base + ALTR_I2C_ISR);
 }

 static void altr_i2c_core_disable(struct altr_i2c_dev *idev)
 {
 	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);

 	writel(tmp & ~ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
 }

 static void altr_i2c_core_enable(struct altr_i2c_dev *idev)
 {
 	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);

 	writel(tmp | ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
 }

 static void altr_i2c_reset(struct altr_i2c_dev *idev)
 {
 	altr_i2c_core_disable(idev);
 	altr_i2c_core_enable(idev);
 }

 static inline void altr_i2c_stop(struct altr_i2c_dev *idev)
 {
 	writel(ALTR_I2C_TFR_CMD_STO, idev->base + ALTR_I2C_TFR_CMD);
 }

 static void altr_i2c_init(struct altr_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 tmp = (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_RXT_SHFT) |
 		  (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_TCT_SHFT);
 	u32 t_high, t_low;

 	if (idev->bus_clk_rate <= I2C_MAX_STANDARD_MODE_FREQ) {
 		tmp &= ~ALTR_I2C_CTRL_BSPEED;
 		/* Standard mode SCL 50/50 */
 		t_high = divisor * 1 / 2;
 		t_low = divisor * 1 / 2;
 	} else {
 		tmp |= ALTR_I2C_CTRL_BSPEED;
 		/* Fast mode SCL 33/66 */
 		t_high = divisor * 1 / 3;
 		t_low = divisor * 2 / 3;
 	}
 	writel(tmp, idev->base + ALTR_I2C_CTRL);

 	dev_dbg(idev->dev, "rate=%uHz per_clk=%uMHz -> ratio=1:%u\n",
 		idev->bus_clk_rate, clk_mhz, divisor);

 	/* Reset controller */
 	altr_i2c_reset(idev);

 	/* SCL High Time */
 	writel(t_high, idev->base + ALTR_I2C_SCL_HIGH);
 	/* SCL Low Time */
 	writel(t_low, idev->base + ALTR_I2C_SCL_LOW);
 	/* SDA Hold Time, 300ns */
 	writel(3 * clk_mhz / 10, idev->base + ALTR_I2C_SDA_HOLD);

 	/* Mask all master interrupt bits */
 	altr_i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
 }

 /**
  * altr_i2c_transfer - On the last byte to be transmitted, send
  * a Stop bit on the last byte.
  */
 static void altr_i2c_transfer(struct altr_i2c_dev *idev, u32 data)
 {
 	/* On the last byte to be transmitted, send STOP */
 	if (idev->msg_len == 1)
 		data |= ALTR_I2C_TFR_CMD_STO;
 	if (idev->msg_len > 0)
 		writel(data, idev->base + ALTR_I2C_TFR_CMD);
 }

 /**
  * altr_i2c_empty_rx_fifo - Fetch data from RX FIFO until end of
  * transfer. Send a Stop bit on the last byte.
  */
 static void altr_i2c_empty_rx_fifo(struct altr_i2c_dev *idev)
 {
 	size_t rx_fifo_avail = readl(idev->base + ALTR_I2C_RX_FIFO_LVL);
 	int bytes_to_transfer = min(rx_fifo_avail, idev->msg_len);

 	while (bytes_to_transfer-- > 0) {
 		*idev->buf++ = readl(idev->base + ALTR_I2C_RX_DATA);
 		idev->msg_len--;
 		altr_i2c_transfer(idev, 0);
 	}
 }

 /**
  * altr_i2c_fill_tx_fifo - Fill TX FIFO from current message buffer.
  * @return: Number of bytes left to transfer.
  */
 static int altr_i2c_fill_tx_fifo(struct altr_i2c_dev *idev)
 {
 	size_t tx_fifo_avail = idev->fifo_size - readl(idev->base +
 						       ALTR_I2C_TC_FIFO_LVL);
 	int bytes_to_transfer = min(tx_fifo_avail, idev->msg_len);
 	int ret = idev->msg_len - bytes_to_transfer;

 	while (bytes_to_transfer-- > 0) {
 		altr_i2c_transfer(idev, *idev->buf++);
 		idev->msg_len--;
 	}

 	return ret;
 }

 static irqreturn_t altr_i2c_isr_quick(int irq, void *_dev)
 {
 	struct altr_i2c_dev *idev = _dev;
 	irqreturn_t ret = IRQ_HANDLED;

