[v7,2/2] i2c: npcm: Add Nuvoton NPCM I2C controller driver
diff mbox series

Message ID 20191121095350.158689-3-tali.perry1@gmail.com
State New
Headers show
Series
  • i2c: npcm: add NPCM i2c controller driver
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Commit Message

Tali Perry Nov. 21, 2019, 9:53 a.m. UTC
Add Nuvoton NPCM BMC i2c controller driver.

Signed-off-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/Kconfig       |   11 +
 drivers/i2c/busses/Makefile      |    1 +
 drivers/i2c/busses/i2c-npcm7xx.c | 2485 ++++++++++++++++++++++++++++++
 3 files changed, 2497 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-npcm7xx.c

Comments

Wolfram Sang Nov. 25, 2019, 3:16 p.m. UTC | #1
On Thu, Nov 21, 2019 at 11:53:50AM +0200, Tali Perry wrote:
> Add Nuvoton NPCM BMC i2c controller driver.
> 
> Signed-off-by: Tali Perry <tali.perry1@gmail.com>

Looking at all this SMB_* naming of the registers and also the quirks,
this looks more like an SMBUS controller to me?

> +	// currently I2C slave IF only supports single byte operations.
> +	// in order to utilyze the npcm HW FIFO, the driver will ask for 16bytes
> +	// at a time, pack them in buffer, and then transmit them all together
> +	// to the FIFO and onward to the bus .
> +	// NACK on read will be once reached to bus->adap->quirks->max_read_len
> +	// sending a NACK whever the backend requests for it is not supported.

This for example...

> +static const struct i2c_adapter_quirks npcm_i2c_quirks = {
> +	.max_read_len = 32768,
> +	.max_write_len = 32768,
> +	.max_num_msgs = 2,
> +	.flags = I2C_AQ_COMB_WRITE_THEN_READ
> +};

... and this. Like SMBus with the only exception of being able to send
32K in a row. Or?
Tali Perry Nov. 26, 2019, 9:27 a.m. UTC | #2
Hi Wolfram,

Thanks for your comments.

The NPCM7XX BMC I2C\SMB controller HW module supports both SMB and I2C.
It's main features are:
1. Supports Fast-Mode (400 KHz clock) I2C and Fast-Mode-plus (1 MHz clock) I2C
2. Supports the ‘fairness’ arbitration protocol defined by the MCTP
SMBus/I2C Transport Binding Specification v1.0.0
3. 32KB packets : this is an I2C spec limitation. The HW has no limit
on packets size. It has a 16 bytes FIFO which can be reloaded over and
over.
4. w\o size byte (for SMB block protocol).
5. Both master and slave. It can also replace modes in run time
(requirement for IPMB and MCTP).
6. Bus timing is selected to support both specs.

Originally the HW spec stated SMB everywhere .

Should I rename the SMB to I2C all over the driver?

Thanks,
Tali Perry


On Tue, Nov 26, 2019 at 8:47 AM Tali Perry <tali.perry1@gmail.com> wrote:
>
> Hi Wolfram,
>
> Thanks for your comments.
>
> The NPCM7XX BMC I2C\SMB controller HW module supports both SMB and I2C.
> It's main features are:
> 1. Supports Fast-Mode (400 KHz clock) I2C and Fast-Mode-plus (1 MHz clock) I2C
> 2. Supports the ‘fairness’ arbitration protocol defined by the MCTP SMBus/I2C Transport Binding Specification v1.0.0
> 3. 32KB packets : this is an I2C spec limitation. The HW has no limit on packets size. It has a 16 bytes FIFO which can be reloaded over and over.
> 4. w\o size byte (for SMB block protocol).
> 5. Both master and slave. It can also replace modes in run time (requirement for IPMB and MCTP).
> 6. Bus timing is selected to support both specs.
>
> Originally the HW spec stated SMB everywhere .
>
> Should I rename the SMB to I2C all over the driver?
>
> Thanks,
> Tali Perry
>
>
> On Mon, Nov 25, 2019 at 5:16 PM Wolfram Sang <wsa@the-dreams.de> wrote:
>>
>> On Thu, Nov 21, 2019 at 11:53:50AM +0200, Tali Perry wrote:
>> > Add Nuvoton NPCM BMC i2c controller driver.
>> >
>> > Signed-off-by: Tali Perry <tali.perry1@gmail.com>
>>
>> Looking at all this SMB_* naming of the registers and also the quirks,
>> this looks more like an SMBUS controller to me?
>>
>> > +     // currently I2C slave IF only supports single byte operations.
>> > +     // in order to utilyze the npcm HW FIFO, the driver will ask for 16bytes
>> > +     // at a time, pack them in buffer, and then transmit them all together
>> > +     // to the FIFO and onward to the bus .
>> > +     // NACK on read will be once reached to bus->adap->quirks->max_read_len
>> > +     // sending a NACK whever the backend requests for it is not supported.
>>
>> This for example...
>>
>> > +static const struct i2c_adapter_quirks npcm_i2c_quirks = {
>> > +     .max_read_len = 32768,
>> > +     .max_write_len = 32768,
>> > +     .max_num_msgs = 2,
>> > +     .flags = I2C_AQ_COMB_WRITE_THEN_READ
>> > +};
>>
>> ... and this. Like SMBus with the only exception of being able to send
>> 32K in a row. Or?
>>

