[PATCH] i2c: Add support for DesignWare controllers

[Andrey Smirnov <andrew.smirnov@gmail.com>]

Add a driver for DesignWare I2C controller IP block found on several
SoCs including Altera SoC products

Tested using Terrasic SoCKit board and GPIO expander board with I2C
EEPROM on it

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---
 drivers/i2c/busses/Kconfig          |   6 +
 drivers/i2c/busses/Makefile         |   1 +
 drivers/i2c/busses/i2c-designware.c | 576 ++++++++++++++++++++++++++++++++++++
 3 files changed, 583 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-designware.c

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 181321b..a25a871 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -25,6 +25,12 @@ config I2C_IMX
 	  for many i.MX ARM based SoCs, for MPC85xx and MPC5200 PowerPC based
 	  SoCs.

+config I2C_DESIGNWARE
+	bool "Synopsys DesignWare I2C Master driver"
+	help
+	  If you say yes to this option, support will be included for the
+	  Synopsys DesignWare I2C adapter. Only master mode is supported.
+
 config I2C_MV64XXX
 	bool "Marvell mv64xxx I2C Controller"
 	depends on HAVE_CLK && OFDEVICE
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 1dbfbdf..8dccc38 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -5,3 +5,4 @@ obj-$(CONFIG_I2C_MV64XXX)	+= i2c-mv64xxx.o
 obj-$(CONFIG_I2C_OMAP)		+= i2c-omap.o
 obj-$(CONFIG_I2C_TEGRA)		+= i2c-tegra.o
 obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o
+obj-$(CONFIG_I2C_DESIGNWARE)	+= i2c-designware.o
diff --git a/drivers/i2c/busses/i2c-designware.c b/drivers/i2c/busses/i2c-designware.c
new file mode 100644
index 0000000..333d312
--- /dev/null
+++ b/drivers/i2c/busses/i2c-designware.c
@@ -0,0 +1,576 @@
+/*
+ * Synopsys DesignWare I2C adapter driver (master only).
+ *
+ * Partly based on code of similar driver from U-Boot:
+ *    Copyright (C) 2009 ST Micoelectronics
+ *
+ * and corresponding code from Linux Kernel
+ *    Copyright (C) 2006 Texas Instruments.
+ *    Copyright (C) 2007 MontaVista Software Inc.
+ *    Copyright (C) 2009 Provigent Ltd.
+ *
+ * Copyright (C) 2014 Andrey Smirnov <andrew.smirnov@gmail.com>
+ *
+ * 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 <clock.h>
+#include <common.h>
+#include <driver.h>
+#include <init.h>
+#include <of.h>
+#include <malloc.h>
+#include <types.h>
+#include <xfuncs.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+
+#include <io.h>
+#include <i2c/i2c.h>
+
+#define DW_I2C_BIT_RATE			100000
+
+#define DW_IC_CON			0x0
+#define DW_IC_CON_MASTER		(1 << 0)
+#define DW_IC_CON_SPEED_STD		(1 << 1)
+#define DW_IC_CON_SPEED_FAST		(1 << 2)
+#define DW_IC_CON_SLAVE_DISABLE		(1 << 6)
+
+#define DW_IC_TAR			0x4
+
+#define DW_IC_DATA_CMD			0x10
+#define DW_IC_DATA_CMD_CMD		(1 << 8)