 	/* Read IRQ status but only interested in Enabled IRQs. */
 	idev->isr_status = readl(idev->base + ALTR_I2C_ISR) & idev->isr_mask;
 	if (idev->isr_status)
 		ret = IRQ_WAKE_THREAD;

 	return ret;
 }

 static irqreturn_t altr_i2c_isr(int irq, void *_dev)
 {
 	int ret;
 	bool read, finish = false;
 	struct altr_i2c_dev *idev = _dev;
 	u32 status = idev->isr_status;

 	mutex_lock(&idev->isr_mutex);
 	if (!idev->msg) {
 		dev_warn(idev->dev, "unexpected interrupt\n");
 		altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
 		goto out;
 	}
 	read = (idev->msg->flags & I2C_M_RD) != 0;

 	/* handle Lost Arbitration */
 	if (unlikely(status & ALTR_I2C_ISR_ARB)) {
 		altr_i2c_int_clear(idev, ALTR_I2C_ISR_ARB);
 		idev->msg_err = -EAGAIN;
 		finish = true;
 	} else if (unlikely(status & ALTR_I2C_ISR_NACK)) {
 		dev_dbg(idev->dev, "Could not get ACK\n");
 		idev->msg_err = -ENXIO;
 		altr_i2c_int_clear(idev, ALTR_I2C_ISR_NACK);
 		altr_i2c_stop(idev);
 		finish = true;
 	} else if (read && unlikely(status & ALTR_I2C_ISR_RXOF)) {
 		/* handle RX FIFO Overflow */
 		altr_i2c_empty_rx_fifo(idev);
 		altr_i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
 		altr_i2c_stop(idev);
 		dev_err(idev->dev, "RX FIFO Overflow\n");
 		finish = true;
 	} else if (read && (status & ALTR_I2C_ISR_RXRDY)) {
 		/* RX FIFO needs service? */
 		altr_i2c_empty_rx_fifo(idev);
 		altr_i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
 		if (!idev->msg_len)
 			finish = true;
 	} else if (!read && (status & ALTR_I2C_ISR_TXRDY)) {
 		/* TX FIFO needs service? */
 		altr_i2c_int_clear(idev, ALTR_I2C_ISR_TXRDY);
 		if (idev->msg_len > 0)
 			altr_i2c_fill_tx_fifo(idev);
 		else
 			finish = true;
 	} else {
 		dev_warn(idev->dev, "Unexpected interrupt: 0x%x\n", status);
 		altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
 	}

 	if (finish) {
 		/* Wait for the Core to finish */
 		ret = readl_poll_timeout_atomic(idev->base + ALTR_I2C_STATUS,
 						status,
 						!(status & ALTR_I2C_STAT_CORE),
 						1, ALTR_I2C_TIMEOUT);
 		if (ret)
 			dev_err(idev->dev, "message timeout\n");
 		altr_i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
 		altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
 		complete(&idev->msg_complete);
 		dev_dbg(idev->dev, "Message Complete\n");
 	}
 out:
 	mutex_unlock(&idev->isr_mutex);

 	return IRQ_HANDLED;
 }

 static int altr_i2c_xfer_msg(struct altr_i2c_dev *idev, struct i2c_msg *msg)
 {
 	u32 imask = ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | ALTR_I2C_ISR_NACK;
 	unsigned long time_left;
 	u32 value;
 	u8 addr = i2c_8bit_addr_from_msg(msg);

 	mutex_lock(&idev->isr_mutex);
 	idev->msg = msg;
 	idev->msg_len = msg->len;
 	idev->buf = msg->buf;
 	idev->msg_err = 0;
 	reinit_completion(&idev->msg_complete);
 	altr_i2c_core_enable(idev);

