i2c: rewrite mvtwsi, support orion5x and kirkwood

This rewrite of the mvtwsi driver is 25% smaller and much
faster and simpler than the previous code.

Signed-off-by: Albert Aribaud <albert.aribaud@free.fr>
Acked-by: Prafulla Wadaskar<prafulla@marvell.com>
Acked-by: Heiko Schocher<hs@denx.de>

1 files changed, 341 insertions, 409 deletions

diff --git a/drivers/i2c/mvtwsi.c b/drivers/i2c/mvtwsi.c
index a4409be115..16a536f2fe 100644
--- a/drivers/i2c/mvtwsi.c
+++ b/drivers/i2c/mvtwsi.c
@@ -1,11 +1,9 @@
 /*
- * Driver for the i2c controller on the Marvell line of host bridges
- * (e.g, gt642[46]0, mv643[46]0, mv644[46]0, Orion SoC family),
- * and Kirkwood family.
+ * Driver for the TWSI (i2c) controller found on the Marvell
+ * orion5x and kirkwood SoC families.
  *
- * Based on:
- * Author: Mark A. Greer <mgreer@mvista.com>
- * 2005 (c) MontaVista, Software, Inc.
+ * Author: Albert Aribaud <albert.aribaud@free.fr>
+ * Copyright (c) 2010 Albert Aribaud.
  *
  * See file CREDITS for list of people who contributed to this
  * project.
@@ -24,473 +22,407 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  * MA 02110-1301 USA
- *
- * ported from Linux to u-boot
- * (C) Copyright 2009
- * Heiko Schocher, DENX Software Engineering, hs@denx.de.
  */
+
 #include <common.h>
 #include <i2c.h>
-#include <asm/arch/kirkwood.h>
 #include <asm/errno.h>
 #include <asm/io.h>
 
-DECLARE_GLOBAL_DATA_PTR;
+/*
+ * include a file that will provide CONFIG_I2C_MVTWSI_BASE
+ * and possibly other settings
+ */
 
-static unsigned int i2c_bus_num __attribute__ ((section (".data"))) = 0;
-#if defined(CONFIG_I2C_MUX)
-static unsigned int i2c_bus_num_mux __attribute__ ((section ("data"))) = 0;
+#if defined(CONFIG_ORION5X)
+#include <asm/arch/orion5x.h>
+#elif defined(CONFIG_KIRKWOOD)
+#include <asm/arch/kirkwood.h>
+#else
+#error Driver mvtwsi not supported by SoC or board
 #endif
 
-/* Register defines */
-#define	KW_I2C_REG_SLAVE_ADDR			0x00
-#define	KW_I2C_REG_DATA				0x04
-#define	KW_I2C_REG_CONTROL			0x08
-#define	KW_I2C_REG_STATUS			0x0c
-#define	KW_I2C_REG_BAUD				0x0c
-#define	KW_I2C_REG_EXT_SLAVE_ADDR		0x10
-#define	KW_I2C_REG_SOFT_RESET			0x1c
-
-#define	KW_I2C_REG_CONTROL_ACK			0x00000004
-#define	KW_I2C_REG_CONTROL_IFLG			0x00000008
-#define	KW_I2C_REG_CONTROL_STOP			0x00000010
-#define	KW_I2C_REG_CONTROL_START		0x00000020
-#define	KW_I2C_REG_CONTROL_TWSIEN		0x00000040
-#define	KW_I2C_REG_CONTROL_INTEN		0x00000080
-
-/* Ctlr status values */
-#define	KW_I2C_STATUS_BUS_ERR			0x00
-#define	KW_I2C_STATUS_MAST_START		0x08
-#define	KW_I2C_STATUS_MAST_REPEAT_START		0x10
-#define	KW_I2C_STATUS_MAST_WR_ADDR_ACK		0x18
-#define	KW_I2C_STATUS_MAST_WR_ADDR_NO_ACK	0x20
-#define	KW_I2C_STATUS_MAST_WR_ACK		0x28
-#define	KW_I2C_STATUS_MAST_WR_NO_ACK		0x30
-#define	KW_I2C_STATUS_MAST_LOST_ARB		0x38
-#define	KW_I2C_STATUS_MAST_RD_ADDR_ACK		0x40
-#define	KW_I2C_STATUS_MAST_RD_ADDR_NO_ACK	0x48
-#define	KW_I2C_STATUS_MAST_RD_DATA_ACK		0x50
-#define	KW_I2C_STATUS_MAST_RD_DATA_NO_ACK	0x58
-#define	KW_I2C_STATUS_MAST_WR_ADDR_2_ACK	0xd0
-#define	KW_I2C_STATUS_MAST_WR_ADDR_2_NO_ACK	0xd8
-#define	KW_I2C_STATUS_MAST_RD_ADDR_2_ACK	0xe0
-#define	KW_I2C_STATUS_MAST_RD_ADDR_2_NO_ACK	0xe8
-#define	KW_I2C_STATUS_NO_STATUS			0xf8
-
-/* Driver states */
-enum {
-	KW_I2C_STATE_INVALID,
-	KW_I2C_STATE_IDLE,
-	KW_I2C_STATE_WAITING_FOR_START_COND,
-	KW_I2C_STATE_WAITING_FOR_ADDR_1_ACK,
-	KW_I2C_STATE_WAITING_FOR_ADDR_2_ACK,
-	KW_I2C_STATE_WAITING_FOR_SLAVE_ACK,
-	KW_I2C_STATE_WAITING_FOR_SLAVE_DATA,
-};
+/*
+ * TWSI register structure
+ */
 
