i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver

Add Nuvoton NPCM BMC I2C controller driver.

Signed-off-by: Tali Perry <tali.perry1@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

3 files changed, 1746 insertions, 0 deletions

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 14e2e93a5698..735bf31a3fdf 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -794,6 +794,15 @@ config I2C_NOMADIK
 	  I2C interface from ST-Ericsson's Nomadik and Ux500 architectures,
 	  as well as the STA2X11 PCIe I/O HUB.
 
+config I2C_NPCM7XX
+	tristate "Nuvoton I2C Controller"
+	depends on ARCH_NPCM7XX || COMPILE_TEST
+	help
+	  If you say yes to this option, support will be included for the
+	  Nuvoton I2C controller, which is available on the NPCM7xx BMC
+	  controller.
+	  Driver can also support slave mode (select I2C_SLAVE).
+
 config I2C_OCORES
 	tristate "OpenCores I2C Controller"
 	help
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index e18497fb85c5..306d5dc3f417 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -80,6 +80,7 @@ obj-$(CONFIG_I2C_MT7621)	+= i2c-mt7621.o
 obj-$(CONFIG_I2C_MV64XXX)	+= i2c-mv64xxx.o
 obj-$(CONFIG_I2C_MXS)		+= i2c-mxs.o
 obj-$(CONFIG_I2C_NOMADIK)	+= i2c-nomadik.o
+obj-$(CONFIG_I2C_NPCM7XX)	+= i2c-npcm7xx.o
 obj-$(CONFIG_I2C_OCORES)	+= i2c-ocores.o
 obj-$(CONFIG_I2C_OMAP)		+= i2c-omap.o
 obj-$(CONFIG_I2C_OWL)		+= i2c-owl.o
diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
new file mode 100644
index 000000000000..018abf8dda7e
--- /dev/null
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -0,0 +1,1736 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NPCM7xx I2C Controller driver
+ *
+ * Copyright (C) 2020 Nuvoton Technologies tali.perry@nuvoton.com
+ */
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/debugfs.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/iopoll.h>
+#include <linux/irq.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+enum i2c_mode {
+	I2C_MASTER,
+	I2C_SLAVE,
+};
+
+/*
+ * External I2C Interface driver xfer indication values, which indicate status
+ * of the bus.
+ */
+enum i2c_state_ind {
+	I2C_NO_STATUS_IND = 0,
+	I2C_SLAVE_RCV_IND,
+	I2C_SLAVE_XMIT_IND,
+	I2C_SLAVE_XMIT_MISSING_DATA_IND,
+	I2C_SLAVE_RESTART_IND,
+	I2C_SLAVE_DONE_IND,
+	I2C_MASTER_DONE_IND,
+	I2C_NACK_IND,
+	I2C_BUS_ERR_IND,
+	I2C_WAKE_UP_IND,
+	I2C_BLOCK_BYTES_ERR_IND,
+	I2C_SLAVE_RCV_MISSING_DATA_IND,
+};
+
+/*
+ * Operation type values (used to define the operation currently running)
+ * module is interrupt driven, on each interrupt the current operation is
+ * checked to see if the module is currently reading or writing.
+ */
+enum i2c_oper {
+	I2C_NO_OPER = 0,
+	I2C_WRITE_OPER,
+	I2C_READ_OPER,
+};
+
+/* I2C Bank (module had 2 banks of registers) */
+enum i2c_bank {
+	I2C_BANK_0 = 0,
+	I2C_BANK_1,
+};
+
+/* Internal I2C states values (for the I2C module state machine). */
+enum i2c_state {
+	I2C_DISABLE = 0,
+	I2C_IDLE,
+	I2C_MASTER_START,
+	I2C_SLAVE_MATCH,
+	I2C_OPER_STARTED,
+	I2C_STOP_PENDING,
+};
+
+/* init register and default value required to enable module */
+#define NPCM_I2CSEGCTL			0xE4
+#define NPCM_I2CSEGCTL_INIT_VAL		0x0333F000
+
+/* Common regs */
+#define NPCM_I2CSDA			0x00
+#define NPCM_I2CST			0x02
+#define NPCM_I2CCST			0x04
+#define NPCM_I2CCTL1			0x06
+#define NPCM_I2CADDR1			0x08
+#define NPCM_I2CCTL2			0x0A
+#define NPCM_I2CADDR2			0x0C
+#define NPCM_I2CCTL3			0x0E
+#define NPCM_I2CCST2			0x18
+#define NPCM_I2CCST3			0x19
+#define I2C_VER				0x1F
+
+/*BANK0 regs*/
+#define NPCM_I2CADDR3			0x10
+#define NPCM_I2CADDR7			0x11
+#define NPCM_I2CADDR4			0x12
+#define NPCM_I2CADDR8			0x13
+#define NPCM_I2CADDR5			0x14
+#define NPCM_I2CADDR9			0x15
+#define NPCM_I2CADDR6			0x16
+#define NPCM_I2CADDR10			0x17
+
+#define NPCM_I2CCTL4			0x1A
+#define NPCM_I2CCTL5			0x1B
+#define NPCM_I2CSCLLT			0x1C /* SCL Low Time */
+#define NPCM_I2CFIF_CTL			0x1D /* FIFO Control */
+#define NPCM_I2CSCLHT			0x1E /* SCL High Time */
+
+/* BANK 1 regs */
+#define NPCM_I2CFIF_CTS			0x10 /* Both FIFOs Control and Status */
+#define NPCM_I2CTXF_CTL			0x12 /* Tx-FIFO Control */
+#define NPCM_I2CT_OUT			0x14 /* Bus T.O. */
+#define NPCM_I2CPEC			0x16 /* PEC Data */
+#define NPCM_I2CTXF_STS			0x1A /* Tx-FIFO Status */
+#define NPCM_I2CRXF_STS			0x1C /* Rx-FIFO Status */
+#define NPCM_I2CRXF_CTL			0x1E /* Rx-FIFO Control */
+
+/* NPCM_I2CST reg fields */
+#define NPCM_I2CST_XMIT			BIT(0)
+#define NPCM_I2CST_MASTER		BIT(1)
+#define NPCM_I2CST_NMATCH		BIT(2)
+#define NPCM_I2CST_STASTR		BIT(3)
+#define NPCM_I2CST_NEGACK		BIT(4)
+#define NPCM_I2CST_BER			BIT(5)
+#define NPCM_I2CST_SDAST		BIT(6)
+#define NPCM_I2CST_SLVSTP		BIT(7)
+
+/* NPCM_I2CCST reg fields */
+#define NPCM_I2CCST_BUSY		BIT(0)
+#define NPCM_I2CCST_BB			BIT(1)
+#define NPCM_I2CCST_MATCH		BIT(2)
+#define NPCM_I2CCST_GCMATCH		BIT(3)
+#define NPCM_I2CCST_TSDA		BIT(4)
+#define NPCM_I2CCST_TGSCL		BIT(5)
+#define NPCM_I2CCST_MATCHAF		BIT(6)
+#define NPCM_I2CCST_ARPMATCH		BIT(7)
+
+/* NPCM_I2CCTL1 reg fields */
+#define NPCM_I2CCTL1_START		BIT(0)
+#define NPCM_I2CCTL1_STOP		BIT(1)
+#define NPCM_I2CCTL1_INTEN		BIT(2)
+#define NPCM_I2CCTL1_EOBINTE		BIT(3)
+#define NPCM_I2CCTL1_ACK		BIT(4)
+#define NPCM_I2CCTL1_GCMEN		BIT(5)
+#define NPCM_I2CCTL1_NMINTE		BIT(6)
+#define NPCM_I2CCTL1_STASTRE		BIT(7)