 	/* Make sure RX FIFO is empty */
 	do {
 		readl(idev->base + ALTR_I2C_RX_DATA);
 	} while (readl(idev->base + ALTR_I2C_RX_FIFO_LVL));

 	writel(ALTR_I2C_TFR_CMD_STA | addr, idev->base + ALTR_I2C_TFR_CMD);

 	if ((msg->flags & I2C_M_RD) != 0) {
 		imask |= ALTR_I2C_ISER_RXOF_EN | ALTR_I2C_ISER_RXRDY_EN;
 		altr_i2c_int_enable(idev, imask, true);
 		/* write the first byte to start the RX */
 		altr_i2c_transfer(idev, 0);
 	} else {
 		imask |= ALTR_I2C_ISR_TXRDY;
 		altr_i2c_int_enable(idev, imask, true);
 		altr_i2c_fill_tx_fifo(idev);
 	}
 	mutex_unlock(&idev->isr_mutex);

 	time_left = wait_for_completion_timeout(&idev->msg_complete,
 						ALTR_I2C_XFER_TIMEOUT);
 	altr_i2c_int_enable(idev, imask, false);

 	value = readl(idev->base + ALTR_I2C_STATUS) & ALTR_I2C_STAT_CORE;
 	if (value)
 		dev_err(idev->dev, "Core Status not IDLE...\n");

 	if (time_left == 0) {
 		idev->msg_err = -ETIMEDOUT;
 		dev_dbg(idev->dev, "Transaction timed out.\n");
 	}

 	altr_i2c_core_disable(idev);

 	return idev->msg_err;
 }

 static int
 altr_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 {
 	struct altr_i2c_dev *idev = i2c_get_adapdata(adap);
 	int i, ret;

 	for (i = 0; i < num; i++) {
 		ret = altr_i2c_xfer_msg(idev, msgs++);
 		if (ret)
 			return ret;
 	}
 	return num;
 }

 static u32 altr_i2c_func(struct i2c_adapter *adap)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 }

 static const struct i2c_algorithm altr_i2c_algo = {
 	.master_xfer = altr_i2c_xfer,
 	.functionality = altr_i2c_func,
 };

 static int altr_i2c_probe(struct platform_device *pdev)
 {
 	struct altr_i2c_dev *idev = NULL;
 	struct resource *res;
 	int irq, ret;

 	idev = devm_kzalloc(&pdev->dev, sizeof(*idev), GFP_KERNEL);
 	if (!idev)
 		return -ENOMEM;

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	idev->base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(idev->base))
 		return PTR_ERR(idev->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, NULL);
 	if (IS_ERR(idev->i2c_clk)) {
 		dev_err(&pdev->dev, "missing clock\n");
 		return PTR_ERR(idev->i2c_clk);
 	}

 	idev->dev = &pdev->dev;
 	init_completion(&idev->msg_complete);
 	spin_lock_init(&idev->lock);
 	mutex_init(&idev->isr_mutex);

 	ret = device_property_read_u32(idev->dev, "fifo-size",
 				       &idev->fifo_size);
 	if (ret) {
 		dev_err(&pdev->dev, "FIFO size set to default of %d\n",
 			ALTR_I2C_DFLT_FIFO_SZ);
 		idev->fifo_size = ALTR_I2C_DFLT_FIFO_SZ;
 	}

 	ret = device_property_read_u32(idev->dev, "clock-frequency",
 				       &idev->bus_clk_rate);
 	if (ret) {
 		dev_err(&pdev->dev, "Default to 100kHz\n");
 		idev->bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ;	/* default clock rate */
 	}

 	if (idev->bus_clk_rate > I2C_MAX_FAST_MODE_FREQ) {
 		dev_err(&pdev->dev, "invalid clock-frequency %d\n",
 			idev->bus_clk_rate);
 		return -EINVAL;
 	}

 	ret = devm_request_threaded_irq(&pdev->dev, irq, altr_i2c_isr_quick,
 					altr_i2c_isr, IRQF_ONESHOT,
 					pdev->name, idev);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to claim IRQ %d\n", irq);
 		return ret;
 	}

 	ret = clk_prepare_enable(idev->i2c_clk);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to enable clock\n");
 		return ret;
 	}