-/* Driver actions */
-enum {
-	KW_I2C_ACTION_INVALID,
-	KW_I2C_ACTION_CONTINUE,
-	KW_I2C_ACTION_SEND_START,
-	KW_I2C_ACTION_SEND_ADDR_1,
-	KW_I2C_ACTION_SEND_ADDR_2,
-	KW_I2C_ACTION_SEND_DATA,
-	KW_I2C_ACTION_RCV_DATA,
-	KW_I2C_ACTION_RCV_DATA_STOP,
-	KW_I2C_ACTION_SEND_STOP,
+struct  mvtwsi_registers {
+	u32 slave_address;
+	u32 data;
+	u32 control;
+	union {
+		u32 status;	/* when reading */
+		u32 baudrate;	/* when writing */
+	};
+	u32 xtnd_slave_addr;
+	u32 reserved[2];
+	u32 soft_reset;
 };
 
-/* defines to get compatible with Linux driver */
-#define IRQ_NONE	0x0
-#define IRQ_HANDLED	0x01
+/*
+ * Control register fields
+ */
 
-#define I2C_M_TEN	0x01
-#define I2C_M_RD	0x02
-#define	I2C_M_REV_DIR_ADDR	0x04;
+#define	MVTWSI_CONTROL_ACK	0x00000004
+#define	MVTWSI_CONTROL_IFLG	0x00000008
+#define	MVTWSI_CONTROL_STOP	0x00000010
+#define	MVTWSI_CONTROL_START	0x00000020
+#define	MVTWSI_CONTROL_TWSIEN	0x00000040
+#define	MVTWSI_CONTROL_INTEN	0x00000080
 
-struct i2c_msg {
-	u32	addr;
-	u32	flags;
-	u8	*buf;
-	u32	len;
-};
+/*
+ * Status register values -- only those expected in normal master
+ * operation on non-10-bit-address devices; whatever status we don't
+ * expect in nominal conditions (bus errors, arbitration losses,
+ * missing ACKs...) we just pass back to the caller as an error
+ * code.
+ */
 
-struct kirkwood_i2c_data {
-	int			irq;
-	u32			state;
-	u32			action;
-	u32			aborting;
-	u32			cntl_bits;
-	void			*reg_base;
-	u32			reg_base_p;
-	u32			reg_size;
-	u32			addr1;
-	u32			addr2;
-	u32			bytes_left;
-	u32			byte_posn;
-	u32			block;
-	int			rc;
-	u32			freq_m;
-	u32			freq_n;
-	struct i2c_msg		*msg;
-};
+#define	MVTWSI_STATUS_START		0x08
+#define	MVTWSI_STATUS_REPEATED_START	0x10
+#define	MVTWSI_STATUS_ADDR_W_ACK	0x18
+#define	MVTWSI_STATUS_DATA_W_ACK	0x28
+#define	MVTWSI_STATUS_ADDR_R_ACK	0x40
+#define	MVTWSI_STATUS_ADDR_R_NAK	0x48
+#define	MVTWSI_STATUS_DATA_R_ACK	0x50
+#define	MVTWSI_STATUS_DATA_R_NAK	0x58
+#define	MVTWSI_STATUS_IDLE		0xF8
+
+/*
+ * The single instance of the controller we'll be dealing with
+ */
 