+#define DW_IC_DATA_CMD_STOP		(1 << 9)
+
+#define DW_IC_SS_SCL_HCNT		0x14
+#define DW_IC_SS_SCL_LCNT		0x18
+#define DW_IC_FS_SCL_HCNT		0x1c
+#define DW_IC_FS_SCL_LCNT		0x20
+
+#define DW_IC_INTR_MASK			0x30
+
+#define DW_IC_RAW_INTR_STAT		0x34
+#define DW_IC_INTR_RX_UNDER		(1 << 0)
+#define DW_IC_INTR_RX_OVER		(1 << 1)
+#define DW_IC_INTR_RX_FULL		(1 << 2)
+#define DW_IC_INTR_TX_OVER		(1 << 3)
+#define DW_IC_INTR_TX_EMPTY		(1 << 4)
+#define DW_IC_INTR_RD_REQ		(1 << 5)
+#define DW_IC_INTR_TX_ABRT		(1 << 6)
+#define DW_IC_INTR_RX_DONE		(1 << 7)
+#define DW_IC_INTR_ACTIVITY		(1 << 8)
+#define DW_IC_INTR_STOP_DET		(1 << 9)
+#define DW_IC_INTR_START_DET		(1 << 10)
+#define DW_IC_INTR_GEN_CALL		(1 << 11)
+
+#define DW_IC_RX_TL			0x38
+#define DW_IC_TX_TL			0x3c
+#define DW_IC_CLR_INTR			0x40
+#define DW_IC_CLR_TX_ABRT		0x54
+
+#define DW_IC_ENABLE			0x6c
+#define DW_IC_ENABLE_ENABLE		(1 << 0)
+
+#define DW_IC_STATUS			0x70
+#define DW_IC_STATUS_TFNF		(1 << 1)
+#define DW_IC_STATUS_TFE		(1 << 2)
+#define DW_IC_STATUS_RFNE		(1 << 3)
+#define DW_IC_STATUS_MST_ACTIVITY	(1 << 5)
+
+#define DW_IC_TX_ABRT_SOURCE		0x80
+
+#define DW_IC_ENABLE_STATUS		0x9c
+#define DW_IC_ENABLE_STATUS_IC_EN	(1 << 0)
+
+#define DW_IC_COMP_TYPE			0xfc
+#define DW_IC_COMP_TYPE_VALUE		0x44570140
+
+#define MAX_T_POLL_COUNT		100
+
+#define DW_TIMEOUT_IDLE			(40 * MSECOND)
+#define DW_TIMEOUT_TX			(2 * MSECOND)
+#define DW_TIMEOUT_RX			(2 * MSECOND)
+
+struct dw_i2c_dev {
+	void __iomem *base;
+	struct clk *clk;
+	struct i2c_adapter adapter;
+};
+
+static inline struct dw_i2c_dev *to_dw_i2c_dev(struct i2c_adapter *a)
+{
+	return container_of(a, struct dw_i2c_dev, adapter);
+}
+
+static void i2c_dw_enable(struct dw_i2c_dev *dw, bool enable)
+{
+	/*
+	 * This subrotine is an implementation of an algorithm
+	 * described in "Cyclone V Hard Processor System Technical
+	 * Reference * Manual" p. 20-19, "Disabling the I2C Controller"
+	 */
+	int timeout = MAX_T_POLL_COUNT;
+
+	enable = enable ? DW_IC_ENABLE_ENABLE : 0;
+
+	do {
+		uint32_t ic_enable_status;
+
+		writel(enable, dw->base + DW_IC_ENABLE);
+
+		ic_enable_status = readl(dw->base + DW_IC_ENABLE_STATUS);
+		if ((ic_enable_status & DW_IC_ENABLE_STATUS_IC_EN) == enable)
+			return;
+
+		udelay(250);
+	} while (timeout--);
+
+	dev_warn(&dw->adapter.dev, "timeout in %sabling adapter\n",
+		 enable ? "en" : "dis");
+}
+
+/*
+ * All of the code pertaining to tming calculation is taken from
+ * analogous driver in Linux kernel
+ */
+static uint32_t
+i2c_dw_scl_hcnt(uint32_t ic_clk, uint32_t tSYMBOL, uint32_t tf, int cond,
+		int offset)
+{
+	/*
+	 * DesignWare I2C core doesn't seem to have solid strategy to meet
+	 * the tHD;STA timing spec.  Configuring _HCNT based on tHIGH spec
+	 * will result in violation of the tHD;STA spec.