 	altr_i2c_init(idev);

 	i2c_set_adapdata(&idev->adapter, idev);
 	strlcpy(idev->adapter.name, pdev->name, sizeof(idev->adapter.name));
 	idev->adapter.owner = THIS_MODULE;
 	idev->adapter.algo = &altr_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) {
 		clk_disable_unprepare(idev->i2c_clk);
 		return ret;
 	}
 	dev_info(&pdev->dev, "Altera SoftIP I2C Probe Complete\n");

 	return 0;
 }

 static int altr_i2c_remove(struct platform_device *pdev)
 {
 	struct altr_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 altr_i2c_of_match[] = {
 	{ .compatible = "altr,softip-i2c-v1.0" },
 	{},
 };
 MODULE_DEVICE_TABLE(of, altr_i2c_of_match);

 static struct platform_driver altr_i2c_driver = {
 	.probe = altr_i2c_probe,
 	.remove = altr_i2c_remove,
 	.driver = {
 		.name = "altera-i2c",
 		.of_match_table = altr_i2c_of_match,
 	},
 };

 module_platform_driver(altr_i2c_driver);

 MODULE_DESCRIPTION("Altera Soft IP I2C bus driver");
 MODULE_AUTHOR("Thor Thayer <thor.thayer@linux.intel.com>");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright Intel Corporation (C) 2017.
	*
	* Based on the i2c-axxia.c driver.
	*/
	#include <linux/clk.h>
	#include <linux/clkdev.h>
	#include <linux/err.h>
	#include <linux/i2c.h>
	#include <linux/iopoll.h>
	#include <linux/interrupt.h>
	#include <linux/module.h>
	#include <linux/io.h>
	#include <linux/kernel.h>
	#include <linux/platform_device.h>

	#define ALTR_I2C_TFR_CMD 0x00 /* Transfer Command register */
	#define ALTR_I2C_TFR_CMD_STA BIT(9) /* send START before byte */
	#define ALTR_I2C_TFR_CMD_STO BIT(8) /* send STOP after byte */
	#define ALTR_I2C_TFR_CMD_RW_D BIT(0) /* Direction of transfer */
	#define ALTR_I2C_RX_DATA 0x04 /* RX data FIFO register */
	#define ALTR_I2C_CTRL 0x08 /* Control register */
	#define ALTR_I2C_CTRL_RXT_SHFT 4 /* RX FIFO Threshold */
	#define ALTR_I2C_CTRL_TCT_SHFT 2 /* TFER CMD FIFO Threshold */
	#define ALTR_I2C_CTRL_BSPEED BIT(1) /* Bus Speed (1=Fast) */
	#define ALTR_I2C_CTRL_EN BIT(0) /* Enable Core (1=Enable) */
	#define ALTR_I2C_ISER 0x0C /* Interrupt Status Enable register */
	#define ALTR_I2C_ISER_RXOF_EN BIT(4) /* Enable RX OVERFLOW IRQ */
	#define ALTR_I2C_ISER_ARB_EN BIT(3) /* Enable ARB LOST IRQ */
	#define ALTR_I2C_ISER_NACK_EN BIT(2) /* Enable NACK DET IRQ */
	#define ALTR_I2C_ISER_RXRDY_EN BIT(1) /* Enable RX Ready IRQ */
	#define ALTR_I2C_ISER_TXRDY_EN BIT(0) /* Enable TX Ready IRQ */
	#define ALTR_I2C_ISR 0x10 /* Interrupt Status register */
	#define ALTR_I2C_ISR_RXOF BIT(4) /* RX OVERFLOW IRQ */
	#define ALTR_I2C_ISR_ARB BIT(3) /* ARB LOST IRQ */
	#define ALTR_I2C_ISR_NACK BIT(2) /* NACK DET IRQ */
	#define ALTR_I2C_ISR_RXRDY BIT(1) /* RX Ready IRQ */
	#define ALTR_I2C_ISR_TXRDY BIT(0) /* TX Ready IRQ */
	#define ALTR_I2C_STATUS 0x14 /* Status register */
	#define ALTR_I2C_STAT_CORE BIT(0) /* Core Status (0=idle) */
	#define ALTR_I2C_TC_FIFO_LVL 0x18 /* Transfer FIFO LVL register */
	#define ALTR_I2C_RX_FIFO_LVL 0x1C /* Receive FIFO LVL register */
	#define ALTR_I2C_SCL_LOW 0x20 /* SCL low count register */
	#define ALTR_I2C_SCL_HIGH 0x24 /* SCL high count register */
	#define ALTR_I2C_SDA_HOLD 0x28 /* SDA hold count register */

