i2c: altera: Add Altera I2C Controller driver

Add driver support for the Altera I2C Controller. The I2C
controller is soft IP for use in FPGAs.

Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

3 files changed, 522 insertions, 0 deletions

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index edc0cfb6fc1a..47165d7d486e 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -336,6 +336,16 @@ config I2C_POWERMAC
 
 comment "I2C system bus drivers (mostly embedded / system-on-chip)"
 
+config I2C_ALTERA
+	tristate "Altera Soft IP I2C"
+	depends on (ARCH_SOCFPGA || NIOS2) && OF
+	help
+	  If you say yes to this option, support will be included for the
+	  Altera Soft IP I2C interfaces on SoCFPGA and Nios2 architectures.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-altera.
+
 config I2C_ASPEED
 	tristate "Aspeed I2C Controller"
 	depends on ARCH_ASPEED || COMPILE_TEST
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 562daf738048..a57812fd2179 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -30,6 +30,7 @@ obj-$(CONFIG_I2C_HYDRA)		+= i2c-hydra.o
 obj-$(CONFIG_I2C_POWERMAC)	+= i2c-powermac.o
 
 # Embedded system I2C/SMBus host controller drivers
+obj-$(CONFIG_I2C_ALTERA)	+= i2c-altera.o
 obj-$(CONFIG_I2C_ASPEED)	+= i2c-aspeed.o
 obj-$(CONFIG_I2C_AT91)		+= i2c-at91.o
 obj-$(CONFIG_I2C_AU1550)	+= i2c-au1550.o
diff --git a/drivers/i2c/busses/i2c-altera.c b/drivers/i2c/busses/i2c-altera.c
new file mode 100644
index 000000000000..f5e1941e65b5
--- /dev/null
+++ b/drivers/i2c/busses/i2c-altera.c
@@ -0,0 +1,511 @@
+/*
+ *  Copyright Intel Corporation (C) 2017.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * 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.
+ */
+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 */
+};
+
+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 <= 100000) {
+		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(div_u64(300 * clk_mhz, 1000), 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;
+
+	if (!idev->msg) {
+		dev_warn(idev->dev, "unexpected interrupt\n");
+		altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
+		return IRQ_HANDLED;
+	}
+	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");
+	}
+
+	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);
+
+	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);
+	}
+
+	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;
+	u32 val;
+
+	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);
+
+	val = device_property_read_u32(idev->dev, "fifo-size",
+				       &idev->fifo_size);
+	if (val) {
+		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;
+	}
+
+	val = device_property_read_u32(idev->dev, "clock-frequency",
+				       &idev->bus_clk_rate);
+	if (val) {
+		dev_err(&pdev->dev, "Default to 100kHz\n");
+		idev->bus_clk_rate = 100000;	/* default clock rate */
+	}
+
+	if (idev->bus_clk_rate > 400000) {
+		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");