Patch
diff mbox series

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 146ce40d8e0a..9091b93aaf90 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -786,6 +786,17 @@  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
+	select I2C_SLAVE
+	help
+	  If you say yes to this option, support will be included for the
+	  Nuvoton I2C controller.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-npcm7xx.
+
 config I2C_OCORES
 	tristate "OpenCores I2C Controller"
 	help
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 3ab8aebc39c9..4af59a806f3c 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -81,6 +81,7 @@  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..ce9699d56835
--- /dev/null
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -0,0 +1,2485 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NPCM7xx SMB Controller driver
+ *
+ * Copyright (C) 2018 Nuvoton Technologies tali.perry@nuvoton.com
+ */
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/irq.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>
+#include <linux/jiffies.h>
+
+#define I2C_VERSION "0.1.0"
+
+enum smb_mode {
+	SMB_SLAVE = 1,
+	SMB_MASTER
+};
+
+/*
+ * External SMB Interface driver xfer indication values, which indicate status
+ * of the bus.
+ */
+enum smb_state_ind {
+	SMB_NO_STATUS_IND = 0,
+	SMB_SLAVE_RCV_IND = 1,
+	SMB_SLAVE_XMIT_IND = 2,
+	SMB_SLAVE_XMIT_MISSING_DATA_IND = 3,
+	SMB_SLAVE_RESTART_IND = 4,
+	SMB_SLAVE_DONE_IND = 5,
+	SMB_MASTER_DONE_IND = 6,
+	SMB_NACK_IND = 8,
+	SMB_BUS_ERR_IND = 9,
+	SMB_WAKE_UP_IND = 10,
+	SMB_BLOCK_BYTES_ERR_IND = 12,
+	SMB_SLAVE_RCV_MISSING_DATA_IND = 14,
+};
+
+// SMBus Operation type values
+enum smb_oper {
+	SMB_NO_OPER = 0,
+	SMB_WRITE_OPER = 1,
+	SMB_READ_OPER = 2
+};
+
+// SMBus Bank (FIFO mode)
+enum smb_bank {
+	SMB_BANK_0 = 0,
+	SMB_BANK_1 = 1
+};
+
+// Internal SMB states values (for the SMB module state machine).
+enum smb_state {
+	SMB_DISABLE = 0,
+	SMB_IDLE,
+	SMB_MASTER_START,
+	SMB_SLAVE_MATCH,
+	SMB_OPER_STARTED,
+	SMB_STOP_PENDING
+};
+
+// Module supports setting multiple own slave addresses
+enum smb_addr {
+	SMB_SLAVE_ADDR1 = 0,
+	SMB_SLAVE_ADDR2,
+	SMB_SLAVE_ADDR3,
+	SMB_SLAVE_ADDR4,
+	SMB_SLAVE_ADDR5,
+	SMB_SLAVE_ADDR6,
+	SMB_SLAVE_ADDR7,
+	SMB_SLAVE_ADDR8,
+	SMB_SLAVE_ADDR9,
+	SMB_SLAVE_ADDR10,
+	SMB_GC_ADDR,
+	SMB_ARP_ADDR
+};
+
+// global regs
+static struct regmap *gcr_regmap;
+static struct regmap *clk_regmap;
+
+#define NPCM_I2CSEGCTL  0xE4
+#define I2CSEGCTL_VAL	0x0333F000
+
+// Common regs
+#define NPCM_SMBSDA			0x000
+#define NPCM_SMBST			0x002
+#define NPCM_SMBCST			0x004
+#define NPCM_SMBCTL1			0x006
+#define NPCM_SMBADDR1			0x008
+#define NPCM_SMBCTL2			0x00A
+#define NPCM_SMBADDR2			0x00C
+#define NPCM_SMBCTL3			0x00E
+#define NPCM_SMBCST2			0x018
+#define NPCM_SMBCST3			0x019
+#define SMB_VER				0x01F
+
+// BANK 0 regs
+#define NPCM_SMBADDR3			0x010
+#define NPCM_SMBADDR7			0x011
+#define NPCM_SMBADDR4			0x012
+#define NPCM_SMBADDR8			0x013
+#define NPCM_SMBADDR5			0x014
+#define NPCM_SMBADDR9			0x015
+#define NPCM_SMBADDR6			0x016
+#define NPCM_SMBADDR10			0x017
+
+// SMBADDR array: because the addr regs are sprinkled all over the address space
+const int  NPCM_SMBADDR[10] = {NPCM_SMBADDR1, NPCM_SMBADDR2, NPCM_SMBADDR3,
+			       NPCM_SMBADDR4, NPCM_SMBADDR5, NPCM_SMBADDR6,
+			       NPCM_SMBADDR7, NPCM_SMBADDR8, NPCM_SMBADDR9,
+			       NPCM_SMBADDR10};
+
+#define NPCM_SMBCTL4			0x01A
+#define NPCM_SMBCTL5			0x01B
+#define NPCM_SMBSCLLT			0x01C // SCL Low Time
+#define NPCM_SMBFIF_CTL			0x01D // FIFO Control
+#define NPCM_SMBSCLHT			0x01E // SCL High Time
+
+// BANK 1 regs
+#define NPCM_SMBFIF_CTS			0x010 // Both FIFOs Control and status
+#define NPCM_SMBTXF_CTL			0x012 // Tx-FIFO Control
+#define NPCM_SMBT_OUT			0x014 // Bus T.O.
+#define NPCM_SMBPEC			0x016 // PEC Data
+#define NPCM_SMBTXF_STS			0x01A // Tx-FIFO Status
+#define NPCM_SMBRXF_STS			0x01C // Rx-FIFO Status
+#define NPCM_SMBRXF_CTL			0x01E // Rx-FIFO Control
+
+// NPCM_SMBST reg fields
+#define NPCM_SMBST_XMIT			BIT(0)
+#define NPCM_SMBST_MASTER		BIT(1)
+#define NPCM_SMBST_NMATCH		BIT(2)
+#define NPCM_SMBST_STASTR		BIT(3)
+#define NPCM_SMBST_NEGACK		BIT(4)
+#define NPCM_SMBST_BER			BIT(5)
+#define NPCM_SMBST_SDAST		BIT(6)
+#define NPCM_SMBST_SLVSTP		BIT(7)
+
+// NPCM_SMBCST reg fields
+#define NPCM_SMBCST_BUSY		BIT(0)
+#define NPCM_SMBCST_BB			BIT(1)
+#define NPCM_SMBCST_MATCH		BIT(2)
+#define NPCM_SMBCST_GCMATCH		BIT(3)
+#define NPCM_SMBCST_TSDA		BIT(4)
+#define NPCM_SMBCST_TGSCL		BIT(5)
+#define NPCM_SMBCST_MATCHAF		BIT(6)
+#define NPCM_SMBCST_ARPMATCH		BIT(7)
+
+// NPCM_SMBCTL1 reg fields
+#define NPCM_SMBCTL1_START		BIT(0)
+#define NPCM_SMBCTL1_STOP		BIT(1)
+#define NPCM_SMBCTL1_INTEN		BIT(2)
+#define NPCM_SMBCTL1_EOBINTE		BIT(3)
+#define NPCM_SMBCTL1_ACK		BIT(4)
+#define NPCM_SMBCTL1_GCMEN		BIT(5)
+#define NPCM_SMBCTL1_NMINTE		BIT(6)
+#define NPCM_SMBCTL1_STASTRE		BIT(7)
+
+// RW1S fields (inside a RW reg):
+#define NPCM_SMBCTL1_RWS_FIELDS	  (NPCM_SMBCTL1_START | NPCM_SMBCTL1_STOP | \
+				   NPCM_SMBCTL1_ACK)
+// NPCM_SMBADDR reg fields
+#define NPCM_SMBADDR_A			GENMASK(6, 0)
+#define NPCM_SMBADDR_SAEN		BIT(7)
+
+// NPCM_SMBCTL2 reg fields
+#define SMBCTL2_ENABLE			BIT(0)
+#define SMBCTL2_SCLFRQ6_0		GENMASK(7, 1)
+
+// NPCM_SMBCTL3 reg fields
+#define SMBCTL3_SCLFRQ8_7		GENMASK(1, 0)
+#define SMBCTL3_ARPMEN			BIT(2)
+#define SMBCTL3_IDL_START		BIT(3)
+#define SMBCTL3_400K_MODE		BIT(4)
+#define SMBCTL3_BNK_SEL			BIT(5)
+#define SMBCTL3_SDA_LVL			BIT(6)
+#define SMBCTL3_SCL_LVL			BIT(7)
+
+// NPCM_SMBCST2 reg fields
+#define NPCM_SMBCST2_MATCHA1F		BIT(0)
+#define NPCM_SMBCST2_MATCHA2F		BIT(1)
+#define NPCM_SMBCST2_MATCHA3F		BIT(2)
+#define NPCM_SMBCST2_MATCHA4F		BIT(3)
+#define NPCM_SMBCST2_MATCHA5F		BIT(4)
+#define NPCM_SMBCST2_MATCHA6F		BIT(5)
+#define NPCM_SMBCST2_MATCHA7F		BIT(5)
+#define NPCM_SMBCST2_INTSTS		BIT(7)
+
+// NPCM_SMBCST3 reg fields
+#define NPCM_SMBCST3_MATCHA8F		BIT(0)
+#define NPCM_SMBCST3_MATCHA9F		BIT(1)
+#define NPCM_SMBCST3_MATCHA10F		BIT(2)
+#define NPCM_SMBCST3_EO_BUSY		BIT(7)
+
+// NPCM_SMBCTL4 reg fields
+#define SMBCTL4_HLDT			GENMASK(5, 0)
+#define SMBCTL4_LVL_WE			BIT(7)
+
+// NPCM_SMBCTL5 reg fields
+#define SMBCTL5_DBNCT			GENMASK(3, 0)
+
+// NPCM_SMBFIF_CTS reg fields
+#define NPCM_SMBFIF_CTS_RXF_TXE		BIT(1)
+#define NPCM_SMBFIF_CTS_RFTE_IE		BIT(3)
+#define NPCM_SMBFIF_CTS_CLR_FIFO	BIT(6)
+#define NPCM_SMBFIF_CTS_SLVRSTR		BIT(7)
+
+// NPCM_SMBTXF_CTL reg fields
+#define NPCM_SMBTXF_CTL_TX_THR		GENMASK(4, 0)
+#define NPCM_SMBTXF_CTL_THR_TXIE	BIT(6)
+
+// NPCM_SMBT_OUT reg fields
+#define NPCM_SMBT_OUT_TO_CKDIV		GENMASK(5, 0)
+#define NPCM_SMBT_OUT_T_OUTIE		BIT(6)
+#define NPCM_SMBT_OUT_T_OUTST		BIT(7)
+
+// NPCM_SMBTXF_STS reg fields
+#define NPCM_SMBTXF_STS_TX_BYTES	GENMASK(4, 0)
+#define NPCM_SMBTXF_STS_TX_THST		BIT(6)
+
+// NPCM_SMBRXF_STS reg fields
+#define NPCM_SMBRXF_STS_RX_BYTES	GENMASK(4, 0)
+#define NPCM_SMBRXF_STS_RX_THST		BIT(6)
+
+// NPCM_SMBFIF_CTL reg fields
+#define NPCM_SMBFIF_CTL_FIFO_EN		BIT(4)
+
+// NPCM_SMBRXF_CTL reg fields
+#define NPCM_SMBRXF_CTL_RX_THR		GENMASK(4, 0)
+#define NPCM_SMBRXF_CTL_LAST_PEC	BIT(5)
+#define NPCM_SMBRXF_CTL_THR_RXIE	BIT(6)
+
+#define SMBUS_FIFO_SIZE			16
+
+// SMB_VER reg fields
+#define SMB_VER_VERSION			GENMASK(6, 0)
+#define SMB_VER_FIFO_EN			BIT(7)
+
+// stall/stuck timeout