+
+/* RW1S fields (inside a RW reg): */
+#define NPCM_I2CCTL1_RWS   \
+	(NPCM_I2CCTL1_START | NPCM_I2CCTL1_STOP | NPCM_I2CCTL1_ACK)
+
+/* npcm_i2caddr reg fields */
+#define NPCM_I2CADDR_A			GENMASK(6, 0)
+#define NPCM_I2CADDR_SAEN		BIT(7)
+
+/* NPCM_I2CCTL2 reg fields */
+#define I2CCTL2_ENABLE			BIT(0)
+#define I2CCTL2_SCLFRQ6_0		GENMASK(7, 1)
+
+/* NPCM_I2CCTL3 reg fields */
+#define I2CCTL3_SCLFRQ8_7		GENMASK(1, 0)
+#define I2CCTL3_ARPMEN			BIT(2)
+#define I2CCTL3_IDL_START		BIT(3)
+#define I2CCTL3_400K_MODE		BIT(4)
+#define I2CCTL3_BNK_SEL			BIT(5)
+#define I2CCTL3_SDA_LVL			BIT(6)
+#define I2CCTL3_SCL_LVL			BIT(7)
+
+/* NPCM_I2CCST2 reg fields */
+#define NPCM_I2CCST2_MATCHA1F		BIT(0)
+#define NPCM_I2CCST2_MATCHA2F		BIT(1)
+#define NPCM_I2CCST2_MATCHA3F		BIT(2)
+#define NPCM_I2CCST2_MATCHA4F		BIT(3)
+#define NPCM_I2CCST2_MATCHA5F		BIT(4)
+#define NPCM_I2CCST2_MATCHA6F		BIT(5)
+#define NPCM_I2CCST2_MATCHA7F		BIT(5)
+#define NPCM_I2CCST2_INTSTS		BIT(7)
+
+/* NPCM_I2CCST3 reg fields */
+#define NPCM_I2CCST3_MATCHA8F		BIT(0)
+#define NPCM_I2CCST3_MATCHA9F		BIT(1)
+#define NPCM_I2CCST3_MATCHA10F		BIT(2)
+#define NPCM_I2CCST3_EO_BUSY		BIT(7)
+
+/* NPCM_I2CCTL4 reg fields */
+#define I2CCTL4_HLDT			GENMASK(5, 0)
+#define I2CCTL4_LVL_WE			BIT(7)
+
+/* NPCM_I2CCTL5 reg fields */
+#define I2CCTL5_DBNCT			GENMASK(3, 0)
+
+/* NPCM_I2CFIF_CTS reg fields */
+#define NPCM_I2CFIF_CTS_RXF_TXE		BIT(1)
+#define NPCM_I2CFIF_CTS_RFTE_IE		BIT(3)
+#define NPCM_I2CFIF_CTS_CLR_FIFO	BIT(6)
+#define NPCM_I2CFIF_CTS_SLVRSTR		BIT(7)
+
+/* NPCM_I2CTXF_CTL reg fields */
+#define NPCM_I2CTXF_CTL_TX_THR		GENMASK(4, 0)
+#define NPCM_I2CTXF_CTL_THR_TXIE	BIT(6)
+
+/* NPCM_I2CT_OUT reg fields */
+#define NPCM_I2CT_OUT_TO_CKDIV		GENMASK(5, 0)
+#define NPCM_I2CT_OUT_T_OUTIE		BIT(6)
+#define NPCM_I2CT_OUT_T_OUTST		BIT(7)
+
+/* NPCM_I2CTXF_STS reg fields */
+#define NPCM_I2CTXF_STS_TX_BYTES	GENMASK(4, 0)
+#define NPCM_I2CTXF_STS_TX_THST		BIT(6)
+
+/* NPCM_I2CRXF_STS reg fields */
+#define NPCM_I2CRXF_STS_RX_BYTES	GENMASK(4, 0)
+#define NPCM_I2CRXF_STS_RX_THST		BIT(6)
+
+/* NPCM_I2CFIF_CTL reg fields */
+#define NPCM_I2CFIF_CTL_FIFO_EN		BIT(4)
+
+/* NPCM_I2CRXF_CTL reg fields */
+#define NPCM_I2CRXF_CTL_RX_THR		GENMASK(4, 0)
+#define NPCM_I2CRXF_CTL_LAST_PEC	BIT(5)
+#define NPCM_I2CRXF_CTL_THR_RXIE	BIT(6)
+
+#define I2C_HW_FIFO_SIZE		16
+
+/* I2C_VER reg fields */
+#define I2C_VER_VERSION			GENMASK(6, 0)
+#define I2C_VER_FIFO_EN			BIT(7)
+
+/* stall/stuck timeout in us */
+#define DEFAULT_STALL_COUNT		25
+
+/* SCLFRQ field position */
+#define SCLFRQ_0_TO_6			GENMASK(6, 0)
+#define SCLFRQ_7_TO_8			GENMASK(8, 7)
+
+/* supported clk settings. values in Hz. */
+#define I2C_FREQ_MIN_HZ			10000
+#define I2C_FREQ_MAX_HZ			I2C_MAX_FAST_MODE_PLUS_FREQ
+
+/* Status of one I2C module */
+struct npcm_i2c {
+	struct i2c_adapter adap;
+	struct device *dev;
+	unsigned char __iomem *reg;
+	spinlock_t lock;   /* IRQ synchronization */
+	struct completion cmd_complete;
+	int cmd_err;
+	struct i2c_msg *msgs;
+	int msgs_num;
+	int num;
+	u32 apb_clk;
+	struct i2c_bus_recovery_info rinfo;
+	enum i2c_state state;
+	enum i2c_oper operation;
+	enum i2c_mode master_or_slave;
+	enum i2c_state_ind stop_ind;
+	u8 dest_addr;
+	u8 *rd_buf;
+	u16 rd_size;
+	u16 rd_ind;
+	u8 *wr_buf;
+	u16 wr_size;
+	u16 wr_ind;
+	bool fifo_use;
+	u16 PEC_mask; /* PEC bit mask per slave address */
+	bool PEC_use;
+	bool read_block_use;
+	unsigned long int_time_stamp;
+	unsigned long bus_freq; /* in Hz */
+	struct dentry *debugfs; /* debugfs device directory */
+	u64 ber_cnt;
+	u64 rec_succ_cnt;
+	u64 rec_fail_cnt;
+	u64 nack_cnt;
+	u64 timeout_cnt;
+};
+
+static inline void npcm_i2c_select_bank(struct npcm_i2c *bus,
+					enum i2c_bank bank)
+{
+	u8 i2cctl3 = ioread8(bus->reg + NPCM_I2CCTL3);
+
+	if (bank == I2C_BANK_0)
+		i2cctl3 = i2cctl3 & ~I2CCTL3_BNK_SEL;
+	else
+		i2cctl3 = i2cctl3 | I2CCTL3_BNK_SEL;
+	iowrite8(i2cctl3, bus->reg + NPCM_I2CCTL3);
+}
+
+static void npcm_i2c_init_params(struct npcm_i2c *bus)
+{
+	bus->stop_ind = I2C_NO_STATUS_IND;
+	bus->rd_size = 0;
+	bus->wr_size = 0;
+	bus->rd_ind = 0;
+	bus->wr_ind = 0;
+	bus->read_block_use = false;
+	bus->int_time_stamp = 0;
+	bus->PEC_use = false;
+	bus->PEC_mask = 0;
+}
+
+static inline void npcm_i2c_wr_byte(struct npcm_i2c *bus, u8 data)
+{
+	iowrite8(data, bus->reg + NPCM_I2CSDA);
+}
+
+static inline u8 npcm_i2c_rd_byte(struct npcm_i2c *bus)
+{
+	return ioread8(bus->reg + NPCM_I2CSDA);
+}
+
+static int npcm_i2c_get_SCL(struct i2c_adapter *_adap)
+{
+	struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);
+
+	return !!(I2CCTL3_SCL_LVL & ioread32(bus->reg + NPCM_I2CCTL3));
+}
+
+static int npcm_i2c_get_SDA(struct i2c_adapter *_adap)
+{
+	struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);
+
+	return !!(I2CCTL3_SDA_LVL & ioread32(bus->reg + NPCM_I2CCTL3));
+}
+
+static inline u16 npcm_i2c_get_index(struct npcm_i2c *bus)
+{
+	if (bus->operation == I2C_READ_OPER)
+		return bus->rd_ind;
+	if (bus->operation == I2C_WRITE_OPER)
+		return bus->wr_ind;
+	return 0;
+}
+
+/* quick protocol (just address) */
+static inline bool npcm_i2c_is_quick(struct npcm_i2c *bus)
+{
+	return bus->wr_size == 0 && bus->rd_size == 0;
+}
+
+static void npcm_i2c_disable(struct npcm_i2c *bus)
+{
+	u8 i2cctl2;
+
+	/* Disable module */