	#define ALTR_I2C_ALL_IRQ (ALTR_I2C_ISR_RXOF \| ALTR_I2C_ISR_ARB \| \
	ALTR_I2C_ISR_NACK \| ALTR_I2C_ISR_RXRDY \| \
	ALTR_I2C_ISR_TXRDY)

	#define ALTR_I2C_THRESHOLD 0 /* IRQ Threshold at 1 element */
	#define ALTR_I2C_DFLT_FIFO_SZ 4
	#define ALTR_I2C_TIMEOUT 100000 /* 100ms */
	#define ALTR_I2C_XFER_TIMEOUT (msecs_to_jiffies(250))

	/**
	* altr_i2c_dev - I2C device context
	* @base: pointer to register struct
	* @msg: pointer to current message
	* @msg_len: 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
	* @buf: ptr to msg buffer for easier use.
	* @fifo_size: size of the FIFO passed in.
	* @isr_mask: cached copy of local ISR enables.
	* @isr_status: cached copy of local ISR status.
	* @lock: spinlock for IRQ synchronization.
	* @isr_mutex: mutex for IRQ thread.
	*/
	struct altr_i2c_dev {
	void __iomem *base;
	struct i2c_msg *msg;
	size_t msg_len;
	int msg_err;
	struct completion msg_complete;
	struct device *dev;
	struct i2c_adapter adapter;
	struct clk *i2c_clk;
	u32 bus_clk_rate;
	u8 *buf;
	u32 fifo_size;
	u32 isr_mask;
	u32 isr_status;
	spinlock_t lock; /* IRQ synchronization */
	struct mutex isr_mutex;
	};

	static void
	altr_i2c_int_enable(struct altr_i2c_dev *idev, u32 mask, bool enable)
	{
	unsigned long flags;
	u32 int_en;

	spin_lock_irqsave(&idev->lock, flags);

	int_en = readl(idev->base + ALTR_I2C_ISER);
	if (enable)
	idev->isr_mask = int_en \| mask;
	else
	idev->isr_mask = int_en & ~mask;

	writel(idev->isr_mask, idev->base + ALTR_I2C_ISER);

	spin_unlock_irqrestore(&idev->lock, flags);
	}

	static void altr_i2c_int_clear(struct altr_i2c_dev *idev, u32 mask)
	{
	u32 int_en = readl(idev->base + ALTR_I2C_ISR);

	writel(int_en \| mask, idev->base + ALTR_I2C_ISR);
	}

	static void altr_i2c_core_disable(struct altr_i2c_dev *idev)
	{
	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);

	writel(tmp & ~ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
	}

	static void altr_i2c_core_enable(struct altr_i2c_dev *idev)
	{
	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);

	writel(tmp \| ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
	}

	static void altr_i2c_reset(struct altr_i2c_dev *idev)
	{
	altr_i2c_core_disable(idev);
	altr_i2c_core_enable(idev);
	}

	static inline void altr_i2c_stop(struct altr_i2c_dev *idev)
	{
	writel(ALTR_I2C_TFR_CMD_STO, idev->base + ALTR_I2C_TFR_CMD);
	}

	static void altr_i2c_init(struct altr_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 tmp = (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_RXT_SHFT) \|
	(ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_TCT_SHFT);
	u32 t_high, t_low;

	if (idev->bus_clk_rate <= I2C_MAX_STANDARD_MODE_FREQ) {
	tmp &= ~ALTR_I2C_CTRL_BSPEED;
	/* Standard mode SCL 50/50 */
	t_high = divisor * 1 / 2;
	t_low = divisor * 1 / 2;
	} else {
	tmp \|= ALTR_I2C_CTRL_BSPEED;
	/* Fast mode SCL 33/66 */
	t_high = divisor * 1 / 3;
	t_low = divisor * 2 / 3;
	}
	writel(tmp, idev->base + ALTR_I2C_CTRL);

	dev_dbg(idev->dev, "rate=%uHz per_clk=%uMHz -> ratio=1:%u\n",
	idev->bus_clk_rate, clk_mhz, divisor);