+const unsigned int DEFAULT_STALL_COUNT =	25;
+
+// retries in a loop for master abort
+const unsigned int RETRIES_NUM =	10000;
+
+// SMBus spec. values in KHZ
+const unsigned int SMBUS_FREQ_MIN = 10;
+const unsigned int SMBUS_FREQ_MAX = 1000;
+const unsigned int SMBUS_FREQ_100KHZ = 100;
+const unsigned int SMBUS_FREQ_400KHZ = 400;
+const unsigned int SMBUS_FREQ_1MHZ = 1000;
+
+// SCLFRQ min/max field values
+const unsigned int SCLFRQ_MIN = 10;
+const unsigned int SCLFRQ_MAX = 511;
+
+// SCLFRQ field position
+#define SCLFRQ_0_TO_6		GENMASK(6, 0)
+#define SCLFRQ_7_TO_8		GENMASK(8, 7)
+
+const unsigned int SMB_NUM_OF_ADDR = 10;
+
+#define NPCM_I2C_EVENT_START	BIT(0)
+#define NPCM_I2C_EVENT_STOP	BIT(1)
+#define NPCM_I2C_EVENT_ABORT	BIT(2)
+#define NPCM_I2C_EVENT_WRITE	BIT(3)
+
+#define NPCM_I2C_EVENT_READ	BIT(4)
+#define NPCM_I2C_EVENT_BER	BIT(5)
+#define NPCM_I2C_EVENT_NACK	BIT(6)
+#define NPCM_I2C_EVENT_TO	BIT(7)
+
+#define NPCM_I2C_EVENT_EOB	BIT(8)
+#define NPCM_I2C_EVENT_STALL	BIT(9)
+#define NPCM_I2C_EVENT_CB	BIT(10)
+#define NPCM_I2C_EVENT_DONE	BIT(11)
+
+#define NPCM_I2C_EVENT_READ1	BIT(12)
+#define NPCM_I2C_EVENT_READ2	BIT(13)
+#define NPCM_I2C_EVENT_READ3	BIT(14)
+#define NPCM_I2C_EVENT_READ4	BIT(15)
+
+#define NPCM_I2C_EVENT_NMATCH_SLV	BIT(16)
+#define NPCM_I2C_EVENT_NMATCH_MSTR	BIT(17)
+#define NPCM_I2C_EVENT_BER_SLV		BIT(18)
+
+#define NPCM_I2C_EVENT_LOG(event)	(bus->event_log |= event)
+
+// Status of one SMBus 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			irq;
+	int			cmd_err;
+	struct i2c_msg		*msgs;
+	int			msgs_num;
+	int			num;
+	u32			apb_clk;
+	struct i2c_bus_recovery_info rinfo;
+	enum smb_state		state;
+	enum smb_oper		operation;
+	enum smb_mode		master_or_slave;
+	enum smb_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;
+
+	// PEC bit mask per slave address.
+	//		1: use PEC for this address,
+	//		0: do not use PEC for this address
+	u16			PEC_mask;
+	bool			PEC_use;
+	bool			read_block_use;
+	u8			int_cnt;
+	u32			event_log;
+	u32			event_log_prev;
+	u32			clk_period_us;
+	unsigned long		int_time_stamp;
+	unsigned long		bus_freq; // in kHz
+	u32			xmits;
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+	u8			own_slave_addr;
+	struct i2c_client	*slave;
+
+	// currently I2C slave IF only supports single byte operations.
+	// in order to utilyze the npcm HW FIFO, the driver will ask for 16bytes
+	// at a time, pack them in buffer, and then transmit them all together
+	// to the FIFO and onward to the bus .
+	// NACK on read will be once reached to bus->adap->quirks->max_read_len
+	// sending a NACK whever the backend requests for it is not supported.
+
+	// This module can be master and slave at the same time. separate ptrs
+	// and counters:
+	int			slv_rd_size;
+	int			slv_rd_ind;
+	int			slv_wr_size;
+	int			slv_wr_ind;
+	u8			slv_rd_buf[SMBUS_FIFO_SIZE];
+	u8			slv_wr_buf[SMBUS_FIFO_SIZE];
+#endif
+};
+
+static inline void npcm_smb_select_bank(struct npcm_i2c *bus,
+					enum smb_bank bank)
+{
+	if (bank == SMB_BANK_0)
+		iowrite8(ioread8(bus->reg + NPCM_SMBCTL3) & ~SMBCTL3_BNK_SEL,
+			 bus->reg + NPCM_SMBCTL3);
+	else
+		iowrite8(ioread8(bus->reg + NPCM_SMBCTL3) | SMBCTL3_BNK_SEL,
+			 bus->reg + NPCM_SMBCTL3);
+}
+
+static void npcm_smb_init_params(struct npcm_i2c *bus)
+{
+	bus->stop_ind = SMB_NO_STATUS_IND;
+	bus->rd_size = 0;
+	bus->wr_size = 0;
+	bus->rd_ind = 0;
+	bus->wr_ind = 0;
+	bus->int_cnt = 0;
+	bus->event_log_prev = bus->event_log;
+	bus->event_log = 0;
+	bus->read_block_use = false;
+	bus->int_time_stamp = 0;
+	bus->PEC_use = false;
+	bus->PEC_mask = 0;
+	if (bus->slave)
+		bus->master_or_slave = SMB_SLAVE;
+}
+
+static inline void npcm_smb_wr_byte(struct npcm_i2c *bus, u8 data)
+{
+	iowrite8(data, bus->reg + NPCM_SMBSDA);
+}
+
+static inline void npcm_smb_rd_byte(struct npcm_i2c *bus, u8 *data)
+{
+	*data = ioread8(bus->reg + NPCM_SMBSDA);
+}
+
+static inline u16 npcm_smb_get_index(struct npcm_i2c *bus)
+{
+	u16 index = 0;
+
+	if (bus->operation == SMB_READ_OPER)
+		index = bus->rd_ind;
+	else if (bus->operation == SMB_WRITE_OPER)
+		index = bus->wr_ind;
+
+	return index;
+}
+
+// quick protocol (just address):
+static inline bool npcm_smb_is_quick(struct npcm_i2c *bus)
+{
+	if (bus->wr_size == 0 && bus->rd_size == 0)
+		return true;
+	return false;
+}
+
+static void npcm_smb_disable(struct npcm_i2c *bus)
+{
+	int i;
+
+	// select bank 0 for SMB addresses
+	npcm_smb_select_bank(bus, SMB_BANK_0);
+
+	// Slave addresses removal
+	for (i = SMB_SLAVE_ADDR1; i < SMB_NUM_OF_ADDR; i++)
+		iowrite8(0, bus->reg + NPCM_SMBADDR[i]);
+
+	npcm_smb_select_bank(bus, SMB_BANK_1);
+
+	// Disable module.
+	iowrite8(ioread8(bus->reg + NPCM_SMBCTL2) & ~SMBCTL2_ENABLE,
+		 bus->reg + NPCM_SMBCTL2);
+
+	bus->state = SMB_DISABLE;
+}
+
+static void npcm_smb_enable(struct npcm_i2c *bus)
+{
+	iowrite8((ioread8(bus->reg + NPCM_SMBCTL2) | SMBCTL2_ENABLE),
+		 bus->reg + NPCM_SMBCTL2);
+
+	bus->state = SMB_IDLE;
+}
+
+static bool npcm_smb_wait_for_bus_free(struct npcm_i2c *bus, bool may_sleep)
+{
+	int cnt = 0;
+	int max_count = 2; /* wait for 2 ms */
+
+	if (may_sleep)
+		might_sleep();
+	else
+		max_count = max_count * 100; /* since each delay is 10 us */
+
+	while  (ioread8(bus->reg + NPCM_SMBCST) & NPCM_SMBCST_BUSY) {
+		if (cnt < max_count) {
+			if (may_sleep)
+				msleep_interruptible(1);
+			else
+				udelay(10);
+			cnt++;
+
+		} else {
+			bus->cmd_err = -EAGAIN;
+			return false;
+		}
+	}
+	return true;
+}
+
+// enable\disable end of busy (EOB) interrupt
+static inline void npcm_smb_eob_int(struct npcm_i2c *bus, bool enable)
+{
+	// Clear EO_BUSY pending bit:
+	iowrite8(ioread8(bus->reg + NPCM_SMBCST3) | NPCM_SMBCST3_EO_BUSY,
+		 bus->reg + NPCM_SMBCST3);
+
+	if (enable) {
+		iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) |
+			 NPCM_SMBCTL1_EOBINTE)  & ~NPCM_SMBCTL1_RWS_FIELDS,
+			 bus->reg + NPCM_SMBCTL1);
+	} else {
+		iowrite8(ioread8(bus->reg + NPCM_SMBCTL1) &
+			 ~NPCM_SMBCTL1_EOBINTE & ~NPCM_SMBCTL1_RWS_FIELDS,
+			 bus->reg + NPCM_SMBCTL1);
+	}
+}
+
+static inline bool npcm_smb_tx_fifo_empty(struct npcm_i2c *bus)
+{
+	u8 tx_fifo_sts = ioread8(bus->reg + NPCM_SMBTXF_STS);
+
+	// check if TX FIFO is not empty
+	if ((tx_fifo_sts & NPCM_SMBTXF_STS_TX_BYTES) == 0)
+		return false;
+
+	// check if TX FIFO status bit is set:
+	return (bool)FIELD_GET(NPCM_SMBTXF_STS_TX_THST, tx_fifo_sts);
+}
+
+static inline bool npcm_smb_rx_fifo_full(struct npcm_i2c *bus)
+{
+	u8 rx_fifo_sts = ioread8(bus->reg + NPCM_SMBRXF_STS);
+
+	// check if RX FIFO is not empty:
+	if ((rx_fifo_sts & NPCM_SMBRXF_STS_RX_BYTES) == 0)
+		return false;
+
+	// check if rx fifo full status is set:
+	return (bool)FIELD_GET(NPCM_SMBRXF_STS_RX_THST, rx_fifo_sts);
+}
+
+static inline void npcm_smb_clear_fifo_int(struct npcm_i2c *bus)
+{
+	iowrite8((ioread8(bus->reg + NPCM_SMBFIF_CTS) &
+			NPCM_SMBFIF_CTS_SLVRSTR) |
+			NPCM_SMBFIF_CTS_RXF_TXE,
+			bus->reg + NPCM_SMBFIF_CTS);
+}
+
+static inline void npcm_smb_clear_tx_fifo(struct npcm_i2c *bus)
+{
+	iowrite8(ioread8(bus->reg + NPCM_SMBTXF_STS) | NPCM_SMBTXF_STS_TX_THST,
+		 bus->reg + NPCM_SMBTXF_STS);
+}
+
+static inline void npcm_smb_clear_rx_fifo(struct npcm_i2c *bus)
+{
+	iowrite8(ioread8(bus->reg + NPCM_SMBRXF_STS) | NPCM_SMBRXF_STS_RX_THST,
+		 bus->reg + NPCM_SMBRXF_STS);
+}
+
+static void npcm_smb_int_enable(struct npcm_i2c *bus, bool enable)