+	i2cctl2 = ioread8(bus->reg + NPCM_I2CCTL2);
+	i2cctl2 = i2cctl2 & ~I2CCTL2_ENABLE;
+	iowrite8(i2cctl2, bus->reg + NPCM_I2CCTL2);
+
+	bus->state = I2C_DISABLE;
+}
+
+static void npcm_i2c_enable(struct npcm_i2c *bus)
+{
+	u8 i2cctl2 = ioread8(bus->reg + NPCM_I2CCTL2);
+
+	i2cctl2 = i2cctl2 | I2CCTL2_ENABLE;
+	iowrite8(i2cctl2, bus->reg + NPCM_I2CCTL2);
+	bus->state = I2C_IDLE;
+}
+
+/* enable\disable end of busy (EOB) interrupts */
+static inline void npcm_i2c_eob_int(struct npcm_i2c *bus, bool enable)
+{
+	u8 val;
+
+	/* Clear EO_BUSY pending bit: */
+	val = ioread8(bus->reg + NPCM_I2CCST3);
+	val = val | NPCM_I2CCST3_EO_BUSY;
+	iowrite8(val, bus->reg + NPCM_I2CCST3);
+
+	val = ioread8(bus->reg + NPCM_I2CCTL1);
+	val &= ~NPCM_I2CCTL1_RWS;
+	if (enable)
+		val |= NPCM_I2CCTL1_EOBINTE;
+	else
+		val &= ~NPCM_I2CCTL1_EOBINTE;
+	iowrite8(val, bus->reg + NPCM_I2CCTL1);
+}
+
+static inline bool npcm_i2c_tx_fifo_empty(struct npcm_i2c *bus)
+{
+	u8 tx_fifo_sts;
+
+	tx_fifo_sts = ioread8(bus->reg + NPCM_I2CTXF_STS);
+	/* check if TX FIFO is not empty */
+	if ((tx_fifo_sts & NPCM_I2CTXF_STS_TX_BYTES) == 0)
+		return false;
+
+	/* check if TX FIFO status bit is set: */
+	return !!FIELD_GET(NPCM_I2CTXF_STS_TX_THST, tx_fifo_sts);
+}
+
+static inline bool npcm_i2c_rx_fifo_full(struct npcm_i2c *bus)
+{
+	u8 rx_fifo_sts;
+
+	rx_fifo_sts = ioread8(bus->reg + NPCM_I2CRXF_STS);
+	/* check if RX FIFO is not empty: */
+	if ((rx_fifo_sts & NPCM_I2CRXF_STS_RX_BYTES) == 0)
+		return false;
+
+	/* check if rx fifo full status is set: */
+	return !!FIELD_GET(NPCM_I2CRXF_STS_RX_THST, rx_fifo_sts);
+}
+
+static inline void npcm_i2c_clear_fifo_int(struct npcm_i2c *bus)
+{
+	u8 val;
+
+	val = ioread8(bus->reg + NPCM_I2CFIF_CTS);
+	val = (val & NPCM_I2CFIF_CTS_SLVRSTR) | NPCM_I2CFIF_CTS_RXF_TXE;
+	iowrite8(val, bus->reg + NPCM_I2CFIF_CTS);
+}
+
+static inline void npcm_i2c_clear_tx_fifo(struct npcm_i2c *bus)
+{
+	u8 val;
+
+	val = ioread8(bus->reg + NPCM_I2CTXF_STS);
+	val = val | NPCM_I2CTXF_STS_TX_THST;
+	iowrite8(val, bus->reg + NPCM_I2CTXF_STS);
+}
+
+static inline void npcm_i2c_clear_rx_fifo(struct npcm_i2c *bus)
+{
+	u8 val;
+
+	val = ioread8(bus->reg + NPCM_I2CRXF_STS);
+	val = val | NPCM_I2CRXF_STS_RX_THST;
+	iowrite8(val, bus->reg + NPCM_I2CRXF_STS);
+}
+
+static void npcm_i2c_int_enable(struct npcm_i2c *bus, bool enable)
+{
+	u8 val;
+
+	val = ioread8(bus->reg + NPCM_I2CCTL1);
+	val &= ~NPCM_I2CCTL1_RWS;
+	if (enable)
+		val |= NPCM_I2CCTL1_INTEN;
+	else
+		val &= ~NPCM_I2CCTL1_INTEN;
+	iowrite8(val, bus->reg + NPCM_I2CCTL1);
+}
+
+static inline void npcm_i2c_master_start(struct npcm_i2c *bus)
+{
+	u8 val;
+
+	val = ioread8(bus->reg + NPCM_I2CCTL1);
+	val &= ~(NPCM_I2CCTL1_STOP | NPCM_I2CCTL1_ACK);
+	val |= NPCM_I2CCTL1_START;
+	iowrite8(val, bus->reg + NPCM_I2CCTL1);
+}
+
+static inline void npcm_i2c_master_stop(struct npcm_i2c *bus)
+{
+	u8 val;
+
+	/*
+	 * override HW issue: I2C may fail to supply stop condition in Master
+	 * Write operation.
+	 * Need to delay at least 5 us from the last int, before issueing a stop
+	 */
+	udelay(10); /* function called from interrupt, can't sleep */
+	val = ioread8(bus->reg + NPCM_I2CCTL1);
+	val &= ~(NPCM_I2CCTL1_START | NPCM_I2CCTL1_ACK);
+	val |= NPCM_I2CCTL1_STOP;
+	iowrite8(val, bus->reg + NPCM_I2CCTL1);
+
+	if (!bus->fifo_use)
+		return;
+
+	npcm_i2c_select_bank(bus, I2C_BANK_1);
+
+	if (bus->operation == I2C_READ_OPER)
+		npcm_i2c_clear_rx_fifo(bus);
+	else
+		npcm_i2c_clear_tx_fifo(bus);
+	npcm_i2c_clear_fifo_int(bus);
+	iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
+}
+
+static inline void npcm_i2c_stall_after_start(struct npcm_i2c *bus, bool stall)
+{
+	u8 val;
+
+	val = ioread8(bus->reg + NPCM_I2CCTL1);
+	val &= ~NPCM_I2CCTL1_RWS;
+	if (stall)
+		val |= NPCM_I2CCTL1_STASTRE;
+	else
+		val &= ~NPCM_I2CCTL1_STASTRE;
+	iowrite8(val, bus->reg + NPCM_I2CCTL1);
+}
+
+static inline void npcm_i2c_nack(struct npcm_i2c *bus)
+{
+	u8 val;
+
+	val = ioread8(bus->reg + NPCM_I2CCTL1);
+	val &= ~(NPCM_I2CCTL1_STOP | NPCM_I2CCTL1_START);
+	val |= NPCM_I2CCTL1_ACK;
+	iowrite8(val, bus->reg + NPCM_I2CCTL1);
+}
+
+static void npcm_i2c_reset(struct npcm_i2c *bus)
+{
+	/*
+	 * Save I2CCTL1 relevant bits. It is being cleared when the module
+	 *  is disabled.
+	 */
+	u8 i2cctl1;
+
+	i2cctl1 = ioread8(bus->reg + NPCM_I2CCTL1);
+
+	npcm_i2c_disable(bus);
+	npcm_i2c_enable(bus);
+
+	/* Restore NPCM_I2CCTL1 Status */
+	i2cctl1 &= ~NPCM_I2CCTL1_RWS;
+	iowrite8(i2cctl1, bus->reg + NPCM_I2CCTL1);
+
+	/* Clear BB (BUS BUSY) bit */
+	iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
+	iowrite8(0xFF, bus->reg + NPCM_I2CST);
+
+	/* Clear EOB bit */
+	iowrite8(NPCM_I2CCST3_EO_BUSY, bus->reg + NPCM_I2CCST3);
+
+	/* Clear all fifo bits: */
+	iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO, bus->reg + NPCM_I2CFIF_CTS);
+
+	bus->state = I2C_IDLE;
+}
+
+static inline bool npcm_i2c_is_master(struct npcm_i2c *bus)
+{
+	return !!FIELD_GET(NPCM_I2CST_MASTER, ioread8(bus->reg + NPCM_I2CST));
+}
+
+static void npcm_i2c_callback(struct npcm_i2c *bus,
+			      enum i2c_state_ind op_status, u16 info)
+{
+	struct i2c_msg *msgs;
+	int msgs_num;
+
+	msgs = bus->msgs;
+	msgs_num = bus->msgs_num;
+	/*
+	 * check that transaction was not timed-out, and msgs still
+	 * holds a valid value.