	/* Reset controller */
	altr_i2c_reset(idev);

	/* SCL High Time */
	writel(t_high, idev->base + ALTR_I2C_SCL_HIGH);
	/* SCL Low Time */
	writel(t_low, idev->base + ALTR_I2C_SCL_LOW);
	/* SDA Hold Time, 300ns */
	writel(3 * clk_mhz / 10, idev->base + ALTR_I2C_SDA_HOLD);

	/* Mask all master interrupt bits */
	altr_i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
	}

	/**
	* altr_i2c_transfer - On the last byte to be transmitted, send
	* a Stop bit on the last byte.
	*/
	static void altr_i2c_transfer(struct altr_i2c_dev *idev, u32 data)
	{
	/* On the last byte to be transmitted, send STOP */
	if (idev->msg_len == 1)
	data \|= ALTR_I2C_TFR_CMD_STO;
	if (idev->msg_len > 0)
	writel(data, idev->base + ALTR_I2C_TFR_CMD);
	}

	/**
	* altr_i2c_empty_rx_fifo - Fetch data from RX FIFO until end of
	* transfer. Send a Stop bit on the last byte.
	*/
	static void altr_i2c_empty_rx_fifo(struct altr_i2c_dev *idev)
	{
	size_t rx_fifo_avail = readl(idev->base + ALTR_I2C_RX_FIFO_LVL);
	int bytes_to_transfer = min(rx_fifo_avail, idev->msg_len);

	while (bytes_to_transfer-- > 0) {
	*idev->buf++ = readl(idev->base + ALTR_I2C_RX_DATA);
	idev->msg_len--;
	altr_i2c_transfer(idev, 0);
	}
	}

	/**
	* altr_i2c_fill_tx_fifo - Fill TX FIFO from current message buffer.
	* @return: Number of bytes left to transfer.
	*/
	static int altr_i2c_fill_tx_fifo(struct altr_i2c_dev *idev)
	{
	size_t tx_fifo_avail = idev->fifo_size - readl(idev->base +
	ALTR_I2C_TC_FIFO_LVL);
	int bytes_to_transfer = min(tx_fifo_avail, idev->msg_len);
	int ret = idev->msg_len - bytes_to_transfer;

	while (bytes_to_transfer-- > 0) {
	altr_i2c_transfer(idev, *idev->buf++);
	idev->msg_len--;
	}

	return ret;
	}

	static irqreturn_t altr_i2c_isr_quick(int irq, void *_dev)
	{
	struct altr_i2c_dev *idev = _dev;
	irqreturn_t ret = IRQ_HANDLED;

	/* Read IRQ status but only interested in Enabled IRQs. */
	idev->isr_status = readl(idev->base + ALTR_I2C_ISR) & idev->isr_mask;
	if (idev->isr_status)
	ret = IRQ_WAKE_THREAD;

	return ret;
	}

	static irqreturn_t altr_i2c_isr(int irq, void *_dev)
	{
	int ret;
	bool read, finish = false;
	struct altr_i2c_dev *idev = _dev;
	u32 status = idev->isr_status;

	mutex_lock(&idev->isr_mutex);
	if (!idev->msg) {
	dev_warn(idev->dev, "unexpected interrupt\n");
	altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
	goto out;
	}
	read = (idev->msg->flags & I2C_M_RD) != 0;