-static struct kirkwood_i2c_data __drv_data __attribute__ ((section (".data")));
-static struct kirkwood_i2c_data *drv_data = &__drv_data;
-static struct i2c_msg __i2c_msg __attribute__ ((section (".data")));
-static struct i2c_msg *kirkwood_i2c_msg = &__i2c_msg;
+static struct  mvtwsi_registers *twsi =
+	(struct  mvtwsi_registers *) CONFIG_I2C_MVTWSI_BASE;
 
 /*
- *****************************************************************************
- *
- *	Finite State Machine & Interrupt Routines
- *
- *****************************************************************************
+ * Returned statuses are 0 for success and nonzero otherwise.
+ * Currently, cmd_i2c and cmd_eeprom do not interpret an error status.
+ * Thus to ease debugging, the return status contains some debug info:
+ * - bits 31..24 are error class: 1 is timeout, 2 is 'status mismatch'.
+ * - bits 23..16 are the last value of the control register.
+ * - bits 15..8 are the last value of the status register.
+ * - bits 7..0 are the expected value of the status register.
  */
 
-static inline int abs(int n)
-{
-	 if(n >= 0)
-		return n;
-	else
-		return n * -1;
-}
+#define MVTWSI_ERROR_WRONG_STATUS	0x01
+#define MVTWSI_ERROR_TIMEOUT		0x02
 
-static void kirkwood_calculate_speed(int speed)
-{
-	int	calcspeed;
-	int	diff;
-	int	best_diff = CONFIG_SYS_TCLK;
-	int	best_speed = 0;
-	int	m, n;
-	int	tmp[8] = {2, 4, 8, 16, 32, 64, 128, 256};
+#define MVTWSI_ERROR(ec, lc, ls, es) (((ec << 24) & 0xFF000000) | \
+	((lc << 16) & 0x00FF0000) | ((ls<<8) & 0x0000FF00) | (es & 0xFF))
 
-	for (n = 0; n < 8; n++) {
-		for (m = 0; m < 16; m++) {
-			calcspeed = CONFIG_SYS_TCLK / (10 * (m + 1) * tmp[n]);
-			diff = abs((speed - calcspeed));
-			if ( diff < best_diff) {
-				best_diff = diff;
-				best_speed = calcspeed;
-				drv_data->freq_m = m;
-				drv_data->freq_n = n;
-			}
+/*
+ * Wait for IFLG to raise, or return 'timeout'; then if status is as expected,
+ * return 0 (ok) or return 'wrong status'.
+ */
+static int twsi_wait(int expected_status)
+{
+	int control, status;
+	int timeout = 1000;
+
+	do {
+		control = readl(&twsi->control);
+		if (control & MVTWSI_CONTROL_IFLG) {
+			status = readl(&twsi->status);
+			if (status == expected_status)
+				return 0;
+			else
+				return MVTWSI_ERROR(
+					MVTWSI_ERROR_WRONG_STATUS,
+					control, status, expected_status);
 		}
-	}
+		udelay(10); /* one clock cycle at 100 kHz */
+	} while (timeout--);
+	status = readl(&twsi->status);
+	return MVTWSI_ERROR(
+		MVTWSI_ERROR_TIMEOUT, control, status, expected_status);
 }
 
-/* Reset hardware and initialize FSM */
-static void
-kirkwood_i2c_hw_init(int speed, int slaveadd)
+/*
+ * These flags are ORed to any write to the control register
+ * They allow global setting of TWSIEN and ACK.
+ * By default none are set.
+ * twsi_start() sets TWSIEN (in case the controller was disabled)
+ * twsi_recv() sets ACK or resets it depending on expected status.
+ */
+static u8 twsi_control_flags = MVTWSI_CONTROL_TWSIEN;
+
+/*
+ * Assert the START condition, either in a single I2C transaction
+ * or inside back-to-back ones (repeated starts).
+ */
+static int twsi_start(int expected_status)
 {
-	drv_data->state = KW_I2C_STATE_IDLE;
-
-	kirkwood_calculate_speed(speed);
-	writel(0, CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_SOFT_RESET);
-	writel((((drv_data->freq_m & 0xf) << 3) | (drv_data->freq_n & 0x7)),
-		CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_BAUD);
-	writel(slaveadd, CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_SLAVE_ADDR);
-	writel(0, CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_EXT_SLAVE_ADDR);
-	writel(KW_I2C_REG_CONTROL_TWSIEN | KW_I2C_REG_CONTROL_STOP,
-		CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
+	/* globally set TWSIEN in case it was not */
+	twsi_control_flags |= MVTWSI_CONTROL_TWSIEN;
+	/* assert START */
+	writel(twsi_control_flags | MVTWSI_CONTROL_START, &twsi->control);
+	/* wait for controller to process START */
+	return twsi_wait(expected_status);
 }
 