+	 */
+	if (cond)
+		/*
+		 * Conditional expression:
+		 *
+		 *   IC_[FS]S_SCL_HCNT + (1+4+3) >= IC_CLK * tHIGH
+		 *
+		 * This is based on the DW manuals, and represents an ideal
+		 * configuration.  The resulting I2C bus speed will be
+		 * faster than any of the others.
+		 *
+		 * If your hardware is free from tHD;STA issue, try this one.
+		 */
+		return (ic_clk * tSYMBOL + 500000) / 1000000 - 8 + offset;
+	else
+		/*
+		 * Conditional expression:
+		 *
+		 *   IC_[FS]S_SCL_HCNT + 3 >= IC_CLK * (tHD;STA + tf)
+		 *
+		 * This is just experimental rule; the tHD;STA period turned
+		 * out to be proportinal to (_HCNT + 3).  With this setting,
+		 * we could meet both tHIGH and tHD;STA timing specs.
+		 *
+		 * If unsure, you'd better to take this alternative.
+		 *
+		 * The reason why we need to take into account "tf" here,
+		 * is the same as described in i2c_dw_scl_lcnt().
+		 */
+		return (ic_clk * (tSYMBOL + tf) + 500000) / 1000000
+			- 3 + offset;
+}
+
+static uint32_t
+i2c_dw_scl_lcnt(uint32_t ic_clk, uint32_t tLOW, uint32_t tf, int offset)
+{
+	/*
+	 * Conditional expression:
+	 *
+	 *   IC_[FS]S_SCL_LCNT + 1 >= IC_CLK * (tLOW + tf)
+	 *
+	 * DW I2C core starts counting the SCL CNTs for the LOW period
+	 * of the SCL clock (tLOW) as soon as it pulls the SCL line.
+	 * In order to meet the tLOW timing spec, we need to take into
+	 * account the fall time of SCL signal (tf).  Default tf value
+	 * should be 0.3 us, for safety.
+	 */
+	return ((ic_clk * (tLOW + tf) + 500000) / 1000000) - 1 + offset;
+}
+
+static void i2c_dw_setup_timings(struct dw_i2c_dev *dw)
+{
+	uint32_t hcnt, lcnt;
+
+	const uint32_t sda_falling_time = 300; /* ns */
+	const uint32_t scl_falling_time = 300; /* ns */
+
+	const unsigned int input_clock_khz = clk_get_rate(dw->clk) / 1000;
+
+	/* Set SCL timing parameters for standard-mode */
+	hcnt = i2c_dw_scl_hcnt(input_clock_khz,
+			       4000,	/* tHD;STA = tHIGH = 4.0 us */
+			       sda_falling_time,
+			       0,	/* 0: DW default, 1: Ideal */
+			       0);	/* No offset */
+	lcnt = i2c_dw_scl_lcnt(input_clock_khz,
+			       4700,	/* tLOW = 4.7 us */
+			       scl_falling_time,
+			       0);	/* No offset */
+
+	writel(hcnt, dw->base + DW_IC_SS_SCL_HCNT);
+	writel(lcnt, dw->base + DW_IC_SS_SCL_LCNT);
+
+	hcnt = i2c_dw_scl_hcnt(input_clock_khz,
+			       600,	/* tHD;STA = tHIGH = 0.6 us */
+			       sda_falling_time,
+			       0,	/* 0: DW default, 1: Ideal */
+			       0);	/* No offset */
+	lcnt = i2c_dw_scl_lcnt(input_clock_khz,
+			       1300,	/* tLOW = 1.3 us */
+			       scl_falling_time,
+			       0);	/* No offset */
+
+	writel(hcnt, dw->base + DW_IC_FS_SCL_HCNT);
+	writel(lcnt, dw->base + DW_IC_FS_SCL_LCNT);
+}
+
+static int i2c_dw_wait_for_bits(struct dw_i2c_dev *dw, uint32_t offset,
+				uint32_t mask, uint32_t value, uint64_t timeout)
+{
+	const uint64_t start = get_time_ns();