+	 */
+	if (!msgs)
+		return;
+
+	if (completion_done(&bus->cmd_complete))
+		return;
+
+	switch (op_status) {
+	case I2C_MASTER_DONE_IND:
+		bus->cmd_err = bus->msgs_num;
+		fallthrough;
+	case I2C_BLOCK_BYTES_ERR_IND:
+		/* Master tx finished and all transmit bytes were sent */
+		if (bus->msgs) {
+			if (msgs[0].flags & I2C_M_RD)
+				msgs[0].len = info;
+			else if (msgs_num == 2 &&
+				 msgs[1].flags & I2C_M_RD)
+				msgs[1].len = info;
+		}
+		if (completion_done(&bus->cmd_complete) == false)
+			complete(&bus->cmd_complete);
+	break;
+
+	case I2C_NACK_IND:
+		/* MASTER transmit got a NACK before tx all bytes */
+		bus->cmd_err = -ENXIO;
+		if (bus->master_or_slave == I2C_MASTER)
+			complete(&bus->cmd_complete);
+
+		break;
+	case I2C_BUS_ERR_IND:
+		/* Bus error */
+		bus->cmd_err = -EAGAIN;
+		if (bus->master_or_slave == I2C_MASTER)
+			complete(&bus->cmd_complete);
+
+		break;
+	case I2C_WAKE_UP_IND:
+		/* I2C wake up */
+		break;
+	default:
+		break;
+	}
+
+	bus->operation = I2C_NO_OPER;
+}
+
+static u8 npcm_i2c_fifo_usage(struct npcm_i2c *bus)
+{
+	if (bus->operation == I2C_WRITE_OPER)
+		return FIELD_GET(NPCM_I2CTXF_STS_TX_BYTES,
+				 ioread8(bus->reg + NPCM_I2CTXF_STS));
+	if (bus->operation == I2C_READ_OPER)
+		return FIELD_GET(NPCM_I2CRXF_STS_RX_BYTES,
+				 ioread8(bus->reg + NPCM_I2CRXF_STS));
+	return 0;
+}
+
+static void npcm_i2c_write_to_fifo_master(struct npcm_i2c *bus, u16 max_bytes)
+{
+	u8 size_free_fifo;
+
+	/*
+	 * Fill the FIFO, while the FIFO is not full and there are more bytes
+	 * to write
+	 */
+	size_free_fifo = I2C_HW_FIFO_SIZE - npcm_i2c_fifo_usage(bus);
+	while (max_bytes-- && size_free_fifo) {
+		if (bus->wr_ind < bus->wr_size)
+			npcm_i2c_wr_byte(bus, bus->wr_buf[bus->wr_ind++]);
+		else
+			npcm_i2c_wr_byte(bus, 0xFF);
+		size_free_fifo = I2C_HW_FIFO_SIZE - npcm_i2c_fifo_usage(bus);
+	}
+}
+
+/*
+ * npcm_i2c_set_fifo:
+ * configure the FIFO before using it. If nread is -1 RX FIFO will not be
+ * configured. same for nwrite
+ */
+static void npcm_i2c_set_fifo(struct npcm_i2c *bus, int nread, int nwrite)
+{
+	u8 rxf_ctl = 0;
+
+	if (!bus->fifo_use)
+		return;
+	npcm_i2c_select_bank(bus, I2C_BANK_1);
+	npcm_i2c_clear_tx_fifo(bus);
+	npcm_i2c_clear_rx_fifo(bus);
+
+	/* configure RX FIFO */
+	if (nread > 0) {
+		rxf_ctl = min_t(int, nread, I2C_HW_FIFO_SIZE);
+
+		/* set LAST bit. if LAST is set next FIFO packet is nacked */
+		if (nread <= I2C_HW_FIFO_SIZE)
+			rxf_ctl |= NPCM_I2CRXF_CTL_LAST_PEC;
+
+		/*
+		 * if we are about to read the first byte in blk rd mode,
+		 * don't NACK it. If slave returns zero size HW can't NACK
+		 * it immidiattly, it will read extra byte and then NACK.
+		 */
+		if (bus->rd_ind == 0 && bus->read_block_use) {
+			/* set fifo to read one byte, no last: */
+			rxf_ctl = 1;
+		}
+
+		/* set fifo size: */
+		iowrite8(rxf_ctl, bus->reg + NPCM_I2CRXF_CTL);
+	}
+
+	/* configure TX FIFO */
+	if (nwrite > 0) {
+		if (nwrite > I2C_HW_FIFO_SIZE)
+			/* data to send is more then FIFO size. */
+			iowrite8(I2C_HW_FIFO_SIZE, bus->reg + NPCM_I2CTXF_CTL);
+		else
+			iowrite8(nwrite, bus->reg + NPCM_I2CTXF_CTL);
+
+		npcm_i2c_clear_tx_fifo(bus);
+	}
+}
+
+static void npcm_i2c_read_fifo(struct npcm_i2c *bus, u8 bytes_in_fifo)
+{
+	u8 data;
+
+	while (bytes_in_fifo--) {
+		data = npcm_i2c_rd_byte(bus);
+		if (bus->rd_ind < bus->rd_size)
+			bus->rd_buf[bus->rd_ind++] = data;
+	}
+}
+
+static inline void npcm_i2c_clear_master_status(struct npcm_i2c *bus)
+{
+	u8 val;
+
+	/* Clear NEGACK, STASTR and BER bits */
+	val = NPCM_I2CST_BER | NPCM_I2CST_NEGACK | NPCM_I2CST_STASTR;
+	iowrite8(val, bus->reg + NPCM_I2CST);
+}
+
+static void npcm_i2c_master_abort(struct npcm_i2c *bus)
+{
+	/* Only current master is allowed to issue a stop condition */
+	if (!npcm_i2c_is_master(bus))
+		return;
+
+	npcm_i2c_eob_int(bus, true);
+	npcm_i2c_master_stop(bus);
+	npcm_i2c_clear_master_status(bus);
+}
+
+static void npcm_i2c_master_fifo_read(struct npcm_i2c *bus)
+{
+	int rcount;
+	int fifo_bytes;
+	enum i2c_state_ind ind = I2C_MASTER_DONE_IND;
+
+	fifo_bytes = npcm_i2c_fifo_usage(bus);
+	rcount = bus->rd_size - bus->rd_ind;
+
+	/*
+	 * In order not to change the RX_TRH during transaction (we found that
+	 * this might be problematic if it takes too much time to read the FIFO)
+	 * we read the data in the following way. If the number of bytes to
+	 * read == FIFO Size + C (where C < FIFO Size)then first read C bytes
+	 * and in the next int we read rest of the data.
+	 */
+	if (rcount < (2 * I2C_HW_FIFO_SIZE) && rcount > I2C_HW_FIFO_SIZE)
+		fifo_bytes = rcount - I2C_HW_FIFO_SIZE;
+
+	if (rcount <= fifo_bytes) {
+		/* last bytes are about to be read - end of tx */
+		bus->state = I2C_STOP_PENDING;
+		bus->stop_ind = ind;
+		npcm_i2c_eob_int(bus, true);
+		/* Stop should be set before reading last byte. */
+		npcm_i2c_master_stop(bus);
+		npcm_i2c_read_fifo(bus, fifo_bytes);
+	} else {
+		npcm_i2c_read_fifo(bus, fifo_bytes);
+		rcount = bus->rd_size - bus->rd_ind;
+		npcm_i2c_set_fifo(bus, rcount, -1);
+	}
+}
+
+static void npcm_i2c_irq_master_handler_write(struct npcm_i2c *bus)
+{
+	u16 wcount;
+
+	if (bus->fifo_use)
+		npcm_i2c_clear_tx_fifo(bus); /* clear the TX fifo status bit */
+
+	/* Master write operation - last byte handling */
+	if (bus->wr_ind == bus->wr_size) {
+		if (bus->fifo_use && npcm_i2c_fifo_usage(bus) > 0)
+			/*
+			 * No more bytes to send (to add to the FIFO),
+			 * however the FIFO is not empty yet. It is
+			 * still in the middle of tx. Currently there's nothing
+			 * to do except for waiting to the end of the tx
+			 * We will get an int when the FIFO will get empty.
+			 */
+			return;
+
+		if (bus->rd_size == 0) {
+			/* all bytes have been written, in wr only operation */
+			npcm_i2c_eob_int(bus, true);
+			bus->state = I2C_STOP_PENDING;
+			bus->stop_ind = I2C_MASTER_DONE_IND;
+			npcm_i2c_master_stop(bus);
+			/* Clear SDA Status bit (by writing dummy byte) */
+			npcm_i2c_wr_byte(bus, 0xFF);
+
+		} else {
+			/* last write-byte written on previous int - restart */
+			npcm_i2c_set_fifo(bus, bus->rd_size, -1);
+			/* Generate repeated start upon next write to SDA */
+			npcm_i2c_master_start(bus);
+
+			/*
+			 * Receiving one byte only - stall after successful
+			 * completion of send address byte. If we NACK here, and
+			 * slave doesn't ACK the address, we might
+			 * unintentionally NACK the next multi-byte read.