+{
+	if (enable)
+		iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) |
+			 NPCM_SMBCTL1_INTEN) & ~NPCM_SMBCTL1_RWS_FIELDS,
+			 bus->reg + NPCM_SMBCTL1);
+	else
+		iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) &
+			 ~NPCM_SMBCTL1_INTEN) & ~NPCM_SMBCTL1_RWS_FIELDS,
+			 bus->reg + NPCM_SMBCTL1);
+}
+
+static inline void npcm_smb_master_start(struct npcm_i2c *bus)
+{
+	NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_START);
+
+	iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) | NPCM_SMBCTL1_START) &
+		 ~(NPCM_SMBCTL1_STOP | NPCM_SMBCTL1_ACK),
+		 bus->reg + NPCM_SMBCTL1);
+}
+
+static inline void npcm_smb_master_stop(struct npcm_i2c *bus)
+{
+	NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_STOP);
+
+	// override HW issue: SMBus 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);
+
+	iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) | NPCM_SMBCTL1_STOP) &
+		 ~(NPCM_SMBCTL1_START | NPCM_SMBCTL1_ACK),
+		 bus->reg + NPCM_SMBCTL1);
+
+	if (bus->fifo_use) {
+		npcm_smb_select_bank(bus, SMB_BANK_1);
+
+		if (bus->operation == SMB_READ_OPER)
+			npcm_smb_clear_rx_fifo(bus);
+		else
+			npcm_smb_clear_tx_fifo(bus);
+
+		npcm_smb_clear_fifo_int(bus);
+
+		iowrite8(0, bus->reg + NPCM_SMBTXF_CTL);
+	}
+}
+
+static inline void npcm_smb_stall_after_start(struct npcm_i2c *bus, bool stall)
+{
+	if (stall)
+		iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) |
+			 NPCM_SMBCTL1_STASTRE)  & ~NPCM_SMBCTL1_RWS_FIELDS,
+			 bus->reg + NPCM_SMBCTL1);
+	else
+		iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) &
+			 ~NPCM_SMBCTL1_STASTRE)  & ~NPCM_SMBCTL1_RWS_FIELDS,
+			 bus->reg + NPCM_SMBCTL1);
+}
+
+static inline void npcm_smb_nack(struct npcm_i2c *bus)
+{
+	iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) | NPCM_SMBCTL1_ACK) &
+		 ~(NPCM_SMBCTL1_STOP | NPCM_SMBCTL1_START),
+		 bus->reg + NPCM_SMBCTL1);
+}
+
+static int  npcm_smb_slave_enable_l(struct npcm_i2c *bus,
+				    enum smb_addr addr_type, u8 addr,
+				    bool enable);
+
+static void npcm_smb_reset(struct npcm_i2c *bus)
+{
+	// Save NPCM_SMBCTL1 relevant bits. It is being cleared when the
+	// module is disabled
+	u8 smbctl1;
+
+	smbctl1 = ioread8(bus->reg + NPCM_SMBCTL1);
+
+	// Disable the SMB module
+	iowrite8((ioread8(bus->reg + NPCM_SMBCTL2) & ~SMBCTL2_ENABLE),
+		 bus->reg + NPCM_SMBCTL2);
+
+	// Enable the SMB module
+	npcm_smb_enable(bus);
+
+	// Restore NPCM_SMBCTL1 status
+	iowrite8(smbctl1 & ~NPCM_SMBCTL1_RWS_FIELDS, bus->reg + NPCM_SMBCTL1);
+
+	// Clear BB (BUS BUSY) bit
+	iowrite8(NPCM_SMBCST_BB, bus->reg + NPCM_SMBCST);
+
+	iowrite8(0xFF, bus->reg + NPCM_SMBST);
+
+	// Clear EOB bit
+	iowrite8(NPCM_SMBCST3_EO_BUSY, bus->reg + NPCM_SMBCST3);
+
+	// Clear all fifo bits:
+	iowrite8(NPCM_SMBFIF_CTS_CLR_FIFO, bus->reg + NPCM_SMBFIF_CTS);
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+	if (bus->slave) {
+		npcm_smb_slave_enable_l(bus, SMB_SLAVE_ADDR1, bus->slave->addr,
+					true);
+	}
+#endif
+
+	bus->state = SMB_IDLE;
+}
+
+static inline bool npcm_smb_is_master(struct npcm_i2c *bus)
+{
+	return (bool)FIELD_GET(NPCM_SMBST_MASTER,
+			       ioread8(bus->reg + NPCM_SMBST));
+}
+
+static void npcm_smb_callback(struct npcm_i2c *bus,
+			      enum smb_state_ind op_status, u16 info)
+{
+	struct i2c_msg *msgs = bus->msgs;
+	int msgs_num = bus->msgs_num;
+
+	NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_CB);
+
+	if (!msgs)
+		return;
+
+	if (completion_done(&bus->cmd_complete) == true)
+		return;
+
+	switch (op_status) {
+	case SMB_MASTER_DONE_IND:
+		bus->cmd_err = bus->msgs_num;
+		// fall through:
+	case SMB_BLOCK_BYTES_ERR_IND:
+		// Master transaction 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;
+		}
+
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_DONE);
+
+		if (completion_done(&bus->cmd_complete) == false)
+			complete(&bus->cmd_complete);
+	break;
+
+	case SMB_NACK_IND:
+		// MASTER transmit got a NACK before tx all bytes
+		// info: number of transmitted bytes
+		bus->cmd_err = -ENXIO;
+		if (bus->master_or_slave == SMB_MASTER)
+			complete(&bus->cmd_complete);
+
+		break;
+	case SMB_BUS_ERR_IND:
+		// Bus error
+		bus->cmd_err = -EAGAIN;
+		if (bus->master_or_slave == SMB_MASTER)
+			complete(&bus->cmd_complete);
+
+		break;
+	case SMB_WAKE_UP_IND:
+		// SMBus wake up
+		break;
+	default:
+		break;
+	}
+
+	bus->operation = SMB_NO_OPER;
+	if (bus->slave)
+		bus->master_or_slave = SMB_SLAVE;
+}
+
+static u32 npcm_smb_get_fifo_fullness(struct npcm_i2c *bus)
+{
+	if (bus->operation == SMB_WRITE_OPER)
+		return FIELD_GET(NPCM_SMBTXF_STS_TX_BYTES,
+				 ioread8(bus->reg + NPCM_SMBTXF_STS));
+	else if (bus->operation == SMB_READ_OPER)
+		return FIELD_GET(NPCM_SMBRXF_STS_RX_BYTES,
+				 ioread8(bus->reg + NPCM_SMBRXF_STS));
+	return 0;
+}
+
+static void npcm_smb_write_to_fifo_master(struct npcm_i2c *bus,
+					  u16 max_bytes_to_send)
+{
+	// Fill the FIFO, while the FIFO is not full and there are more bytes to
+	// write
+	if (max_bytes_to_send == 0)
+		return;
+	while ((max_bytes_to_send--) && (SMBUS_FIFO_SIZE -
+					 npcm_smb_get_fifo_fullness(bus))) {
+		if (bus->wr_ind < bus->wr_size)
+			npcm_smb_wr_byte(bus, bus->wr_buf[bus->wr_ind++]);
+		else
+			npcm_smb_wr_byte(bus, 0xFF);
+	}
+}
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+static void npcm_smb_write_to_fifo_slave(struct npcm_i2c *bus,
+					 u16 max_bytes_to_send)
+{
+	// Fill the FIFO, while the FIFO is not full and there are more bytes to
+	// write
+	npcm_smb_clear_fifo_int(bus);
+	npcm_smb_clear_tx_fifo(bus);
+	iowrite8(0, bus->reg + NPCM_SMBTXF_CTL);
+
+	if (max_bytes_to_send == 0)
+		return;
+
+	while ((max_bytes_to_send--) && (SMBUS_FIFO_SIZE -
+					 npcm_smb_get_fifo_fullness(bus))) {
+		if (bus->slv_wr_size > 0) {
+			npcm_smb_wr_byte(bus,
+					 bus->slv_wr_buf[bus->slv_wr_ind %
+					 SMBUS_FIFO_SIZE]);
+			bus->slv_wr_ind = (bus->slv_wr_ind + 1) %
+					   SMBUS_FIFO_SIZE;
+			bus->slv_wr_size--; // size indicates the # of bytes in
+					    // the SW FIFO, not HW.
+		} else {
+			break;
+		}
+	}
+}
+#endif
+
+// configure the FIFO before using it. If nread is -1 RX FIFO will not be
+// configured. same for	nwrite
+static void npcm_smb_set_fifo(struct npcm_i2c *bus, int nread, int nwrite)
+{
+	u8 rxf_ctl = 0;
+
+	if (!bus->fifo_use)
+		return;
+	npcm_smb_select_bank(bus, SMB_BANK_1);
+	npcm_smb_clear_tx_fifo(bus);
+	npcm_smb_clear_rx_fifo(bus);
+
+	// configure RX FIFO
+	if (nread > 0) {
+		rxf_ctl = min_t(u16, (u16)nread, (u16)SMBUS_FIFO_SIZE);
+
+		// set LAST bit. if LAST is set enxt FIFO packet is nacked
+		// regular read of less then buffer size:
+		if (nread <= SMBUS_FIFO_SIZE)
+			rxf_ctl |= NPCM_SMBRXF_CTL_LAST_PEC;
+		// if we are about to read the first byte in blk rd mode,
+		// don't NACK it. BTW, if slave return 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_SMBRXF_CTL);
+	}
+
+	// configure TX FIFO
+	if (nwrite > 0) {
+		if (nwrite > SMBUS_FIFO_SIZE)
+			// data to send is more then FIFO size.
+			// Configure the FIFO int to be after of FIFO is cleared
+			iowrite8(SMBUS_FIFO_SIZE, bus->reg + NPCM_SMBTXF_CTL);
+		else
+			iowrite8(nwrite, bus->reg + NPCM_SMBTXF_CTL);
+
+		npcm_smb_clear_tx_fifo(bus);
+	}
+}
+
+static void npcm_smb_read_from_fifo(struct npcm_i2c *bus, u8 bytes_in_fifo)
+{
+	u8 data;
+
+	while (bytes_in_fifo--) {