	/* handle Lost Arbitration */
	if (unlikely(status & ALTR_I2C_ISR_ARB)) {
	altr_i2c_int_clear(idev, ALTR_I2C_ISR_ARB);
	idev->msg_err = -EAGAIN;
	finish = true;
	} else if (unlikely(status & ALTR_I2C_ISR_NACK)) {
	dev_dbg(idev->dev, "Could not get ACK\n");
	idev->msg_err = -ENXIO;
	altr_i2c_int_clear(idev, ALTR_I2C_ISR_NACK);
	altr_i2c_stop(idev);
	finish = true;
	} else if (read && unlikely(status & ALTR_I2C_ISR_RXOF)) {
	/* handle RX FIFO Overflow */
	altr_i2c_empty_rx_fifo(idev);
	altr_i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
	altr_i2c_stop(idev);
	dev_err(idev->dev, "RX FIFO Overflow\n");
	finish = true;
	} else if (read && (status & ALTR_I2C_ISR_RXRDY)) {
	/* RX FIFO needs service? */
	altr_i2c_empty_rx_fifo(idev);
	altr_i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
	if (!idev->msg_len)
	finish = true;
	} else if (!read && (status & ALTR_I2C_ISR_TXRDY)) {
	/* TX FIFO needs service? */
	altr_i2c_int_clear(idev, ALTR_I2C_ISR_TXRDY);
	if (idev->msg_len > 0)
	altr_i2c_fill_tx_fifo(idev);
	else
	finish = true;
	} else {
	dev_warn(idev->dev, "Unexpected interrupt: 0x%x\n", status);
	altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
	}

	if (finish) {
	/* Wait for the Core to finish */
	ret = readl_poll_timeout_atomic(idev->base + ALTR_I2C_STATUS,
	status,
	!(status & ALTR_I2C_STAT_CORE),
	1, ALTR_I2C_TIMEOUT);
	if (ret)
	dev_err(idev->dev, "message timeout\n");
	altr_i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
	altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
	complete(&idev->msg_complete);
	dev_dbg(idev->dev, "Message Complete\n");
	}
	out:
	mutex_unlock(&idev->isr_mutex);

	return IRQ_HANDLED;
	}

	static int altr_i2c_xfer_msg(struct altr_i2c_dev idev, struct i2c_msg msg)
	{
	u32 imask = ALTR_I2C_ISR_RXOF \| ALTR_I2C_ISR_ARB \| ALTR_I2C_ISR_NACK;
	unsigned long time_left;
	u32 value;
	u8 addr = i2c_8bit_addr_from_msg(msg);

	mutex_lock(&idev->isr_mutex);
	idev->msg = msg;
	idev->msg_len = msg->len;
	idev->buf = msg->buf;
	idev->msg_err = 0;
	reinit_completion(&idev->msg_complete);
	altr_i2c_core_enable(idev);

	/* Make sure RX FIFO is empty */
	do {
	readl(idev->base + ALTR_I2C_RX_DATA);
	} while (readl(idev->base + ALTR_I2C_RX_FIFO_LVL));

	writel(ALTR_I2C_TFR_CMD_STA \| addr, idev->base + ALTR_I2C_TFR_CMD);

	if ((msg->flags & I2C_M_RD) != 0) {
	imask \|= ALTR_I2C_ISER_RXOF_EN \| ALTR_I2C_ISER_RXRDY_EN;
	altr_i2c_int_enable(idev, imask, true);
	/* write the first byte to start the RX */
	altr_i2c_transfer(idev, 0);
	} else {
	imask \|= ALTR_I2C_ISR_TXRDY;
	altr_i2c_int_enable(idev, imask, true);
	altr_i2c_fill_tx_fifo(idev);
	}
	mutex_unlock(&idev->isr_mutex);

	time_left = wait_for_completion_timeout(&idev->msg_complete,
	ALTR_I2C_XFER_TIMEOUT);
	altr_i2c_int_enable(idev, imask, false);

	value = readl(idev->base + ALTR_I2C_STATUS) & ALTR_I2C_STAT_CORE;
	if (value)
	dev_err(idev->dev, "Core Status not IDLE...\n");

	if (time_left == 0) {
	idev->msg_err = -ETIMEDOUT;
	dev_dbg(idev->dev, "Transaction timed out.\n");
	}

	altr_i2c_core_disable(idev);