+			 */
+			if (bus->rd_size == 1)
+				npcm_i2c_stall_after_start(bus, true);
+
+			/* Next int will occur on read */
+			bus->operation = I2C_READ_OPER;
+			/* send the slave address in read direction */
+			npcm_i2c_wr_byte(bus, bus->dest_addr | 0x1);
+		}
+	} else {
+		/* write next byte not last byte and not slave address */
+		if (!bus->fifo_use || bus->wr_size == 1) {
+			npcm_i2c_wr_byte(bus, bus->wr_buf[bus->wr_ind++]);
+		} else {
+			wcount = bus->wr_size - bus->wr_ind;
+			npcm_i2c_set_fifo(bus, -1, wcount);
+			if (wcount)
+				npcm_i2c_write_to_fifo_master(bus, wcount);
+		}
+	}
+}
+
+static void npcm_i2c_irq_master_handler_read(struct npcm_i2c *bus)
+{
+	u16 block_extra_bytes_size;
+	u8 data;
+
+	/* added bytes to the packet: */
+	block_extra_bytes_size = bus->read_block_use + bus->PEC_use;
+
+	/*
+	 * Perform master read, distinguishing between last byte and the rest of
+	 * the bytes. The last byte should be read when the clock is stopped
+	 */
+	if (bus->rd_ind == 0) { /* first byte handling: */
+		if (bus->read_block_use) {
+			/* first byte in block protocol is the size: */
+			data = npcm_i2c_rd_byte(bus);
+			data = clamp_val(data, 1, I2C_SMBUS_BLOCK_MAX);
+			bus->rd_size = data + block_extra_bytes_size;
+			bus->rd_buf[bus->rd_ind++] = data;
+
+			/* clear RX FIFO interrupt status: */
+			if (bus->fifo_use) {
+				data = ioread8(bus->reg + NPCM_I2CFIF_CTS);
+				data = data | NPCM_I2CFIF_CTS_RXF_TXE;
+				iowrite8(data, bus->reg + NPCM_I2CFIF_CTS);
+			}
+
+			npcm_i2c_set_fifo(bus, bus->rd_size - 1, -1);
+			npcm_i2c_stall_after_start(bus, false);
+		} else {
+			npcm_i2c_clear_tx_fifo(bus);
+			npcm_i2c_master_fifo_read(bus);
+		}
+	} else {
+		if (bus->rd_size == block_extra_bytes_size &&
+		    bus->read_block_use) {
+			bus->state = I2C_STOP_PENDING;
+			bus->stop_ind = I2C_BLOCK_BYTES_ERR_IND;
+			bus->cmd_err = -EIO;
+			npcm_i2c_eob_int(bus, true);
+			npcm_i2c_master_stop(bus);
+			npcm_i2c_read_fifo(bus, npcm_i2c_fifo_usage(bus));
+		} else {
+			npcm_i2c_master_fifo_read(bus);
+		}
+	}
+}
+
+static void npcm_i2c_irq_handle_nmatch(struct npcm_i2c *bus)
+{
+	iowrite8(NPCM_I2CST_NMATCH, bus->reg + NPCM_I2CST);
+	npcm_i2c_nack(bus);
+	bus->stop_ind = I2C_BUS_ERR_IND;
+	npcm_i2c_callback(bus, bus->stop_ind, npcm_i2c_get_index(bus));
+}
+
+/* A NACK has occurred */
+static void npcm_i2c_irq_handle_nack(struct npcm_i2c *bus)
+{
+	u8 val;
+
+	if (bus->nack_cnt < ULLONG_MAX)
+		bus->nack_cnt++;
+
+	if (bus->fifo_use) {
+		/*
+		 * if there are still untransmitted bytes in TX FIFO
+		 * reduce them from wr_ind
+		 */
+		if (bus->operation == I2C_WRITE_OPER)
+			bus->wr_ind -= npcm_i2c_fifo_usage(bus);
+
+		/* clear the FIFO */
+		iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO, bus->reg + NPCM_I2CFIF_CTS);
+	}
+
+	/* In master write operation, got unexpected NACK */
+	bus->stop_ind = I2C_NACK_IND;
+	/* Only current master is allowed to issue Stop Condition */
+	if (npcm_i2c_is_master(bus)) {
+		/* stopping in the middle */
+		npcm_i2c_eob_int(bus, false);
+		npcm_i2c_master_stop(bus);
+
+		/*
+		 * The bus is released from stall only after the SW clears
+		 * NEGACK bit. Then a Stop condition is sent.
+		 */
+		npcm_i2c_clear_master_status(bus);
+		readx_poll_timeout_atomic(ioread8, bus->reg + NPCM_I2CCST, val,
+					  !(val & NPCM_I2CCST_BUSY), 10, 200);
+	}
+	bus->state = I2C_IDLE;
+
+	/*
+	 * In Master mode, NACK should be cleared only after STOP.
+	 * In such case, the bus is released from stall only after the
+	 * software clears NACK bit. Then a Stop condition is sent.
+	 */
+	npcm_i2c_callback(bus, bus->stop_ind, bus->wr_ind);
+}
+
+	/* Master mode: a Bus Error has been identified */
+static void npcm_i2c_irq_handle_ber(struct npcm_i2c *bus)
+{
+	if (bus->ber_cnt < ULLONG_MAX)
+		bus->ber_cnt++;
+	bus->stop_ind = I2C_BUS_ERR_IND;
+	if (npcm_i2c_is_master(bus)) {
+		npcm_i2c_master_abort(bus);
+	} else {
+		npcm_i2c_clear_master_status(bus);
+
+		/* Clear BB (BUS BUSY) bit */
+		iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
+
+		bus->cmd_err = -EAGAIN;
+		npcm_i2c_callback(bus, bus->stop_ind, npcm_i2c_get_index(bus));
+	}
+	bus->state = I2C_IDLE;
+}
+
+	/* EOB: a master End Of Busy (meaning STOP completed) */
+static void npcm_i2c_irq_handle_eob(struct npcm_i2c *bus)
+{
+	npcm_i2c_eob_int(bus, false);
+	bus->state = I2C_IDLE;
+	npcm_i2c_callback(bus, bus->stop_ind, bus->rd_ind);
+}
+
+/* Address sent and requested stall occurred (Master mode) */
+static void npcm_i2c_irq_handle_stall_after_start(struct npcm_i2c *bus)
+{
+	if (npcm_i2c_is_quick(bus)) {
+		bus->state = I2C_STOP_PENDING;
+		bus->stop_ind = I2C_MASTER_DONE_IND;
+		npcm_i2c_eob_int(bus, true);
+		npcm_i2c_master_stop(bus);
+	} else if ((bus->rd_size == 1) && !bus->read_block_use) {
+		/*
+		 * Receiving one byte only - set NACK after ensuring
+		 * slave ACKed the address byte.
+		 */
+		npcm_i2c_nack(bus);
+	}
+
+	/* Reset stall-after-address-byte */
+	npcm_i2c_stall_after_start(bus, false);
+
+	/* Clear stall only after setting STOP */
+	iowrite8(NPCM_I2CST_STASTR, bus->reg + NPCM_I2CST);
+}
+
+/* SDA status is set - TX or RX, master */
+static void npcm_i2c_irq_handle_sda(struct npcm_i2c *bus, u8 i2cst)
+{
+	u8 fif_cts;
+
+	if (!npcm_i2c_is_master(bus))
+		return;
+
+	if (bus->state == I2C_IDLE) {
+		bus->stop_ind = I2C_WAKE_UP_IND;
+
+		if (npcm_i2c_is_quick(bus) || bus->read_block_use)
+			/*
+			 * Need to stall after successful
+			 * completion of sending address byte
+			 */
+			npcm_i2c_stall_after_start(bus, true);
+		else
+			npcm_i2c_stall_after_start(bus, false);
+
+		/*
+		 * Receiving one byte only - stall after successful completion
+		 * of sending address byte If we NACK here, and slave doesn't
+		 * ACK the address, we might unintentionally NACK the next
+		 * multi-byte read
+		 */
+		if (bus->wr_size == 0 && bus->rd_size == 1)
+			npcm_i2c_stall_after_start(bus, true);
+
+		/* Initiate I2C master tx */
+
+		/* select bank 1 for FIFO regs */
+		npcm_i2c_select_bank(bus, I2C_BANK_1);
+
+		fif_cts = ioread8(bus->reg + NPCM_I2CFIF_CTS);
+		fif_cts = fif_cts & ~NPCM_I2CFIF_CTS_SLVRSTR;
+
+		/* clear FIFO and relevant status bits. */
+		fif_cts = fif_cts | NPCM_I2CFIF_CTS_CLR_FIFO;
+		iowrite8(fif_cts, bus->reg + NPCM_I2CFIF_CTS);
+
+		/* re-enable */
+		fif_cts = fif_cts | NPCM_I2CFIF_CTS_RXF_TXE;
+		iowrite8(fif_cts, bus->reg + NPCM_I2CFIF_CTS);
+
+		/*
+		 * Configure the FIFO threshold:
+		 * according to the needed # of bytes to read.
+		 * Note: due to HW limitation can't config the rx fifo before it
+		 * got and ACK on the restart. LAST bit will not be reset unless
+		 * RX completed. It will stay set on the next tx.