-static void
-kirkwood_i2c_fsm(u32 status)
+/*
+ * Send a byte (i2c address or data).
+ */
+static int twsi_send(u8 byte, int expected_status)
 {
-	/*
-	 * If state is idle, then this is likely the remnants of an old
-	 * operation that driver has given up on or the user has killed.
-	 * If so, issue the stop condition and go to idle.
-	 */
-	if (drv_data->state == KW_I2C_STATE_IDLE) {
-		drv_data->action = KW_I2C_ACTION_SEND_STOP;
-		return;
-	}
-
-	/* The status from the ctlr [mostly] tells us what to do next */
-	switch (status) {
-	/* Start condition interrupt */
-	case KW_I2C_STATUS_MAST_START: /* 0x08 */
-	case KW_I2C_STATUS_MAST_REPEAT_START: /* 0x10 */
-		drv_data->action = KW_I2C_ACTION_SEND_ADDR_1;
-		drv_data->state = KW_I2C_STATE_WAITING_FOR_ADDR_1_ACK;
-		break;
-
-	/* Performing a write */
-	case KW_I2C_STATUS_MAST_WR_ADDR_ACK: /* 0x18 */
-		if (drv_data->msg->flags & I2C_M_TEN) {
-			drv_data->action = KW_I2C_ACTION_SEND_ADDR_2;
-			drv_data->state =
-				KW_I2C_STATE_WAITING_FOR_ADDR_2_ACK;
-			break;
-		}
-		/* FALLTHRU */
-	case KW_I2C_STATUS_MAST_WR_ADDR_2_ACK: /* 0xd0 */
-	case KW_I2C_STATUS_MAST_WR_ACK: /* 0x28 */
-		if ((drv_data->bytes_left == 0)
-				|| (drv_data->aborting
-					&& (drv_data->byte_posn != 0))) {
-			drv_data->action = KW_I2C_ACTION_SEND_STOP;
-			drv_data->state = KW_I2C_STATE_IDLE;
-		} else {
-			drv_data->action = KW_I2C_ACTION_SEND_DATA;
-			drv_data->state =
-				KW_I2C_STATE_WAITING_FOR_SLAVE_ACK;
-			drv_data->bytes_left--;
-		}
-		break;
-
-	/* Performing a read */
-	case KW_I2C_STATUS_MAST_RD_ADDR_ACK: /* 40 */
-		if (drv_data->msg->flags & I2C_M_TEN) {
-			drv_data->action = KW_I2C_ACTION_SEND_ADDR_2;
-			drv_data->state =
-				KW_I2C_STATE_WAITING_FOR_ADDR_2_ACK;
-			break;
-		}
-		/* FALLTHRU */
-	case KW_I2C_STATUS_MAST_RD_ADDR_2_ACK: /* 0xe0 */
-		if (drv_data->bytes_left == 0) {
-			drv_data->action = KW_I2C_ACTION_SEND_STOP;
-			drv_data->state = KW_I2C_STATE_IDLE;
-			break;
-		}
-		/* FALLTHRU */
-	case KW_I2C_STATUS_MAST_RD_DATA_ACK: /* 0x50 */
-		if (status != KW_I2C_STATUS_MAST_RD_DATA_ACK)
-			drv_data->action = KW_I2C_ACTION_CONTINUE;
-		else {
-			drv_data->action = KW_I2C_ACTION_RCV_DATA;
-			drv_data->bytes_left--;
-		}
-		drv_data->state = KW_I2C_STATE_WAITING_FOR_SLAVE_DATA;
-
-		if ((drv_data->bytes_left == 1) || drv_data->aborting)
-			drv_data->cntl_bits &= ~KW_I2C_REG_CONTROL_ACK;
-		break;
-
-	case KW_I2C_STATUS_MAST_RD_DATA_NO_ACK: /* 0x58 */
-		drv_data->action = KW_I2C_ACTION_RCV_DATA_STOP;
-		drv_data->state = KW_I2C_STATE_IDLE;
-		break;
-
-	case KW_I2C_STATUS_MAST_WR_ADDR_NO_ACK: /* 0x20 */
-	case KW_I2C_STATUS_MAST_WR_NO_ACK: /* 30 */
-	case KW_I2C_STATUS_MAST_RD_ADDR_NO_ACK: /* 48 */
-		/* Doesn't seem to be a device at other end */
-		drv_data->action = KW_I2C_ACTION_SEND_STOP;
-		drv_data->state = KW_I2C_STATE_IDLE;
-		drv_data->rc = -ENODEV;
-		break;
-
-	default:
-		printf("kirkwood_i2c_fsm: Ctlr Error -- state: 0x%x, "
-			"status: 0x%x, addr: 0x%x, flags: 0x%x\n",
-			 drv_data->state, status, drv_data->msg->addr,
-			 drv_data->msg->flags);
-		drv_data->action = KW_I2C_ACTION_SEND_STOP;
-		kirkwood_i2c_hw_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);
-		drv_data->rc = -EIO;
-	}
+	/* put byte in data register for sending */
+	writel(byte, &twsi->data);
+	/* clear any pending interrupt -- that'll cause sending */
+	writel(twsi_control_flags, &twsi->control);
+	/* wait for controller to receive byte and check ACK */
+	return twsi_wait(expected_status);
 }
 