+		npcm_smb_rd_byte(bus, &data);
+
+		if (bus->master_or_slave == SMB_MASTER) {
+			if (bus->rd_ind < bus->rd_size)
+				bus->rd_buf[bus->rd_ind++] = data;
+		} else { // SMB_SLAVE:
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+			if (bus->slave) {
+				bus->slv_rd_buf[bus->slv_rd_ind %
+						SMBUS_FIFO_SIZE] = data;
+				bus->slv_rd_ind++;
+				if (bus->slv_rd_ind == 1 && bus->read_block_use)
+					// 1st byte is length in block protocol
+					bus->slv_rd_size = data +
+							   (u8)bus->PEC_use +
+							(u8)bus->read_block_use;
+			}
+#endif
+		}
+	}
+}
+
+static int npcm_smb_master_abort(struct npcm_i2c *bus)
+{
+	int ret = 0;
+
+	NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_ABORT);
+
+	// Only current master is allowed to issue Stop Condition
+	if (npcm_smb_is_master(bus)) {
+		npcm_smb_eob_int(bus, true);
+		npcm_smb_master_stop(bus);
+
+		// Clear NEGACK, STASTR and BER bits
+		iowrite8(NPCM_SMBST_BER | NPCM_SMBST_NEGACK | NPCM_SMBST_STASTR,
+			 bus->reg + NPCM_SMBST);
+	}
+
+	return ret;
+}
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+static irqreturn_t npcm_i2c_bus_irq(int irq, void *dev_id);
+
+static int  npcm_smb_slave_enable_l(struct npcm_i2c *bus,
+				    enum smb_addr addr_type, u8 addr,
+				    bool enable)
+{
+	u8 slave_addr_reg = FIELD_PREP(NPCM_SMBADDR_A, addr) |
+		FIELD_PREP(NPCM_SMBADDR_SAEN, enable);
+
+	if (addr_type == SMB_GC_ADDR) {
+		iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) &
+			~NPCM_SMBCTL1_GCMEN) |
+			FIELD_PREP(NPCM_SMBCTL1_GCMEN, enable),
+			bus->reg + NPCM_SMBCTL1);
+		return 0;
+	}
+	if (addr_type == SMB_ARP_ADDR) {
+		iowrite8((ioread8(bus->reg + NPCM_SMBCTL3) &
+			~SMBCTL3_ARPMEN) |
+			FIELD_PREP(SMBCTL3_ARPMEN, enable),
+			bus->reg + NPCM_SMBCTL3);
+		return 0;
+	}
+	if (addr_type >= SMB_ARP_ADDR)
+		return -EFAULT;
+
+	// select bank 0 for address 3 to 10
+	if (addr_type > SMB_SLAVE_ADDR2)
+		npcm_smb_select_bank(bus, SMB_BANK_0);
+
+	// Set and enable the address
+	iowrite8(slave_addr_reg, bus->reg + NPCM_SMBADDR[(int)addr_type]);
+
+	// enable interrupt on slave match:
+	iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) | NPCM_SMBCTL1_NMINTE) &
+		 ~NPCM_SMBCTL1_RWS_FIELDS, bus->reg + NPCM_SMBCTL1);
+
+	if (addr_type > SMB_SLAVE_ADDR2)
+		npcm_smb_select_bank(bus, SMB_BANK_1);
+	return 0;
+}
+
+static u8 npcm_smb_get_slave_addr(struct npcm_i2c *bus,
+				  enum smb_addr addr_type)
+{
+	u8 slave_add;
+
+	// select bank 0 for address 3 to 10
+	if (addr_type > SMB_SLAVE_ADDR2)
+		npcm_smb_select_bank(bus, SMB_BANK_0);
+
+	slave_add = ioread8(bus->reg + NPCM_SMBADDR[(int)addr_type]);
+
+	if (addr_type > SMB_SLAVE_ADDR2)
+		npcm_smb_select_bank(bus, SMB_BANK_1);
+
+	return  slave_add;
+}
+
+static int  npcm_smb_remove_slave_addr(struct npcm_i2c *bus, u8 slave_add)
+{
+	int i;
+
+	slave_add |= 0x80; //Set the enable bit
+
+	npcm_smb_select_bank(bus, SMB_BANK_0);
+
+	for (i = SMB_SLAVE_ADDR1; i < SMB_NUM_OF_ADDR; i++) {
+		if (ioread8(bus->reg + NPCM_SMBADDR[i]) == slave_add)
+			iowrite8(0, bus->reg + NPCM_SMBADDR[i]);
+	}
+
+	npcm_smb_select_bank(bus, SMB_BANK_1);
+
+	return 0;
+}
+
+static int npcm_i2c_slave_get_wr_buf(struct npcm_i2c *bus)
+{
+	u8 value = 0;
+	int ret = bus->slv_wr_ind;
+	int i;
+
+	// fill a cyclic buffer
+	for (i = 0; i < SMBUS_FIFO_SIZE; i++) {
+		if (bus->slv_wr_size >= SMBUS_FIFO_SIZE)
+			break;
+		i2c_slave_event(bus->slave, I2C_SLAVE_READ_REQUESTED, &value);
+		bus->slv_wr_buf[(bus->slv_wr_ind + bus->slv_wr_size) %
+				 SMBUS_FIFO_SIZE] = value;
+		bus->slv_wr_size++;
+		i2c_slave_event(bus->slave, I2C_SLAVE_READ_PROCESSED, &value);
+	}
+	return SMBUS_FIFO_SIZE - ret;
+}
+
+static void npcm_i2c_slave_send_rd_buf(struct npcm_i2c *bus)
+{
+	int i;
+
+	for (i = 0; i < bus->slv_rd_ind; i++)
+		i2c_slave_event(bus->slave, I2C_SLAVE_WRITE_RECEIVED,
+				&bus->slv_rd_buf[i]);
+
+	// once we send bytes up, need to reset the counter of the wr buf
+	// got data from master (new offset in device), ignore wr fifo:
+	if (bus->slv_rd_ind) {
+		bus->slv_wr_size = 0;
+		bus->slv_wr_ind = 0;
+	}
+
+	bus->slv_rd_ind = 0;
+	bus->slv_rd_size = bus->adap.quirks->max_read_len;
+
+	npcm_smb_clear_fifo_int(bus);
+	npcm_smb_clear_rx_fifo(bus);
+}
+
+static bool npcm_smb_slave_receive(struct npcm_i2c *bus, u16 nread,
+				   u8 *read_data)
+{
+	bus->state = SMB_OPER_STARTED;
+	bus->operation	 = SMB_READ_OPER;
+	bus->slv_rd_size = nread;
+	bus->slv_rd_ind	= 0;
+
+	iowrite8(0, bus->reg + NPCM_SMBTXF_CTL);
+	iowrite8(SMBUS_FIFO_SIZE, bus->reg + NPCM_SMBRXF_CTL);
+
+	npcm_smb_clear_tx_fifo(bus);
+	npcm_smb_clear_rx_fifo(bus);
+
+	return true;
+}
+
+static bool npcm_smb_slave_xmit(struct npcm_i2c *bus, u16 nwrite,
+				u8 *write_data)
+{
+	if (nwrite == 0)
+		return false;
+
+	bus->state = SMB_OPER_STARTED;
+	bus->operation = SMB_WRITE_OPER;
+
+	// get the next buffer
+	npcm_i2c_slave_get_wr_buf(bus);
+
+	if (nwrite > 0)
+		npcm_smb_write_to_fifo_slave(bus, nwrite);
+
+	return true;
+}
+
+// currently slave IF only supports single byte operations.
+// in order to utilyze the npcm HW FIFO, the driver will ask for 16 bytes
+// at a time, pack them in buffer, and then transmit them all together
+// to the FIFO and onward to the bus.
+// NACK on read will be once reached to bus->adap->quirks->max_read_len.
+// sending a NACK wherever the backend requests for it is not supported.
+// the next two functions allow reading to local buffer before writing it all
+// to the HW FIFO.
+// ret val: number of bytes read form the IF:
+
+static int npcm_i2c_slave_wr_buf_sync(struct npcm_i2c *bus)
+{
+	int left_in_fifo = FIELD_GET(NPCM_SMBTXF_STS_TX_BYTES,
+			ioread8(bus->reg + NPCM_SMBTXF_STS));
+
+	if (left_in_fifo >= SMBUS_FIFO_SIZE)
+		return left_in_fifo;
+
+	if (bus->slv_wr_size >= SMBUS_FIFO_SIZE)
+		return left_in_fifo; // fifo already full
+
+	// update the wr fifo ind, back to the untransmitted bytes:
+	bus->slv_wr_ind = bus->slv_wr_ind - left_in_fifo;
+	bus->slv_wr_size = bus->slv_wr_size + left_in_fifo;
+
+	if (bus->slv_wr_ind < 0)
+		bus->slv_wr_ind += SMBUS_FIFO_SIZE;
+
+	return left_in_fifo;
+}
+
+static void npcm_i2c_slave_rd_wr(struct npcm_i2c *bus)
+{
+	if (FIELD_GET(NPCM_SMBST_XMIT, ioread8(bus->reg + NPCM_SMBST))) {
+		// Slave got an address match with direction bit 1 so
+		// it should transmit data
+		// Write till the master will NACK
+		bus->operation = SMB_WRITE_OPER;
+		npcm_smb_slave_xmit(bus,
+				    bus->adap.quirks->max_write_len,
+				    bus->slv_wr_buf);
+	} else {
+		// Slave got an address match with direction bit 0
+		// so it should receive data.
+		// this module does not support saying no to bytes.
+		// it will always ACK.
+		bus->operation = SMB_READ_OPER;
+		npcm_smb_read_from_fifo(bus, npcm_smb_get_fifo_fullness(bus));
+		bus->stop_ind = SMB_SLAVE_RCV_IND;
+		npcm_i2c_slave_send_rd_buf(bus);
+		npcm_smb_slave_receive(bus,
+				       bus->adap.quirks->max_read_len,
+				       bus->slv_rd_buf);
+	}
+}
+
+static irqreturn_t npcm_smb_int_slave_handler(struct npcm_i2c *bus)
+{
+	irqreturn_t ret = IRQ_NONE;
+	u8 smbst = ioread8(bus->reg + NPCM_SMBST);
+	// Slave: A NACK has occurred
+	if (FIELD_GET(NPCM_SMBST_NEGACK, smbst)) {
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_NACK);
+		bus->stop_ind = SMB_NACK_IND;
+		npcm_i2c_slave_wr_buf_sync(bus);
+		if (bus->fifo_use)
+			// clear the FIFO