+		 */
+		if (bus->wr_size)
+			npcm_i2c_set_fifo(bus, -1, bus->wr_size);
+		else
+			npcm_i2c_set_fifo(bus, bus->rd_size, -1);
+
+		bus->state = I2C_OPER_STARTED;
+
+		if (npcm_i2c_is_quick(bus) || bus->wr_size)
+			npcm_i2c_wr_byte(bus, bus->dest_addr);
+		else
+			npcm_i2c_wr_byte(bus, bus->dest_addr | BIT(0));
+	/* SDA interrupt, after start\restart */
+	} else {
+		if (NPCM_I2CST_XMIT & i2cst) {
+			bus->operation = I2C_WRITE_OPER;
+			npcm_i2c_irq_master_handler_write(bus);
+		} else {
+			bus->operation = I2C_READ_OPER;
+			npcm_i2c_irq_master_handler_read(bus);
+		}
+	}
+}
+
+static int npcm_i2c_int_master_handler(struct npcm_i2c *bus)
+{
+	u8 i2cst;
+	int ret = -EIO;
+
+	i2cst = ioread8(bus->reg + NPCM_I2CST);
+
+	if (FIELD_GET(NPCM_I2CST_NMATCH, i2cst)) {
+		npcm_i2c_irq_handle_nmatch(bus);
+		return 0;
+	}
+	/* A NACK has occurred */
+	if (FIELD_GET(NPCM_I2CST_NEGACK, i2cst)) {
+		npcm_i2c_irq_handle_nack(bus);
+		return 0;
+	}
+
+	/* Master mode: a Bus Error has been identified */
+	if (FIELD_GET(NPCM_I2CST_BER, i2cst)) {
+		npcm_i2c_irq_handle_ber(bus);
+		return 0;
+	}
+
+	/* EOB: a master End Of Busy (meaning STOP completed) */
+	if ((FIELD_GET(NPCM_I2CCTL1_EOBINTE,
+		       ioread8(bus->reg + NPCM_I2CCTL1)) == 1) &&
+	    (FIELD_GET(NPCM_I2CCST3_EO_BUSY,
+		       ioread8(bus->reg + NPCM_I2CCST3)))) {
+		npcm_i2c_irq_handle_eob(bus);
+		return 0;
+	}
+
+	/* Address sent and requested stall occurred (Master mode) */
+	if (FIELD_GET(NPCM_I2CST_STASTR, i2cst)) {
+		npcm_i2c_irq_handle_stall_after_start(bus);
+		ret = 0;
+	}
+
+	/* SDA status is set - TX or RX, master */
+	if (FIELD_GET(NPCM_I2CST_SDAST, i2cst) ||
+	    (bus->fifo_use &&
+	    (npcm_i2c_tx_fifo_empty(bus) || npcm_i2c_rx_fifo_full(bus)))) {
+		npcm_i2c_irq_handle_sda(bus, i2cst);
+		ret = 0;
+	}
+
+	return ret;
+}
+
+/* recovery using TGCLK functionality of the module */
+static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
+{
+	u8               val;
+	u8               fif_cts;
+	bool             done = false;
+	int              status = -ENOTRECOVERABLE;
+	struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);
+	/* Allow 3 bytes (27 toggles) to be read from the slave: */
+	int              iter = 27;
+
+	if ((npcm_i2c_get_SDA(_adap) == 1) && (npcm_i2c_get_SCL(_adap) == 1)) {
+		dev_dbg(bus->dev, "bus%d recovery skipped, bus not stuck",
+			bus->num);
+		npcm_i2c_reset(bus);
+		return status;
+	}
+
+	npcm_i2c_int_enable(bus, false);
+	npcm_i2c_disable(bus);
+	npcm_i2c_enable(bus);
+	iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
+	npcm_i2c_clear_tx_fifo(bus);
+	npcm_i2c_clear_rx_fifo(bus);
+	iowrite8(0, bus->reg + NPCM_I2CRXF_CTL);
+	iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
+	npcm_i2c_stall_after_start(bus, false);
+
+	/* select bank 1 for FIFO regs */
+	npcm_i2c_select_bank(bus, I2C_BANK_1);
+
+	/* clear FIFO and relevant status bits. */
+	fif_cts = ioread8(bus->reg + NPCM_I2CFIF_CTS);
+	fif_cts &= ~NPCM_I2CFIF_CTS_SLVRSTR;
+	fif_cts |= NPCM_I2CFIF_CTS_CLR_FIFO;
+	iowrite8(fif_cts, bus->reg + NPCM_I2CFIF_CTS);
+	npcm_i2c_set_fifo(bus, -1, 0);
+
+	/* Repeat the following sequence until SDA is released */
+	do {
+		/* Issue a single SCL toggle */
+		iowrite8(NPCM_I2CCST_TGSCL, bus->reg + NPCM_I2CCST);
+		usleep_range(20, 30);
+		/* If SDA line is inactive (high), stop */
+		if (npcm_i2c_get_SDA(_adap)) {
+			done = true;
+			status = 0;
+		}
+	} while (!done && iter--);
+
+	/* If SDA line is released: send start-addr-stop, to re-sync. */
+	if (npcm_i2c_get_SDA(_adap)) {
+		/* Send an address byte in write direction: */
+		npcm_i2c_wr_byte(bus, bus->dest_addr);
+		npcm_i2c_master_start(bus);
+		/* Wait until START condition is sent */
+		status = readx_poll_timeout(npcm_i2c_get_SCL, _adap, val, !val,
+					    20, 200);
+		/* If START condition was sent */
+		if (npcm_i2c_is_master(bus) > 0) {
+			usleep_range(20, 30);
+			npcm_i2c_master_stop(bus);
+			usleep_range(200, 500);
+		}
+	}
+	npcm_i2c_reset(bus);
+	npcm_i2c_int_enable(bus, true);
+
+	if ((npcm_i2c_get_SDA(_adap) == 1) && (npcm_i2c_get_SCL(_adap) == 1))
+		status = 0;
+	else
+		status = -ENOTRECOVERABLE;
+	if (status) {
+		if (bus->rec_fail_cnt < ULLONG_MAX)
+			bus->rec_fail_cnt++;
+	} else {
+		if (bus->rec_succ_cnt < ULLONG_MAX)
+			bus->rec_succ_cnt++;
+	}
+	return status;
+}
+
+/* recovery using bit banging functionality of the module */
+static void npcm_i2c_recovery_init(struct i2c_adapter *_adap)
+{
+	struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);
+	struct i2c_bus_recovery_info *rinfo = &bus->rinfo;
+
+	rinfo->recover_bus = npcm_i2c_recovery_tgclk;
+
+	/*
+	 * npcm i2c HW allows direct reading of SCL and SDA.
+	 * However, it does not support setting SCL and SDA directly.
+	 * The recovery function can togle SCL when SDA is low (but not set)
+	 * Getter functions used internally, and can be used externaly.
+	 */
+	rinfo->get_scl = npcm_i2c_get_SCL;
+	rinfo->get_sda = npcm_i2c_get_SDA;
+	_adap->bus_recovery_info = rinfo;
+}
+
+/* SCLFRQ min/max field values */
+#define SCLFRQ_MIN  10
+#define SCLFRQ_MAX  511
+#define clk_coef(freq, mul)	DIV_ROUND_UP((freq) * (mul), 1000000)
+
+/*
+ * npcm_i2c_init_clk: init HW timing parameters.
+ * NPCM7XX i2c module timing parameters are depenent on module core clk (APB)
+ * and bus frequency.
+ * 100kHz bus requires tSCL = 4 * SCLFRQ * tCLK. LT and HT are simetric.
+ * 400kHz bus requires assymetric HT and LT. A different equation is recomended
+ * by the HW designer, given core clock range (equations in comments below).