-static void
-kirkwood_i2c_do_action(void)
+/*
+ * Receive a byte.
+ * Global mvtwsi_control_flags variable says if we should ack or nak.
+ */
+static int twsi_recv(u8 *byte)
 {
-	switch(drv_data->action) {
-	case KW_I2C_ACTION_CONTINUE:
-		writel(drv_data->cntl_bits,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-		break;
-
-	case KW_I2C_ACTION_SEND_START:
-		writel(drv_data->cntl_bits | KW_I2C_REG_CONTROL_START,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-		break;
-
-	case KW_I2C_ACTION_SEND_ADDR_1:
-		writel(drv_data->addr1,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_DATA);
-		writel(drv_data->cntl_bits,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-		break;
-
-	case KW_I2C_ACTION_SEND_ADDR_2:
-		writel(drv_data->addr2,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_DATA);
-		writel(drv_data->cntl_bits,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-		break;
-
-	case KW_I2C_ACTION_SEND_DATA:
-		writel(drv_data->msg->buf[drv_data->byte_posn++],
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_DATA);
-		writel(drv_data->cntl_bits,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-		break;
-
-	case KW_I2C_ACTION_RCV_DATA:
-		drv_data->msg->buf[drv_data->byte_posn++] =
-			readl(CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_DATA);
-		writel(drv_data->cntl_bits,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-		break;
-
-	case KW_I2C_ACTION_RCV_DATA_STOP:
-		drv_data->msg->buf[drv_data->byte_posn++] =
-			readl(CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_DATA);
-		drv_data->cntl_bits &= ~KW_I2C_REG_CONTROL_INTEN;
-		writel(drv_data->cntl_bits | KW_I2C_REG_CONTROL_STOP,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-		drv_data->block = 0;
-		break;
-
-	case KW_I2C_ACTION_INVALID:
-	default:
-		printf("kirkwood_i2c_do_action: Invalid action: %d\n",
-			drv_data->action);
-		drv_data->rc = -EIO;
-		/* FALLTHRU */
-	case KW_I2C_ACTION_SEND_STOP:
-		drv_data->cntl_bits &= ~KW_I2C_REG_CONTROL_INTEN;
-		writel(drv_data->cntl_bits | KW_I2C_REG_CONTROL_STOP,
-			CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-		drv_data->block = 0;
-		break;
-	}
+	int expected_status, status;
+
+	/* compute expected status based on ACK bit in global control flags */
+	if (twsi_control_flags & MVTWSI_CONTROL_ACK)
+		expected_status = MVTWSI_STATUS_DATA_R_ACK;
+	else
+		expected_status = MVTWSI_STATUS_DATA_R_NAK;
+	/* acknowledge *previous state* and launch receive */
+	writel(twsi_control_flags, &twsi->control);
+	/* wait for controller to receive byte and assert ACK or NAK */
+	status = twsi_wait(expected_status);
+	/* if we did receive expected byte then store it */
+	if (status == 0)
+		*byte = readl(&twsi->data);
+	/* return status */
+	return status;
 }
 