+
+	do {
+		const uint32_t reg = readl(dw->base + offset);
+
+		if ((reg & mask) == value)
+			return 0;
+
+	} while (!is_timeout(start, timeout));
+
+	return -ETIMEDOUT;
+}
+
+static int i2c_dw_wait_for_idle(struct dw_i2c_dev *dw)
+{
+	const uint32_t mask  = DW_IC_STATUS_MST_ACTIVITY | DW_IC_STATUS_TFE;
+	const uint32_t value = DW_IC_STATUS_TFE;
+
+	return i2c_dw_wait_for_bits(dw, DW_IC_STATUS, mask, value,
+				    DW_TIMEOUT_IDLE);
+}
+
+static int i2c_dw_wait_for_tx_fifo_not_full(struct dw_i2c_dev *dw)
+{
+	const uint32_t mask  = DW_IC_STATUS_TFNF;
+	const uint32_t value = DW_IC_STATUS_TFNF;
+
+	return i2c_dw_wait_for_bits(dw, DW_IC_STATUS, mask, value,
+				    DW_TIMEOUT_TX);
+}
+
+static int i2c_dw_wait_for_rx_fifo_not_empty(struct dw_i2c_dev *dw)
+{
+	const uint32_t mask  = DW_IC_STATUS_RFNE;
+	const uint32_t value = DW_IC_STATUS_RFNE;
+
+	return i2c_dw_wait_for_bits(dw, DW_IC_STATUS, mask, value,
+				    DW_TIMEOUT_RX);
+}
+
+static void i2c_dw_reset(struct dw_i2c_dev *dw)
+{
+	i2c_dw_enable(dw, false);
+	i2c_dw_enable(dw, true);
+}
+
+static void i2c_dw_abort_tx(struct dw_i2c_dev *dw)
+{
+	i2c_dw_reset(dw);
+}
+
+static void i2c_dw_abort_rx(struct dw_i2c_dev *dw)
+{
+	i2c_dw_reset(dw);
+}
+
+static int i2c_dw_read(struct dw_i2c_dev *dw,
+		       const struct i2c_msg *msg)
+{
+	int i;
+	for (i = 0; i < msg->len; i++) {
+		int ret;
+		const bool last_byte = i == msg->len - 1;
+		uint32_t ic_cmd_data = DW_IC_DATA_CMD_CMD;
+
+		if (last_byte)
+			ic_cmd_data |= DW_IC_DATA_CMD_STOP;
+
+		writel(ic_cmd_data, dw->base + DW_IC_DATA_CMD);
+
+		ret = i2c_dw_wait_for_rx_fifo_not_empty(dw);
+		if (ret < 0) {
+			i2c_dw_abort_rx(dw);
+			return ret;
+		}
+
+		msg->buf[i] = (uint8_t)readl(dw->base + DW_IC_DATA_CMD);
+	}
+
+	return msg->len;
+}
+
+static int i2c_dw_write(struct dw_i2c_dev *dw,
+			const struct i2c_msg *msg)
+{
+	int i;
+	uint32_t ic_int_stat;
+
+	for (i = 0; i < msg->len; i++) {
+		int ret;
+		uint32_t ic_cmd_data;
+		const bool last_byte = i == msg->len - 1;
+
+		ic_int_stat = readl(dw->base + DW_IC_RAW_INTR_STAT);
+
+		if (ic_int_stat & DW_IC_INTR_TX_ABRT)
+			return -EIO;
+
+		ret = i2c_dw_wait_for_tx_fifo_not_full(dw);
+		if (ret < 0) {
+			i2c_dw_abort_tx(dw);
+			return ret;
+		}
+
+		ic_cmd_data = msg->buf[i];
+
+		if (last_byte)
+			ic_cmd_data |= DW_IC_DATA_CMD_STOP;
+
+		writel(ic_cmd_data, dw->base + DW_IC_DATA_CMD);
+	}
+
+	return msg->len;
+}
+
+static int i2c_dw_wait_for_stop(struct dw_i2c_dev *dw)
+{
+	const uint32_t mask  = DW_IC_INTR_STOP_DET;
+	const uint32_t value = DW_IC_INTR_STOP_DET;
+
+	return i2c_dw_wait_for_bits(dw, DW_IC_RAW_INTR_STAT, mask, value,
+				    DW_TIMEOUT_IDLE);
+}
+
+static int i2c_dw_finish_xfer(struct dw_i2c_dev *dw)
+{
+	int ret;
+	uint32_t ic_int_stat;
+
+	/*
+	 * We expect the controller to signal STOP condition on the
+	 * bus, so we are going to wait for that first.