+ *
+ */
+static int npcm_i2c_init_clk(struct npcm_i2c *bus, u32 bus_freq_hz)
+{
+	u32  k1 = 0;
+	u32  k2 = 0;
+	u8   dbnct = 0;
+	u32  sclfrq = 0;
+	u8   hldt = 7;
+	u8   fast_mode = 0;
+	u32  src_clk_khz;
+	u32  bus_freq_khz;
+
+	src_clk_khz = bus->apb_clk / 1000;
+	bus_freq_khz = bus_freq_hz / 1000;
+	bus->bus_freq = bus_freq_hz;
+
+	/* 100KHz and below: */
+	if (bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ) {
+		sclfrq = src_clk_khz / (bus_freq_khz * 4);
+
+		if (sclfrq < SCLFRQ_MIN || sclfrq > SCLFRQ_MAX)
+			return -EDOM;
+
+		if (src_clk_khz >= 40000)
+			hldt = 17;
+		else if (src_clk_khz >= 12500)
+			hldt = 15;
+		else
+			hldt = 7;
+	}
+
+	/* 400KHz: */
+	else if (bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ) {
+		sclfrq = 0;
+		fast_mode = I2CCTL3_400K_MODE;
+
+		if (src_clk_khz < 7500)
+			/* 400KHZ cannot be supported for core clock < 7.5MHz */
+			return -EDOM;
+
+		else if (src_clk_khz >= 50000) {
+			k1 = 80;
+			k2 = 48;
+			hldt = 12;
+			dbnct = 7;
+		}
+
+		/* Master or Slave with frequency > 25MHz */
+		else if (src_clk_khz > 25000) {
+			hldt = clk_coef(src_clk_khz, 300) + 7;
+			k1 = clk_coef(src_clk_khz, 1600);
+			k2 = clk_coef(src_clk_khz, 900);
+		}
+	}
+
+	/* 1MHz: */
+	else if (bus_freq_hz <= I2C_MAX_FAST_MODE_PLUS_FREQ) {
+		sclfrq = 0;
+		fast_mode = I2CCTL3_400K_MODE;
+
+		/* 1MHZ cannot be supported for core clock < 24 MHz */
+		if (src_clk_khz < 24000)
+			return -EDOM;
+
+		k1 = clk_coef(src_clk_khz, 620);
+		k2 = clk_coef(src_clk_khz, 380);
+
+		/* Core clk > 40 MHz */
+		if (src_clk_khz > 40000) {
+			/*
+			 * Set HLDT:
+			 * SDA hold time:  (HLDT-7) * T(CLK) >= 120
+			 * HLDT = 120/T(CLK) + 7 = 120 * FREQ(CLK) + 7
+			 */
+			hldt = clk_coef(src_clk_khz, 120) + 7;
+		} else {
+			hldt = 7;
+			dbnct = 2;
+		}
+	}
+
+	/* Frequency larger than 1 MHz is not supported */
+	else
+		return -EINVAL;
+
+	if (bus_freq_hz >= I2C_MAX_FAST_MODE_FREQ) {
+		k1 = round_up(k1, 2);
+		k2 = round_up(k2 + 1, 2);
+		if (k1 < SCLFRQ_MIN || k1 > SCLFRQ_MAX ||
+		    k2 < SCLFRQ_MIN || k2 > SCLFRQ_MAX)
+			return -EDOM;
+	}
+
+	/* write sclfrq value. bits [6:0] are in I2CCTL2 reg */
+	iowrite8(FIELD_PREP(I2CCTL2_SCLFRQ6_0, sclfrq & 0x7F),
+		 bus->reg + NPCM_I2CCTL2);
+
+	/* bits [8:7] are in I2CCTL3 reg */
+	iowrite8(fast_mode | FIELD_PREP(I2CCTL3_SCLFRQ8_7, (sclfrq >> 7) & 0x3),
+		 bus->reg + NPCM_I2CCTL3);
+
+	/* Select Bank 0 to access NPCM_I2CCTL4/NPCM_I2CCTL5 */
+	npcm_i2c_select_bank(bus, I2C_BANK_0);
+
+	if (bus_freq_hz >= I2C_MAX_FAST_MODE_FREQ) {
+		/*
+		 * Set SCL Low/High Time:
+		 * k1 = 2 * SCLLT7-0 -> Low Time  = k1 / 2
+		 * k2 = 2 * SCLLT7-0 -> High Time = k2 / 2
+		 */
+		iowrite8(k1 / 2, bus->reg + NPCM_I2CSCLLT);
+		iowrite8(k2 / 2, bus->reg + NPCM_I2CSCLHT);
+
+		iowrite8(dbnct, bus->reg + NPCM_I2CCTL5);
+	}
+
+	iowrite8(hldt, bus->reg + NPCM_I2CCTL4);
+
+	/* Return to Bank 1, and stay there by default: */
+	npcm_i2c_select_bank(bus, I2C_BANK_1);
+
+	return 0;
+}
+
+static int npcm_i2c_init_module(struct npcm_i2c *bus, enum i2c_mode mode,
+				u32 bus_freq_hz)
+{
+	u8 val;
+	int ret;
+
+	/* Check whether module already enabled or frequency is out of bounds */
+	if ((bus->state != I2C_DISABLE && bus->state != I2C_IDLE) ||
+	    bus_freq_hz < I2C_FREQ_MIN_HZ || bus_freq_hz > I2C_FREQ_MAX_HZ)
+		return -EINVAL;
+
+	npcm_i2c_disable(bus);
+
+	/* Configure FIFO mode : */
+	if (FIELD_GET(I2C_VER_FIFO_EN, ioread8(bus->reg + I2C_VER))) {
+		bus->fifo_use = true;
+		npcm_i2c_select_bank(bus, I2C_BANK_0);
+		val = ioread8(bus->reg + NPCM_I2CFIF_CTL);
+		val |= NPCM_I2CFIF_CTL_FIFO_EN;
+		iowrite8(val, bus->reg + NPCM_I2CFIF_CTL);
+		npcm_i2c_select_bank(bus, I2C_BANK_1);
+	} else {
+		bus->fifo_use = false;
+	}
+
+	/* Configure I2C module clock frequency */
+	ret = npcm_i2c_init_clk(bus, bus_freq_hz);
+	if (ret) {
+		dev_err(bus->dev, "npcm_i2c_init_clk failed\n");
+		return ret;
+	}
+
+	/* Enable module (before configuring CTL1) */
+	npcm_i2c_enable(bus);
+	bus->state = I2C_IDLE;
+	val = ioread8(bus->reg + NPCM_I2CCTL1);
+	val = (val | NPCM_I2CCTL1_NMINTE) & ~NPCM_I2CCTL1_RWS;
+	iowrite8(val, bus->reg + NPCM_I2CCTL1);
+
+	npcm_i2c_int_enable(bus, true);
+
+	npcm_i2c_reset(bus);
+
+	return 0;
+}
+
+static int __npcm_i2c_init(struct npcm_i2c *bus, struct platform_device *pdev)
+{
+	u32 clk_freq_hz;
+	int ret;
+
+	/* Initialize the internal data structures */
+	bus->state = I2C_DISABLE;
+	bus->master_or_slave = I2C_SLAVE;
+	bus->int_time_stamp = 0;
+
+	ret = device_property_read_u32(&pdev->dev, "clock-frequency",
+				       &clk_freq_hz);
+	if (ret) {
+		dev_info(&pdev->dev, "Could not read clock-frequency property");
+		clk_freq_hz = I2C_MAX_STANDARD_MODE_FREQ;
+	}
+
+	ret = npcm_i2c_init_module(bus, I2C_MASTER, clk_freq_hz);
+	if (ret) {
+		dev_err(&pdev->dev, "npcm_i2c_init_module failed\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static irqreturn_t npcm_i2c_bus_irq(int irq, void *dev_id)
+{
+	struct npcm_i2c *bus = dev_id;
+
+	if (npcm_i2c_is_master(bus))
+		bus->master_or_slave = I2C_MASTER;
+
+	if (bus->master_or_slave == I2C_MASTER) {
+		bus->int_time_stamp = jiffies;
+		if (!npcm_i2c_int_master_handler(bus))
+			return IRQ_HANDLED;
+	}
+	return IRQ_NONE;
+}
+
+static bool npcm_i2c_master_start_xmit(struct npcm_i2c *bus,
+				       u8 slave_addr, u16 nwrite, u16 nread,
+				       u8 *write_data, u8 *read_data,
+				       bool use_PEC, bool use_read_block)
+{
+	if (bus->state != I2C_IDLE) {
+		bus->cmd_err = -EBUSY;
+		return false;
+	}
+	bus->dest_addr = slave_addr << 1;
+	bus->wr_buf = write_data;
+	bus->wr_size = nwrite;
+	bus->wr_ind = 0;
+	bus->rd_buf = read_data;
+	bus->rd_size = nread;
+	bus->rd_ind = 0;
+	bus->PEC_use = 0;
+
+	/* for tx PEC is appended to buffer from i2c IF. PEC flag is ignored */
+	if (nread)
+		bus->PEC_use = use_PEC;
+
+	bus->read_block_use = use_read_block;
+	if (nread && !nwrite)
+		bus->operation = I2C_READ_OPER;
+	else
+		bus->operation = I2C_WRITE_OPER;
+	if (bus->fifo_use) {
+		u8 i2cfif_cts;
+
+		npcm_i2c_select_bank(bus, I2C_BANK_1);
+		/* clear FIFO and relevant status bits. */
+		i2cfif_cts = ioread8(bus->reg + NPCM_I2CFIF_CTS);
+		i2cfif_cts &= ~NPCM_I2CFIF_CTS_SLVRSTR;
+		i2cfif_cts |= NPCM_I2CFIF_CTS_CLR_FIFO;
+		iowrite8(i2cfif_cts, bus->reg + NPCM_I2CFIF_CTS);
+	}
+
+	bus->state = I2C_IDLE;
+	npcm_i2c_stall_after_start(bus, true);
+	npcm_i2c_master_start(bus);
+	return true;
+}
+
+static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+				int num)
+{
+	struct npcm_i2c *bus = container_of(adap, struct npcm_i2c, adap);
+	struct i2c_msg *msg0, *msg1;
+	unsigned long time_left, flags;
+	u16 nwrite, nread;
+	u8 *write_data, *read_data;
+	u8 slave_addr;
+	int timeout;
+	int ret = 0;
+	bool read_block = false;
+	bool read_PEC = false;
+	u8 bus_busy;
+	unsigned long timeout_usec;
+
+	if (bus->state == I2C_DISABLE) {
+		dev_err(bus->dev, "I2C%d module is disabled", bus->num);
+		return -EINVAL;
+	}
+
+	msg0 = &msgs[0];
+	slave_addr = msg0->addr;
+	if (msg0->flags & I2C_M_RD) { /* read */
+		nwrite = 0;
+		write_data = NULL;
+		read_data = msg0->buf;
+		if (msg0->flags & I2C_M_RECV_LEN) {
+			nread = 1;
+			read_block = true;
+			if (msg0->flags & I2C_CLIENT_PEC)
+				read_PEC = true;
+		} else {
+			nread = msg0->len;
+		}
+	} else { /* write */
+		nwrite = msg0->len;
+		write_data = msg0->buf;
+		nread = 0;
+		read_data = NULL;
+		if (num == 2) {
+			msg1 = &msgs[1];
+			read_data = msg1->buf;
+			if (msg1->flags & I2C_M_RECV_LEN) {
+				nread = 1;
+				read_block = true;
+				if (msg1->flags & I2C_CLIENT_PEC)
+					read_PEC = true;
+			} else {
+				nread = msg1->len;
+				read_block = false;
+			}
+		}
+	}
+
+	/* Adaptive TimeOut: astimated time in usec + 100% margin */
+	timeout_usec = (2 * 10000 / bus->bus_freq) * (2 + nread + nwrite);
+	timeout = max(msecs_to_jiffies(35), usecs_to_jiffies(timeout_usec));
+	if (nwrite >= 32 * 1024 || nread >= 32 * 1024) {
+		dev_err(bus->dev, "i2c%d buffer too big\n", bus->num);
+		return -EINVAL;
+	}
+
+	time_left = jiffies + msecs_to_jiffies(DEFAULT_STALL_COUNT) + 1;
+	do {
+		/*
+		 * we must clear slave address immediately when the bus is not
+		 * busy, so we spinlock it, but we don't keep the lock for the
+		 * entire while since it is too long.