-static	int
-kirkwood_i2c_intr(void)
+/*
+ * Assert the STOP condition.
+ * This is also used to force the bus back in idle (SDA=SCL=1).
+ */
+static int twsi_stop(int status)
 {
-	u32		status;
-	u32		ctrl;
-	int		rc = IRQ_NONE;
-
-	ctrl = readl(CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-	while ((ctrl & KW_I2C_REG_CONTROL_IFLG) &&
-		(drv_data->rc == 0)) {
-		status = readl(CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_STATUS);
-		kirkwood_i2c_fsm(status);
-		kirkwood_i2c_do_action();
-		rc = IRQ_HANDLED;
-		ctrl = readl(CONFIG_I2C_KW_REG_BASE + KW_I2C_REG_CONTROL);
-		udelay(1000);
-	}
-	return rc;
+	int control, stop_status;
+	int timeout = 1000;
+
+	/* assert STOP */
+	control = MVTWSI_CONTROL_TWSIEN | MVTWSI_CONTROL_STOP;
+	writel(control, &twsi->control);
+	/* wait for IDLE; IFLG won't rise so twsi_wait() is no use. */
+	do {
+		stop_status = readl(&twsi->status);
+		if (stop_status == MVTWSI_STATUS_IDLE)
+			break;
+		udelay(10); /* one clock cycle at 100 kHz */
+	} while (timeout--);
+	control = readl(&twsi->control);
+	if (stop_status != MVTWSI_STATUS_IDLE)
+		if (status == 0)
+			status = MVTWSI_ERROR(
+				MVTWSI_ERROR_TIMEOUT,
+				control, status, MVTWSI_STATUS_IDLE);
+	return status;
 }
 
-static void
-kirkwood_i2c_doio(struct i2c_msg *msg)
-{
-	int	ret;
+/*
+ * Ugly formula to convert m and n values to a frequency comes from
+ * TWSI specifications
+ */
 
-	while ((drv_data->rc == 0) && (drv_data->state != KW_I2C_STATE_IDLE)) {
-		/* poll Status register */
-		ret = kirkwood_i2c_intr();
-		if (ret == IRQ_NONE)
-			udelay(10);
-	}
+#define TWSI_FREQUENCY(m, n) \
+	((u8) (CONFIG_SYS_TCLK / (10 * (m + 1) * 2 * (1 << n))))
+
+/*
+ * These are required to be reprogrammed before enabling the controller
+ * because a reset loses them.
+ * Default values come from the spec, but a twsi_reset will change them.
+ * twsi_slave_address left uninitialized lest checkpatch.pl complains.
+ */
+
+/* Baudrate generator: m (bits 7..4) =4, n (bits 3..0) =4 */
+static u8 twsi_baud_rate = 0x44; /* baudrate at controller reset */
+/* Default frequency corresponding to default m=4, n=4 */
+static u8 twsi_actual_speed = TWSI_FREQUENCY(4, 4);
+/* Default slave address is 0 (so is an uninitialized static) */
+static u8 twsi_slave_address;
+
+/*
+ * Reset controller.
+ * Called at end of i2c_init unsuccessful i2c transactions.
+ * Controller reset also resets the baud rate and slave address, so
+ * re-establish them.
+ */
+static void twsi_reset(void)
+{
+	/* ensure controller will be enabled by any twsi*() function */
+	twsi_control_flags = MVTWSI_CONTROL_TWSIEN;
+	/* reset controller */
+	writel(0, &twsi->soft_reset);
+	/* wait 2 ms -- this is what the Marvell LSP does */
+	udelay(20000);
+	/* set baud rate */
+	writel(twsi_baud_rate, &twsi->baudrate);
+	/* set slave address even though we don't use it */
+	writel(twsi_slave_address, &twsi->slave_address);
+	writel(0, &twsi->xtnd_slave_addr);
+	/* assert STOP but don't care for the result */
+	(void) twsi_stop(0);
 }
 