+	 */
+	ret = i2c_dw_wait_for_stop(dw);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Now that we now that the stop condition has been signaled
+	 * we need to wait for controller to go into IDLE state to
+	 * make sure all of the possible error conditions on the bus
+	 * have been propagated to apporpriate status
+	 * registers. Experiment shows that not doing so often results
+	 * in false positive "successful" transfers
+	*/
+	ret = i2c_dw_wait_for_idle(dw);
+
+	if (ret >= 0) {
+		ic_int_stat = readl(dw->base + DW_IC_RAW_INTR_STAT);
+
+		if (ic_int_stat & DW_IC_INTR_TX_ABRT)
+			return -EIO;
+	}
+
+	return ret;
+}
+
+static int i2c_dw_set_address(struct dw_i2c_dev *dw, uint8_t address)
+{
+	int ret;
+	uint32_t ic_tar;
+	/*
+	 * As per "Cyclone V Hard Processor System Technical Reference
+	 * Manual" p. 20-19, we have to wait for controller to be in
+	 * idle state in order to be able to set the address
+	 * dynamically
+	 */
+	ret = i2c_dw_wait_for_idle(dw);
+	if (ret < 0)
+		return ret;
+
+	ic_tar = readl(dw->base + DW_IC_TAR);
+	ic_tar &= 0xfffffc00;
+
+	writel(ic_tar | address, dw->base + DW_IC_TAR);
+
+	return 0;
+}
+
+static int i2c_dw_xfer(struct i2c_adapter *adapter,
+		       struct i2c_msg *msgs, int num)
+{
+	int i, ret = 0;
+	struct dw_i2c_dev *dw = to_dw_i2c_dev(adapter);
+
+	for (i = 0; i < num; i++) {
+		if (msgs[i].flags & I2C_M_DATA_ONLY)
+			return -ENOTSUPP;
+
+		ret = i2c_dw_set_address(dw, msgs[i].addr);
+		if (ret < 0)
+			break;
+
+		if (msgs[i].flags & I2C_M_RD)
+			ret = i2c_dw_read(dw, &msgs[i]);
+		else
+			ret = i2c_dw_write(dw, &msgs[i]);
+
+		if (ret < 0)
+			break;
+
+		ret = i2c_dw_finish_xfer(dw);
+		if (ret < 0)
+			break;
+	}
+
+	if (ret == -EIO) {
+		/*
+		 * If we got -EIO it means that transfer was for some
+		 * reason aborted, so we should figure out the reason
+		 * and take steps to clear that condition
+		 */
+		const uint32_t ic_tx_abrt_source =
+			readl(dw->base + DW_IC_TX_ABRT_SOURCE);
+		dev_dbg(&dw->adapter.dev,
+			"<%s> ic_tx_abrt_source: 0x%04x\n",
+			__func__, ic_tx_abrt_source);
+		readl(dw->base + DW_IC_CLR_TX_ABRT);
+
+		return ret;
+	}
+
+	if (ret < 0) {
+		i2c_dw_reset(dw);
+		return ret;
+	}
+
+	return num;
+}
+
+
+static int i2c_dw_probe(struct device_d *pdev)
+{
+	struct dw_i2c_dev *dw;
+	struct i2c_platform_data *pdata;
+	int ret, bitrate;
+	uint32_t ic_con, ic_comp_type_value;
+
+	pdata = pdev->platform_data;