+			iowrite8(NPCM_SMBFIF_CTS_CLR_FIFO,
+				 bus->reg + NPCM_SMBFIF_CTS);
+
+		// In slave write, NACK is OK, otherwise it is a problem
+		bus->stop_ind = SMB_NO_STATUS_IND;
+		bus->operation = SMB_NO_OPER;
+		bus->own_slave_addr = 0xFF;
+
+		// Slave has to wait for SMB_STOP to decide this is the end
+		// of the transaction.
+		// Therefore transaction is not yet considered as done
+		iowrite8(NPCM_SMBST_NEGACK, bus->reg + NPCM_SMBST);
+
+		ret = IRQ_HANDLED;
+	}
+
+	// Slave mode: a Bus Error (BER) has been identified
+	if (FIELD_GET(NPCM_SMBST_BER, smbst)) {
+		// Check whether bus arbitration or Start or Stop during data
+		// xfer bus arbitration problem should not result in recovery
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_BER_SLV);
+		bus->stop_ind = SMB_BUS_ERR_IND;
+
+		// wait for bus busy before clear fifo
+		iowrite8(NPCM_SMBFIF_CTS_CLR_FIFO, bus->reg + NPCM_SMBFIF_CTS);
+
+		bus->state = SMB_IDLE;
+
+		// in BER case we might get 2 interrupts: one for slave one for
+		// master ( for a channel which is master\slave switching)
+		if (completion_done(&bus->cmd_complete) == false) {
+			bus->cmd_err = -EIO;
+			complete(&bus->cmd_complete);
+		}
+		bus->own_slave_addr = 0xFF;
+		iowrite8(NPCM_SMBST_BER, bus->reg + NPCM_SMBST);
+		ret =  IRQ_HANDLED;
+	}
+
+	// A Slave Stop Condition has been identified
+	if (FIELD_GET(NPCM_SMBST_SLVSTP, smbst)) {
+		int bytes_in_fifo = npcm_smb_get_fifo_fullness(bus);
+
+		bus->stop_ind = SMB_SLAVE_DONE_IND;
+
+		if (bus->operation == SMB_READ_OPER) {
+			npcm_smb_read_from_fifo(bus, bytes_in_fifo);
+
+			// Slave done transmitting or receiving
+			// if the buffer is empty nothing will be sent
+		}
+
+		// Slave done transmitting or receiving
+		// if the buffer is empty nothing will be sent
+		npcm_i2c_slave_send_rd_buf(bus);
+
+		bus->stop_ind = SMB_NO_STATUS_IND;
+
+		// Note, just because we got here, it doesn't mean we through
+		// away the wr buffer.
+		// we keep it until the next received offset.
+		bus->operation = SMB_NO_OPER;
+		bus->int_cnt = 0;
+		bus->event_log_prev = bus->event_log;
+		bus->event_log = 0;
+		bus->own_slave_addr = 0xFF;
+
+		i2c_slave_event(bus->slave, I2C_SLAVE_STOP, 0);
+
+		iowrite8(NPCM_SMBST_SLVSTP, bus->reg + NPCM_SMBST);
+
+		if (bus->fifo_use) {
+			npcm_smb_clear_fifo_int(bus);
+			npcm_smb_clear_rx_fifo(bus);
+			npcm_smb_clear_tx_fifo(bus);
+
+			iowrite8(NPCM_SMBFIF_CTS_CLR_FIFO,
+				 bus->reg + NPCM_SMBFIF_CTS);
+		}
+
+		bus->state = SMB_IDLE;
+		ret =  IRQ_HANDLED;
+	}
+
+	// restart condition occurred and Rx-FIFO was not empty
+	if (bus->fifo_use && FIELD_GET(NPCM_SMBFIF_CTS_SLVRSTR,
+				       ioread8(bus->reg + NPCM_SMBFIF_CTS))) {
+		bus->stop_ind = SMB_SLAVE_RESTART_IND;
+
+		bus->master_or_slave = SMB_SLAVE;
+
+		if (bus->operation == SMB_READ_OPER)
+			npcm_smb_read_from_fifo(bus,
+						npcm_smb_get_fifo_fullness(bus)
+						);
+
+		bus->operation = SMB_WRITE_OPER;
+
+		iowrite8(0, bus->reg + NPCM_SMBRXF_CTL);
+
+		iowrite8(NPCM_SMBFIF_CTS_CLR_FIFO | NPCM_SMBFIF_CTS_SLVRSTR |
+			 NPCM_SMBFIF_CTS_RXF_TXE, bus->reg + NPCM_SMBFIF_CTS);
+
+		npcm_i2c_slave_rd_wr(bus);
+
+		ret =  IRQ_HANDLED;
+	}
+
+	// A Slave Address Match has been identified
+	if (FIELD_GET(NPCM_SMBST_NMATCH, smbst)) {
+		u8 info = 0;
+
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_NMATCH_SLV);
+		// Address match automatically implies slave mode
+		bus->master_or_slave = SMB_SLAVE;
+
+		npcm_smb_clear_fifo_int(bus);
+		npcm_smb_clear_rx_fifo(bus);
+		npcm_smb_clear_tx_fifo(bus);
+		iowrite8(0, bus->reg + NPCM_SMBTXF_CTL);
+		iowrite8(SMBUS_FIFO_SIZE, bus->reg + NPCM_SMBRXF_CTL);
+
+		if (FIELD_GET(NPCM_SMBST_XMIT, smbst)) {
+			bus->operation = SMB_WRITE_OPER;
+		} else {
+			i2c_slave_event(bus->slave, I2C_SLAVE_WRITE_REQUESTED,
+					&info);
+			bus->operation = SMB_READ_OPER;
+		}
+
+		if (bus->own_slave_addr == 0xFF) { // unknown address
+			// Check which type of address match
+			if (FIELD_GET(NPCM_SMBCST_MATCH,
+				      ioread8(bus->reg + NPCM_SMBCST))) {
+				u16 addr;
+				enum smb_addr eaddr;
+
+				addr = ((ioread8(bus->reg + NPCM_SMBCST3) &
+					 0x7) << 7) |
+					(ioread8(bus->reg + NPCM_SMBCST2) &
+					 0x7F);
+
+				info = ffs(addr);
+				eaddr = (enum smb_addr)info;
+
+				addr = FIELD_GET(NPCM_SMBADDR_A,
+						 npcm_smb_get_slave_addr(bus,
+									 eaddr)
+						);
+				bus->own_slave_addr = addr;
+
+				if (bus->PEC_mask & BIT(info))
+					bus->PEC_use = true;
+				else
+					bus->PEC_use = false;
+			} else {
+				if (FIELD_GET(NPCM_SMBCST_GCMATCH,
+					      ioread8(bus->reg + NPCM_SMBCST)))
+					bus->own_slave_addr = 0;
+				if (FIELD_GET(NPCM_SMBCST_ARPMATCH,
+					      ioread8(bus->reg + NPCM_SMBCST)))
+					bus->own_slave_addr = 0x61;
+			}
+		} else {
+			//  Slave match can happen in two options:
+			//  1. Start, SA, read	(slave read without further ado)
+			//  2. Start, SA, read, data, restart, SA, read,  ...
+			//     (slave read in fragmented mode)
+			//  3. Start, SA, write, data, restart, SA, read, ..
+			//     (regular write-read mode)
+			if ((bus->state == SMB_OPER_STARTED &&
+			     bus->operation == SMB_READ_OPER &&
+			     bus->stop_ind == SMB_SLAVE_XMIT_IND) ||
+			     bus->stop_ind == SMB_SLAVE_RCV_IND) {
+				// slave transmit after slave receive w/o Slave
+				// Stop implies repeated start
+				bus->stop_ind = SMB_SLAVE_RESTART_IND;
+			}
+		}
+
+		if (FIELD_GET(NPCM_SMBST_XMIT, smbst))
+			bus->stop_ind = SMB_SLAVE_XMIT_IND;
+		else
+			bus->stop_ind = SMB_SLAVE_RCV_IND;
+
+		bus->state = SMB_SLAVE_MATCH;
+
+		npcm_i2c_slave_rd_wr(bus);
+
+		iowrite8(NPCM_SMBST_NMATCH, bus->reg + NPCM_SMBST);
+		ret =  IRQ_HANDLED;
+	}
+
+	// Slave SDA status is set - transmit or receive, slave
+	if (FIELD_GET(NPCM_SMBST_SDAST, smbst) ||
+	    (bus->fifo_use   &&
+	    (npcm_smb_tx_fifo_empty(bus) || npcm_smb_rx_fifo_full(bus)))) {
+		npcm_i2c_slave_rd_wr(bus);
+
+		iowrite8(NPCM_SMBST_SDAST, bus->reg + NPCM_SMBST);
+
+		ret =  IRQ_HANDLED;
+	} //SDAST
+
+	return ret;
+}
+
+static int  npcm_i2c_reg_slave(struct i2c_client *client)
+{
+	unsigned long lock_flags;
+	struct npcm_i2c *bus = i2c_get_adapdata(client->adapter);
+
+	bus->slave = client;
+
+	if (!bus->slave)
+		return -EINVAL;
+
+	if (client->flags & I2C_CLIENT_TEN)
+		return -EAFNOSUPPORT;
+
+	spin_lock_irqsave(&bus->lock, lock_flags);
+
+	npcm_smb_init_params(bus);
+	bus->slv_rd_size = 0;
+	bus->slv_wr_size = 0;
+	bus->slv_rd_ind = 0;
+	bus->slv_wr_ind = 0;
+	if (client->flags & I2C_CLIENT_PEC)
+		bus->PEC_use = true;
+
+	dev_info(bus->dev, "I2C%d register slave SA=0x%x, PEC=%d\n", bus->num,
+		 client->addr, bus->PEC_use);
+
+	npcm_smb_slave_enable_l(bus, SMB_SLAVE_ADDR1, client->addr, true);
+
+	npcm_smb_clear_fifo_int(bus);
+	npcm_smb_clear_rx_fifo(bus);
+	npcm_smb_clear_tx_fifo(bus);
+
+	spin_unlock_irqrestore(&bus->lock, lock_flags);
+
+	return 0;
+}
+
+static int  npcm_i2c_unreg_slave(struct i2c_client *client)
+{
+	struct npcm_i2c *bus = client->adapter->algo_data;
+	unsigned long lock_flags;
+
+	spin_lock_irqsave(&bus->lock, lock_flags);
+	if (!bus->slave) {
+		spin_unlock_irqrestore(&bus->lock, lock_flags);
+		return -EINVAL;
+	}
+
+	npcm_smb_remove_slave_addr(bus, client->addr);
+
+	bus->slave = NULL;
+	spin_unlock_irqrestore(&bus->lock, lock_flags);
+
+	return 0;
+}
+#endif // CONFIG_I2C_SLAVE
+