-static void
-kirkwood_i2c_prepare_for_io(struct i2c_msg *msg)
+/*
+ * I2C init called by cmd_i2c when doing 'i2c reset'.
+ * Sets baud to the highest possible value not exceeding requested one.
+ */
+void i2c_init(int requested_speed, int slaveadd)
 {
-	u32	dir = 0;
-
-	drv_data->msg = msg;
-	drv_data->byte_posn = 0;
-	drv_data->bytes_left = msg->len;
-	drv_data->aborting = 0;
-	drv_data->rc = 0;
-	/* in u-boot we use no IRQs */
-	drv_data->cntl_bits = KW_I2C_REG_CONTROL_ACK | KW_I2C_REG_CONTROL_TWSIEN;
-
-	if (msg->flags & I2C_M_RD)
-		dir = 1;
-	if (msg->flags & I2C_M_TEN) {
-		drv_data->addr1 = 0xf0 | (((u32)msg->addr & 0x300) >> 7) | dir;
-		drv_data->addr2 = (u32)msg->addr & 0xff;
-	} else {
-		drv_data->addr1 = ((u32)msg->addr & 0x7f) << 1 | dir;
-		drv_data->addr2 = 0;
+	int	tmp_speed, highest_speed, n, m;
+	int	baud = 0x44; /* baudrate at controller reset */
+
+	/* use actual speed to collect progressively higher values */
+	highest_speed = 0;
+	/* compute m, n setting for highest speed not above requested speed */
+	for (n = 0; n < 8; n++) {
+		for (m = 0; m < 16; m++) {
+			tmp_speed = TWSI_FREQUENCY(m, n);
+			if ((tmp_speed <= requested_speed)
+			 && (tmp_speed > highest_speed)) {
+				highest_speed = tmp_speed;
+				baud = (m << 3) | n;
+			}
+		}
 	}
-	/* OK, no start it (from kirkwood_i2c_execute_msg())*/
-	drv_data->action = KW_I2C_ACTION_SEND_START;
-	drv_data->state = KW_I2C_STATE_WAITING_FOR_START_COND;
-	drv_data->block = 1;
-	kirkwood_i2c_do_action();
+	/* save baud rate and slave for later calls to twsi_reset */
+	twsi_baud_rate = baud;
+	twsi_actual_speed = highest_speed;
+	twsi_slave_address = slaveadd;
+	/* reset controller */
+	twsi_reset();
 }
 
-void
-i2c_init(int speed, int slaveadd)
+/*
+ * Begin I2C transaction with expected start status, at given address.
+ * Common to i2c_probe, i2c_read and i2c_write.
+ * Expected address status will derive from direction bit (bit 0) in addr.
+ */
+static int i2c_begin(int expected_start_status, u8 addr)
 {
-	kirkwood_i2c_hw_init(speed, slaveadd);
+	int status, expected_addr_status;
+
+	/* compute expected address status from direction bit in addr */
+	if (addr & 1) /* reading */
+		expected_addr_status = MVTWSI_STATUS_ADDR_R_ACK;
+	else /* writing */
+		expected_addr_status = MVTWSI_STATUS_ADDR_W_ACK;
+	/* assert START */
+	status = twsi_start(expected_start_status);
+	/* send out the address if the start went well */
+	if (status == 0)
+		status = twsi_send(addr, expected_addr_status);
+	/* return ok or status of first failure to caller */
+	return status;
 }
 
-int
-i2c_read(u8 dev, uint addr, int alen, u8 *data, int length)
+/*
+ * I2C probe called by cmd_i2c when doing 'i2c probe'.
+ * Begin read, nak data byte, end.
+ */
+int i2c_probe(uchar chip)
 {
-	kirkwood_i2c_msg->buf = data;
-	kirkwood_i2c_msg->len = length;
-	kirkwood_i2c_msg->addr = dev;
-	kirkwood_i2c_msg->flags = I2C_M_RD;
-
-	kirkwood_i2c_prepare_for_io(kirkwood_i2c_msg);
-	kirkwood_i2c_doio(kirkwood_i2c_msg);
-	return drv_data->rc;
+	u8 dummy_byte;
+	int status;
+
+	/* begin i2c read */
+	status = i2c_begin(MVTWSI_STATUS_START, (chip << 1) | 1);
+	/* dummy read was accepted: receive byte but NAK it. */
+	if (status == 0)
+		status = twsi_recv(&dummy_byte);
+	/* Stop transaction */
+	twsi_stop(0);
+	/* return 0 or status of first failure */
+	return status;
 }
 