+
+	dw = kzalloc(sizeof(*dw), GFP_KERNEL);
+
+	if (IS_ENABLED(CONFIG_COMMON_CLK)) {
+		dw->clk = clk_get(pdev, NULL);
+		if (IS_ERR(dw->clk)) {
+			ret = PTR_ERR(dw->clk);
+			goto fail;
+		}
+	}
+
+	dw->adapter.master_xfer = i2c_dw_xfer;
+	dw->adapter.nr = pdev->id;
+	dw->adapter.dev.parent = pdev;
+	dw->adapter.dev.device_node = pdev->device_node;
+
+	dw->base = dev_request_mem_region(pdev, 0);
+	if (IS_ERR(dw->base)) {
+		ret = PTR_ERR(dw->base);
+		goto fail;
+	}
+
+	ic_comp_type_value = readl(dw->base + DW_IC_COMP_TYPE);
+	if (ic_comp_type_value != DW_IC_COMP_TYPE_VALUE) {
+		dev_err(pdev,
+			"unknown DesignWare IP block 0x%08x",
+			ic_comp_type_value);
+		ret = -ENODEV;
+		goto fail;
+	}
+
+	i2c_dw_enable(dw, false);
+
+	if (IS_ENABLED(CONFIG_COMMON_CLK))
+		i2c_dw_setup_timings(dw);
+
+	bitrate = (pdata && pdata->bitrate) ? pdata->bitrate : DW_I2C_BIT_RATE;
+
+	/*
+	 * We have to clear 'ic_10bitaddr_master' in 'ic_tar'
+	 * register, otherwise 'ic_10bitaddr_master' in 'ic_con'
+	 * wouldn't clear. We don't care about preserving the contents
+	 * of that register so we set it to zero.
+	 */
+	writel(0, dw->base + DW_IC_TAR);
+
+	switch (bitrate) {
+	case 400000:
+		ic_con = DW_IC_CON_SPEED_FAST;
+		break;
+	default:
+		dev_warn(pdev, "requested bitrate (%d) is not supported."
+			 " Falling back to 100kHz", bitrate);
+	case 100000:		/* FALLTHROUGH */
+		ic_con = DW_IC_CON_SPEED_STD;
+		break;
+	}
+
+	ic_con |= DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE;
+
+	writel(ic_con, dw->base + DW_IC_CON);
+
+	/*
+	 * Since we will be working in polling mode set both
+	 * thresholds to their minimum
+	 */
+	writel(0, dw->base + DW_IC_RX_TL);
+	writel(0, dw->base + DW_IC_TX_TL);
+
+	/* Disable and clear all interrrupts */
+	writel(0, dw->base + DW_IC_INTR_MASK);
+	readl(dw->base + DW_IC_CLR_INTR);
+
+	i2c_dw_enable(dw, true);
+
+	ret = i2c_add_numbered_adapter(&dw->adapter);
+fail:
+	if (ret < 0) {
+		dev_err(pdev, "registration failed\n");
+		kfree(dw);
+	}
+
+	return ret;
+}
+
+static __maybe_unused struct of_device_id i2c_dw_dt_ids[] = {
+	{ .compatible = "snps,designware-i2c", },
+	{ /* sentinel */ }
+};
+
+static struct driver_d i2c_dw_driver = {
+	.probe = i2c_dw_probe,
+	.name = "i2c-designware",
+	.of_compatible = DRV_OF_COMPAT(i2c_dw_dt_ids),
+};
+coredevice_platform_driver(i2c_dw_driver);
--
2.1.4

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