	return idev->msg_err;
	}

	static int
	altr_i2c_xfer(struct i2c_adapter adap, struct i2c_msg msgs, int num)
	{
	struct altr_i2c_dev *idev = i2c_get_adapdata(adap);
	int i, ret;

	for (i = 0; i < num; i++) {
	ret = altr_i2c_xfer_msg(idev, msgs++);
	if (ret)
	return ret;
	}
	return num;
	}

	static u32 altr_i2c_func(struct i2c_adapter *adap)
	{
	return I2C_FUNC_I2C \| I2C_FUNC_SMBUS_EMUL;
	}

	static const struct i2c_algorithm altr_i2c_algo = {
	.master_xfer = altr_i2c_xfer,
	.functionality = altr_i2c_func,
	};

	static int altr_i2c_probe(struct platform_device *pdev)
	{
	struct altr_i2c_dev *idev = NULL;
	struct resource *res;
	int irq, ret;

	idev = devm_kzalloc(&pdev->dev, sizeof(*idev), GFP_KERNEL);
	if (!idev)
	return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	idev->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(idev->base))
	return PTR_ERR(idev->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, NULL);
	if (IS_ERR(idev->i2c_clk)) {
	dev_err(&pdev->dev, "missing clock\n");
	return PTR_ERR(idev->i2c_clk);
	}

	idev->dev = &pdev->dev;
	init_completion(&idev->msg_complete);
	spin_lock_init(&idev->lock);
	mutex_init(&idev->isr_mutex);

	ret = device_property_read_u32(idev->dev, "fifo-size",
	&idev->fifo_size);
	if (ret) {
	dev_err(&pdev->dev, "FIFO size set to default of %d\n",
	ALTR_I2C_DFLT_FIFO_SZ);
	idev->fifo_size = ALTR_I2C_DFLT_FIFO_SZ;
	}

	ret = device_property_read_u32(idev->dev, "clock-frequency",
	&idev->bus_clk_rate);
	if (ret) {
	dev_err(&pdev->dev, "Default to 100kHz\n");
	idev->bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ; /* default clock rate */
	}

	if (idev->bus_clk_rate > I2C_MAX_FAST_MODE_FREQ) {
	dev_err(&pdev->dev, "invalid clock-frequency %d\n",
	idev->bus_clk_rate);
	return -EINVAL;
	}

	ret = devm_request_threaded_irq(&pdev->dev, irq, altr_i2c_isr_quick,
	altr_i2c_isr, IRQF_ONESHOT,
	pdev->name, idev);
	if (ret) {
	dev_err(&pdev->dev, "failed to claim IRQ %d\n", irq);
	return ret;
	}

	ret = clk_prepare_enable(idev->i2c_clk);
	if (ret) {
	dev_err(&pdev->dev, "failed to enable clock\n");
	return ret;
	}

	altr_i2c_init(idev);

	i2c_set_adapdata(&idev->adapter, idev);
	strlcpy(idev->adapter.name, pdev->name, sizeof(idev->adapter.name));
	idev->adapter.owner = THIS_MODULE;
	idev->adapter.algo = &altr_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) {
	clk_disable_unprepare(idev->i2c_clk);
	return ret;
	}
	dev_info(&pdev->dev, "Altera SoftIP I2C Probe Complete\n");

	return 0;
	}

	static int altr_i2c_remove(struct platform_device *pdev)
	{
	struct altr_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 altr_i2c_of_match[] = {
	{ .compatible = "altr,softip-i2c-v1.0" },
	{},
	};
	MODULE_DEVICE_TABLE(of, altr_i2c_of_match);

	static struct platform_driver altr_i2c_driver = {
	.probe = altr_i2c_probe,
	.remove = altr_i2c_remove,
	.driver = {
	.name = "altera-i2c",
	.of_match_table = altr_i2c_of_match,
	},
	};

	module_platform_driver(altr_i2c_driver);

	MODULE_DESCRIPTION("Altera Soft IP I2C bus driver");
	MODULE_AUTHOR("Thor Thayer <thor.thayer@linux.intel.com>");
	MODULE_LICENSE("GPL v2");