+static void npcm_smb_master_fifo_read(struct npcm_i2c *bus)
+{
+	int rcount;
+	int fifo_bytes;
+	enum smb_state_ind ind = SMB_MASTER_DONE_IND;
+
+	fifo_bytes = npcm_smb_get_fifo_fullness(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 * SMBUS_FIFO_SIZE) && rcount > SMBUS_FIFO_SIZE)
+		fifo_bytes = (u8)(rcount - SMBUS_FIFO_SIZE);
+
+	if ((rcount - fifo_bytes) <= 0) {
+		// last bytes are about to be read - end of transaction.
+		// Stop should be set before reading last byte.
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_READ4);
+
+		bus->state = SMB_STOP_PENDING;
+		bus->stop_ind = ind;
+
+		npcm_smb_eob_int(bus, true);
+		npcm_smb_master_stop(bus);
+		npcm_smb_read_from_fifo(bus, fifo_bytes);
+	} else {
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_READ3);
+		npcm_smb_read_from_fifo(bus, fifo_bytes);
+		rcount = bus->rd_size - bus->rd_ind;
+		npcm_smb_set_fifo(bus, rcount, -1);
+	}
+}
+
+static void npcm_smb_int_master_handler_write(struct npcm_i2c *bus)
+{
+	u16 wcount;
+
+	NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_WRITE);
+	if (bus->fifo_use)
+		npcm_smb_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_smb_get_fifo_fullness(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 a pure wr operation
+			npcm_smb_eob_int(bus, true);
+
+			bus->state = SMB_STOP_PENDING;
+			bus->stop_ind = SMB_MASTER_DONE_IND;
+
+			npcm_smb_master_stop(bus);
+			// Clear SDA Status bit (by writing dummy byte)
+			npcm_smb_wr_byte(bus, 0xFF);
+
+		} else {
+			// last write-byte written on previous int - need to
+			// restart & send slave address
+			npcm_smb_set_fifo(bus, bus->rd_size, -1);
+
+			// Generate repeated start upon next write to SDA
+			npcm_smb_master_start(bus);
+
+			if (bus->rd_size == 1)
+				// 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
+				npcm_smb_stall_after_start(bus, true);
+
+			// Next int will occur on read
+			bus->operation = SMB_READ_OPER;
+
+			// send the slave address in read direction
+			npcm_smb_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_smb_wr_byte(bus, bus->wr_buf[bus->wr_ind++]);
+		} else {
+			wcount = bus->wr_size - bus->wr_ind;
+			npcm_smb_set_fifo(bus, -1, wcount);
+			npcm_smb_write_to_fifo_master(bus, wcount);
+		}
+	}
+}
+
+static void npcm_smb_int_master_handler_read(struct npcm_i2c *bus)
+{
+	u16 block_extra_bytes_size;
+	u8 data;
+
+	// Master read operation (pure read or following a write operation).
+	NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_READ);
+
+	// added bytes to the packet:
+	block_extra_bytes_size = (u8)bus->read_block_use + (u8)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:
+		// in block protocol first byte is the size
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_READ1);
+		if (bus->read_block_use) {
+			// first byte in block protocol is the size:
+			npcm_smb_rd_byte(bus, &data);
+
+			// if slave returned illegal size. read up to 32 bytes.
+			if (data >= I2C_SMBUS_BLOCK_MAX)
+				data = I2C_SMBUS_BLOCK_MAX;
+
+			// is data is 0 -> not supported. read at least one byte
+			if (data == 0)
+				data = 1;
+
+			bus->rd_size = data + block_extra_bytes_size;
+
+			bus->rd_buf[bus->rd_ind++] = data;
+
+			// clear RX FIFO interrupt status:
+			if (bus->fifo_use) {
+				iowrite8(NPCM_SMBFIF_CTS_RXF_TXE |
+					 ioread8(bus->reg + NPCM_SMBFIF_CTS),
+					 bus->reg + NPCM_SMBFIF_CTS);
+			}
+
+			npcm_smb_set_fifo(bus, (bus->rd_size - 1), -1);
+			npcm_smb_stall_after_start(bus, false);
+		} else {
+			npcm_smb_clear_tx_fifo(bus);
+			npcm_smb_master_fifo_read(bus);
+		}
+	} else {
+		if (bus->rd_size == block_extra_bytes_size &&
+		    bus->read_block_use) {
+			bus->state = SMB_STOP_PENDING;
+			bus->stop_ind = SMB_BLOCK_BYTES_ERR_IND;
+			bus->cmd_err = -EIO;
+			npcm_smb_eob_int(bus, true);
+			npcm_smb_master_stop(bus);
+			npcm_smb_read_from_fifo(bus,
+						npcm_smb_get_fifo_fullness(bus)
+						);
+		} else {
+			NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_READ2);
+			npcm_smb_master_fifo_read(bus);
+		}
+	}
+}
+
+static irqreturn_t npcm_smb_int_master_handler(struct npcm_i2c *bus)
+{
+	irqreturn_t ret = IRQ_NONE;
+	u8 fif_cts;
+
+	if (FIELD_GET(NPCM_SMBST_NMATCH, ioread8(bus->reg + NPCM_SMBST))) {
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_NMATCH_MSTR);
+		iowrite8(NPCM_SMBST_NMATCH, bus->reg + NPCM_SMBST);
+		npcm_smb_nack(bus);
+		bus->stop_ind = SMB_BUS_ERR_IND;
+		npcm_smb_callback(bus, bus->stop_ind, npcm_smb_get_index(bus));
+
+		return IRQ_HANDLED;
+	}
+	// A NACK has occurred
+	if (FIELD_GET(NPCM_SMBST_NEGACK, ioread8(bus->reg + NPCM_SMBST))) {
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_NACK);
+		if (bus->fifo_use) {
+			// if there are still untransmitted bytes in TX FIFO
+			// reduce them from wr_ind
+			if (bus->operation == SMB_WRITE_OPER)
+				bus->wr_ind -= npcm_smb_get_fifo_fullness(bus);
+
+			// clear the FIFO
+			iowrite8(NPCM_SMBFIF_CTS_CLR_FIFO,
+				 bus->reg + NPCM_SMBFIF_CTS);
+		}
+
+		// In master write operation, NACK is a problem
+		// number of bytes sent to master less than required
+		bus->stop_ind = SMB_NACK_IND;
+		// Only current master is allowed to issue Stop Condition
+		if (npcm_smb_is_master(bus)) {
+			// stopping in the middle, not waiting for ints anymore
+			npcm_smb_eob_int(bus,  false);
+
+			npcm_smb_master_stop(bus);
+
+			// Clear NEGACK, STASTR and BER bits
+			// In Master mode, NEGACK should be cleared only after
+			// generating STOP.
+			// In such case, the bus is released from stall only
+			// after the software clears NEGACK bit.
+			// Then a Stop condition is sent.
+			iowrite8(NPCM_SMBST_BER | NPCM_SMBST_NEGACK |
+				 NPCM_SMBST_STASTR, bus->reg + NPCM_SMBST);
+
+			npcm_smb_wait_for_bus_free(bus, false);
+		}
+		bus->state = SMB_IDLE;
+
+		// In Master mode, NACK should be cleared only after
+		// generating STOP.
+		// In such case, the bus is released from stall only after the
+		// software clears NACK bit.
+		// Then a Stop condition is sent.
+		npcm_smb_callback(bus, bus->stop_ind, bus->wr_ind);
+		return IRQ_HANDLED;
+	}
+
+	// Master mode: a Bus Error has been identified
+	if (FIELD_GET(NPCM_SMBST_BER, ioread8(bus->reg + NPCM_SMBST))) {
+		// Check whether bus arbitration or Start or Stop during data
+		// xfer bus arbitration problem should not result in recovery
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_BER);
+		bus->stop_ind = SMB_BUS_ERR_IND;
+		if (npcm_smb_is_master(bus)) {
+			npcm_smb_master_abort(bus);
+		} else {
+			// Clear NEGACK, STASTR and BER bits
+			iowrite8(NPCM_SMBST_BER | NPCM_SMBST_NEGACK |
+				 NPCM_SMBST_STASTR, bus->reg + NPCM_SMBST);
+
+			// Clear BB (BUS BUSY) bit
+			iowrite8(NPCM_SMBCST_BB, bus->reg + NPCM_SMBCST);
+
+			bus->cmd_err = -EAGAIN;
+			npcm_smb_callback(bus, bus->stop_ind,
+					  npcm_smb_get_index(bus));
+		}
+		bus->state = SMB_IDLE;
+		ret =  IRQ_HANDLED;
+		return ret;
+	}
+
+	// A Master End of Busy (meaning Stop Condition happened)
+	// End of Busy int is on and End of Busy is set
+	if ((FIELD_GET(NPCM_SMBCTL1_EOBINTE,
+		       ioread8(bus->reg + NPCM_SMBCTL1)) == 1) &&
+	    (FIELD_GET(NPCM_SMBCST3_EO_BUSY,
+		       ioread8(bus->reg + NPCM_SMBCST3)))) {
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_EOB);
+		npcm_smb_eob_int(bus, false);
+		bus->state = SMB_IDLE;
+		npcm_smb_callback(bus, bus->stop_ind, bus->rd_ind);