+		 */
+		spin_lock_irqsave(&bus->lock, flags);
+		bus_busy = ioread8(bus->reg + NPCM_I2CCST) & NPCM_I2CCST_BB;
+		spin_unlock_irqrestore(&bus->lock, flags);
+
+	} while (time_is_after_jiffies(time_left) && bus_busy);
+
+	if (bus_busy) {
+		iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
+		npcm_i2c_reset(bus);
+		i2c_recover_bus(adap);
+		return -EAGAIN;
+	}
+
+	npcm_i2c_init_params(bus);
+	bus->dest_addr = slave_addr;
+	bus->msgs = msgs;
+	bus->msgs_num = num;
+	bus->cmd_err = 0;
+	bus->read_block_use = read_block;
+
+	reinit_completion(&bus->cmd_complete);
+	if (!npcm_i2c_master_start_xmit(bus, slave_addr, nwrite, nread,
+					write_data, read_data, read_PEC,
+					read_block))
+		ret = -EBUSY;
+
+	if (ret != -EBUSY) {
+		time_left = wait_for_completion_timeout(&bus->cmd_complete,
+							timeout);
+
+		if (time_left == 0) {
+			if (bus->timeout_cnt < ULLONG_MAX)
+				bus->timeout_cnt++;
+			if (bus->master_or_slave == I2C_MASTER) {
+				i2c_recover_bus(adap);
+				bus->cmd_err = -EIO;
+				bus->state = I2C_IDLE;
+			}
+		}
+	}
+	ret = bus->cmd_err;
+
+	/* if there was BER, check if need to recover the bus: */
+	if (bus->cmd_err == -EAGAIN)
+		ret = i2c_recover_bus(adap);
+
+	return bus->cmd_err;
+}
+
+static u32 npcm_i2c_functionality(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C |
+	       I2C_FUNC_SMBUS_EMUL |
+	       I2C_FUNC_SMBUS_BLOCK_DATA |
+	       I2C_FUNC_SMBUS_PEC;
+}
+
+static const struct i2c_adapter_quirks npcm_i2c_quirks = {
+	.max_read_len = 32768,
+	.max_write_len = 32768,
+	.flags = I2C_AQ_COMB_WRITE_THEN_READ,
+};
+
+static const struct i2c_algorithm npcm_i2c_algo = {
+	.master_xfer = npcm_i2c_master_xfer,
+	.functionality = npcm_i2c_functionality,
+};
+
+/* i2c debugfs directory: used to keep health monitor of i2c devices */
+static struct dentry *npcm_i2c_debugfs_dir;
+
+static void npcm_i2c_init_debugfs(struct platform_device *pdev,
+				  struct npcm_i2c *bus)
+{
+	struct dentry *d;
+
+	if (!npcm_i2c_debugfs_dir)
+		return;
+	d = debugfs_create_dir(dev_name(&pdev->dev), npcm_i2c_debugfs_dir);
+	if (IS_ERR_OR_NULL(d))
+		return;
+	debugfs_create_u64("ber_cnt", 0444, d, &bus->ber_cnt);
+	debugfs_create_u64("nack_cnt", 0444, d, &bus->nack_cnt);
+	debugfs_create_u64("rec_succ_cnt", 0444, d, &bus->rec_succ_cnt);
+	debugfs_create_u64("rec_fail_cnt", 0444, d, &bus->rec_fail_cnt);
+	debugfs_create_u64("timeout_cnt", 0444, d, &bus->timeout_cnt);
+
+	bus->debugfs = d;
+}
+
+static int npcm_i2c_probe_bus(struct platform_device *pdev)
+{
+	struct npcm_i2c *bus;
+	struct i2c_adapter *adap;
+	struct clk *i2c_clk;
+	static struct regmap *gcr_regmap;
+	static struct regmap *clk_regmap;
+	int irq;
+	int ret;
+
+	bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
+	if (!bus)
+		return -ENOMEM;
+
+	bus->dev = &pdev->dev;
+
+	bus->num = of_alias_get_id(pdev->dev.of_node, "i2c");
+	/* core clk must be acquired to calculate module timing settings */
+	i2c_clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(i2c_clk))
+		return PTR_ERR(i2c_clk);
+	bus->apb_clk = clk_get_rate(i2c_clk);
+
+	gcr_regmap = syscon_regmap_lookup_by_compatible("nuvoton,npcm750-gcr");
+	if (IS_ERR(gcr_regmap))
+		return IS_ERR(gcr_regmap);
+	regmap_write(gcr_regmap, NPCM_I2CSEGCTL, NPCM_I2CSEGCTL_INIT_VAL);
+
+	clk_regmap = syscon_regmap_lookup_by_compatible("nuvoton,npcm750-clk");
+	if (IS_ERR(clk_regmap))
+		return IS_ERR(clk_regmap);
+
+	bus->reg = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(bus->reg))
+		return PTR_ERR((bus)->reg);
+
+	spin_lock_init(&bus->lock);
+	init_completion(&bus->cmd_complete);
+
+	adap = &bus->adap;
+	adap->owner = THIS_MODULE;
+	adap->retries = 3;
+	adap->timeout = HZ;
+	adap->algo = &npcm_i2c_algo;
+	adap->quirks = &npcm_i2c_quirks;
+	adap->algo_data = bus;
+	adap->dev.parent = &pdev->dev;
+	adap->dev.of_node = pdev->dev.of_node;
+	adap->nr = pdev->id;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	ret = devm_request_irq(bus->dev, irq, npcm_i2c_bus_irq, 0,
+			       dev_name(bus->dev), bus);
+	if (ret)
+		return ret;
+
+	ret = __npcm_i2c_init(bus, pdev);
+	if (ret)
+		return ret;
+
+	npcm_i2c_recovery_init(adap);
+
+	i2c_set_adapdata(adap, bus);
+
+	snprintf(bus->adap.name, sizeof(bus->adap.name), "npcm_i2c_%d",
+		 bus->num);
+	ret = i2c_add_numbered_adapter(&bus->adap);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, bus);
+	npcm_i2c_init_debugfs(pdev, bus);
+	return 0;
+}
+
+static int npcm_i2c_remove_bus(struct platform_device *pdev)
+{
+	unsigned long lock_flags;
+	struct npcm_i2c *bus = platform_get_drvdata(pdev);
+
+	debugfs_remove_recursive(bus->debugfs);
+	spin_lock_irqsave(&bus->lock, lock_flags);
+	npcm_i2c_disable(bus);
+	spin_unlock_irqrestore(&bus->lock, lock_flags);
+	i2c_del_adapter(&bus->adap);
+	return 0;
+}
+
+static const struct of_device_id npcm_i2c_bus_of_table[] = {
+	{ .compatible = "nuvoton,npcm750-i2c", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, npcm_i2c_bus_of_table);
+
+static struct platform_driver npcm_i2c_bus_driver = {
+	.probe = npcm_i2c_probe_bus,
+	.remove = npcm_i2c_remove_bus,
+	.driver = {
+		.name = "nuvoton-i2c",
+		.of_match_table = npcm_i2c_bus_of_table,
+	}
+};
+
+static int __init npcm_i2c_init(void)
+{
+	npcm_i2c_debugfs_dir = debugfs_create_dir("npcm_i2c", NULL);
+	platform_driver_register(&npcm_i2c_bus_driver);
+	return 0;
+}
+module_init(npcm_i2c_init);
+
+static void __exit npcm_i2c_exit(void)
+{
+	platform_driver_unregister(&npcm_i2c_bus_driver);
+	debugfs_remove_recursive(npcm_i2c_debugfs_dir);
+}
+module_exit(npcm_i2c_exit);
+
+MODULE_AUTHOR("Avi Fishman <avi.fishman@gmail.com>");
+MODULE_AUTHOR("Tali Perry <tali.perry@nuvoton.com>");
+MODULE_AUTHOR("Tyrone Ting <kfting@nuvoton.com>");
+MODULE_DESCRIPTION("Nuvoton I2C Bus Driver");
+MODULE_LICENSE("GPL v2");