-int
-i2c_write(u8 dev, uint addr, int alen, u8 *data, int length)
+/*
+ * I2C read called by cmd_i2c when doing 'i2c read' and by cmd_eeprom.c
+ * Begin write, send address byte(s), begin read, receive data bytes, end.
+ *
+ * NOTE: some EEPROMS want a stop right before the second start, while
+ * some will choke if it is there. Deciding which we should do is eeprom
+ * stuff, not i2c, but at the moment the APIs won't let us put it in
+ * cmd_eeprom, so we have to choose here, and for the moment that'll be
+ * a repeated start without a preceding stop.
+ */
+int i2c_read(u8 dev, uint addr, int alen, u8 *data, int length)
 {
-	kirkwood_i2c_msg->buf = data;
-	kirkwood_i2c_msg->len = length;
-	kirkwood_i2c_msg->addr = dev;
-	kirkwood_i2c_msg->flags = 0;
-
-	kirkwood_i2c_prepare_for_io(kirkwood_i2c_msg);
-	kirkwood_i2c_doio(kirkwood_i2c_msg);
-	return drv_data->rc;
+	int status;
+
+	/* begin i2c write to send the address bytes */
+	status = i2c_begin(MVTWSI_STATUS_START, (dev << 1));
+	/* send addr bytes */
+	while ((status == 0) && alen--)
+		status = twsi_send(addr >> (8*alen),
+			MVTWSI_STATUS_DATA_W_ACK);
+	/* begin i2c read to receive eeprom data bytes */
+	if (status == 0)
+		status = i2c_begin(
+			MVTWSI_STATUS_REPEATED_START, (dev << 1) | 1);
+	/* prepare ACK if at least one byte must be received */
+	if (length > 0)
+		twsi_control_flags |= MVTWSI_CONTROL_ACK;
+	/* now receive actual bytes */
+	while ((status == 0) && length--) {
+		/* reset NAK if we if no more to read now */
+		if (length == 0)
+			twsi_control_flags &= ~MVTWSI_CONTROL_ACK;
+		/* read current byte */
+		status = twsi_recv(data++);
+	}
+	/* Stop transaction */
+	status = twsi_stop(status);
+	/* return 0 or status of first failure */
+	return status;
 }
 
-int
-i2c_probe(uchar chip)
+/*
+ * I2C write called by cmd_i2c when doing 'i2c write' and by cmd_eeprom.c
+ * Begin write, send address byte(s), send data bytes, end.
+ */
+int i2c_write(u8 dev, uint addr, int alen, u8 *data, int length)
 {
-	return i2c_read(chip, 0, 0, NULL, 0);
+	int status;
+
+	/* begin i2c write to send the eeprom adress bytes then data bytes */
+	status = i2c_begin(MVTWSI_STATUS_START, (dev << 1));
+	/* send addr bytes */
+	while ((status == 0) && alen--)
+		status = twsi_send(addr >> (8*alen),
+			MVTWSI_STATUS_DATA_W_ACK);
+	/* send data bytes */
+	while ((status == 0) && (length-- > 0))
+		status = twsi_send(*(data++), MVTWSI_STATUS_DATA_W_ACK);
+	/* Stop transaction */
+	status = twsi_stop(status);
+	/* return 0 or status of first failure */
+	return status;
 }
 
+/*
+ * Bus set routine: we only support bus 0.
+ */
 int i2c_set_bus_num(unsigned int bus)
 {
-#if defined(CONFIG_I2C_MUX)
-	if (bus < CONFIG_SYS_MAX_I2C_BUS) {
-		i2c_bus_num = bus;
-	} else {
-		int	ret;
-
-		ret = i2x_mux_select_mux(bus);
-		if (ret)
-			return ret;
-		i2c_bus_num = 0;
-	}
-	i2c_bus_num_mux = bus;
-#else
 	if (bus > 0) {
 		return -1;
 	}
-
-	i2c_bus_num = bus;
-#endif
 	return 0;
 }
 
+/*
+ * Bus get routine: hard-return bus 0.
+ */
 unsigned int i2c_get_bus_num(void)
 {
-#if defined(CONFIG_I2C_MUX)
-	return i2c_bus_num_mux;
-#else
-	return i2c_bus_num;
-#endif
+	return 0;
 }