+		return IRQ_HANDLED;
+	}
+
+	// Address sent and requested stall occurred (Master mode)
+	if (FIELD_GET(NPCM_SMBST_STASTR, ioread8(bus->reg + NPCM_SMBST))) {
+		NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_STALL);
+
+		if (npcm_smb_is_quick(bus)) {
+			bus->state = SMB_STOP_PENDING;
+			bus->stop_ind = SMB_MASTER_DONE_IND;
+			npcm_smb_eob_int(bus, true);
+			npcm_smb_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_smb_nack(bus);
+		}
+
+		// Reset stall-after-address-byte
+		npcm_smb_stall_after_start(bus, false);
+
+		// Clear stall only after setting STOP
+		iowrite8(NPCM_SMBST_STASTR, bus->reg + NPCM_SMBST);
+
+		ret =  IRQ_HANDLED;
+	}
+
+	// SDA status is set - TX or RX, master
+	if (FIELD_GET(NPCM_SMBST_SDAST, ioread8(bus->reg + NPCM_SMBST)) ||
+	    (bus->fifo_use &&
+	    (npcm_smb_tx_fifo_empty(bus) || npcm_smb_rx_fifo_full(bus)))) {
+		// Status Bit is cleared by writing to or reading from SDA
+		// (depending on current direction)
+
+		// Send address:
+		if (bus->state == SMB_IDLE) {
+			if (npcm_smb_is_master(bus)) {
+				bus->stop_ind = SMB_WAKE_UP_IND;
+
+				// test stall on start
+				if (npcm_smb_is_quick(bus) ||
+				    bus->read_block_use)
+					// Need to stall after successful
+					// completion of sending address byte
+					npcm_smb_stall_after_start(bus, true);
+				else
+					npcm_smb_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_smb_stall_after_start(bus, true);
+
+				// Initiate SMBus master transaction
+				// Generate a Start condition on the SMBus
+
+				// select bank 1 for FIFO regs
+				npcm_smb_select_bank(bus, SMB_BANK_1);
+
+				fif_cts = ioread8(bus->reg + NPCM_SMBFIF_CTS);
+
+				// clear FIFO and relevant status bits.
+				iowrite8((fif_cts & ~NPCM_SMBFIF_CTS_SLVRSTR)
+					| NPCM_SMBFIF_CTS_CLR_FIFO,
+					 bus->reg + NPCM_SMBFIF_CTS);
+
+				// and enable it
+				iowrite8((fif_cts & ~NPCM_SMBFIF_CTS_SLVRSTR)
+					| NPCM_SMBFIF_CTS_RXF_TXE,
+					 bus->reg + NPCM_SMBFIF_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
+				// 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_smb_set_fifo(bus, -1,
+							  bus->wr_size);
+				else
+					npcm_smb_set_fifo(bus, bus->rd_size,
+							  -1);
+
+				bus->state = SMB_OPER_STARTED;
+
+				if (npcm_smb_is_quick(bus) || bus->wr_size)
+					npcm_smb_wr_byte(bus, bus->dest_addr);
+				else
+					npcm_smb_wr_byte(bus, bus->dest_addr |
+							      0x01);
+			}
+
+			return IRQ_HANDLED;
+		// SDA status is set - transmit or receive: Handle master mode
+		} else {
+			if ((NPCM_SMBST_XMIT &
+			     ioread8(bus->reg + NPCM_SMBST)) == 0) {
+				bus->operation = SMB_READ_OPER;
+				npcm_smb_int_master_handler_read(bus);
+			} else {
+				bus->operation = SMB_WRITE_OPER;
+				npcm_smb_int_master_handler_write(bus);
+			}
+		}
+		ret =  IRQ_HANDLED;
+	}
+
+	return ret;
+}
+
+static int npcm_smb_get_SCL(struct i2c_adapter *_adap)
+{
+	unsigned int ret = 0;
+	struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);
+	u32 offset = 0;
+
+	offset = 0;
+	ret = FIELD_GET(SMBCTL3_SCL_LVL, ioread32(bus->reg + NPCM_SMBCTL3));
+
+	pr_debug("i2c%d get SCL 0x%08X\n", bus->num, ret);
+
+	return (ret >> (offset)) & 0x01;
+}
+
+static int npcm_smb_get_SDA(struct i2c_adapter *_adap)
+{
+	unsigned int ret = 0;
+	struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);
+	u32 offset = 0;
+
+	offset = 0;
+	ret = FIELD_GET(SMBCTL3_SDA_LVL, ioread32(bus->reg + NPCM_SMBCTL3));
+
+	pr_debug("i2c%d get SDA 0x%08X\n", bus->num, ret);
+
+	return (ret >> (offset)) & 0x01;
+}
+
+// recovery using TGCLK functionality of the module
+static int npcm_smb_recovery_tgclk(struct i2c_adapter *_adap)
+{
+	int  iter = 27;	  // Allow 3 bytes to be sent by the Slave
+	int  retries = 0;
+	bool done = false;
+	int  status = -(ENOTRECOVERABLE);
+	u8   fif_cts;
+	struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);
+
+	dev_dbg(bus->dev, "TGCLK recovery bus%d\n", bus->num);
+
+	if ((npcm_smb_get_SDA(_adap) == 1) && (npcm_smb_get_SCL(_adap) == 1)) {
+		dev_dbg(bus->dev, "TGCLK recovery bus%d: skipped bus not stuck",
+			bus->num);
+		npcm_smb_reset(bus);
+		return status;
+	}
+
+	// Disable int
+	npcm_smb_int_enable(bus, false);
+
+	npcm_smb_disable(bus);
+	npcm_smb_enable(bus);
+	iowrite8(NPCM_SMBCST_BB, bus->reg + NPCM_SMBCST);
+	npcm_smb_clear_tx_fifo(bus);
+	npcm_smb_clear_rx_fifo(bus);
+	iowrite8(0, bus->reg + NPCM_SMBRXF_CTL);
+	iowrite8(0, bus->reg + NPCM_SMBTXF_CTL);
+	npcm_smb_stall_after_start(bus, false);
+
+	// select bank 1 for FIFO regs
+	npcm_smb_select_bank(bus, SMB_BANK_1);
+
+	fif_cts = ioread8(bus->reg + NPCM_SMBFIF_CTS);
+
+	// clear FIFO and relevant status bits.
+	iowrite8((fif_cts & ~NPCM_SMBFIF_CTS_SLVRSTR) |
+		  NPCM_SMBFIF_CTS_CLR_FIFO,
+		  bus->reg + NPCM_SMBFIF_CTS);
+
+	npcm_smb_set_fifo(bus, -1, 0);
+
+	// Check If the SDA line is active (low)
+	if (npcm_smb_get_SDA(_adap) == 0) {
+		// Repeat the following sequence until SDA is released
+		do {
+			// Issue a single SCL cycle
+			iowrite8(NPCM_SMBCST_TGSCL, bus->reg + NPCM_SMBCST);
+			retries = 10;
+			while (retries != 0 &&
+			       FIELD_GET(NPCM_SMBCST_TGSCL,
+					 ioread8(bus->reg + NPCM_SMBCST))) {
+				udelay(20);
+				retries--;
+			}
+
+			// tgclk failed to toggle
+			if (retries == 0)
+				dev_dbg(bus->dev, "\t toggle timeout\n");
+			// If SDA line is inactive (high), stop
+			if (npcm_smb_get_SDA(_adap))
+				done = true;
+		} while ((!done) && (--iter != 0));
+
+		// If SDA line is released: send start-addr-stop, to re-sync.
+		if (done) {
+			npcm_smb_master_start(bus);
+
+			// Wait until START condition is sent, or RETRIES_NUM
+			retries = RETRIES_NUM;
+			while (retries && !npcm_smb_is_master(bus)) {
+				udelay(20);
+				retries--;
+			}
+
+			// If START condition was sent
+			if (retries > 0) {
+				// Send an address byte in write direction:
+				npcm_smb_wr_byte(bus, bus->dest_addr);
+				udelay(200);
+				npcm_smb_master_stop(bus);
+				udelay(200);
+				status = 0;
+			}
+		}
+	}
+
+	// if bus is still stuck: total reset: set SCL low for 35ms:
+	if (unlikely(npcm_smb_get_SDA(_adap) == 0)) {
+		// Generate a START, to synchronize Master and Slave
+		npcm_smb_master_start(bus);
+
+		// Wait until START condition is sent, or RETRIES_NUM
+		retries = RETRIES_NUM;
+		while (retries && !npcm_smb_is_master(bus))
+			retries--;
+
+		// set SCL low for a long time (note: this is unlikely)
+		usleep_range(25000, 35000);
+		npcm_smb_master_stop(bus);
+		udelay(200);
+		status = 0;
+	}
+
+	dev_dbg(bus->dev, "TGCLK done, iter = %d, done = %d, retries = %d\n",
+		27 - iter, done, retries);
+	// Enable SMB int and New Address Match int source
+	iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) | NPCM_SMBCTL1_NMINTE) &
+		 ~NPCM_SMBCTL1_RWS_FIELDS,
+		 bus->reg + NPCM_SMBCTL1);
+	npcm_smb_reset(bus);
+	npcm_smb_int_enable(bus, true);
+	return status;
+}
+
+// recovery using bit banging functionality of the module
+static int npcm_smb_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_smb_recovery_tgclk;
+	rinfo->prepare_recovery = NULL;
+	rinfo->unprepare_recovery = NULL;
+	rinfo->set_scl = NULL;
+	rinfo->set_sda = NULL;
+
+	dev_dbg(bus->dev, "i2c gpio recovery using TGCLK\n");
+
+	rinfo->get_scl = npcm_smb_get_SCL;
+	rinfo->get_sda = npcm_smb_get_SDA;
+
+	_adap->bus_recovery_info = rinfo;
+
+	return 0;
+}
+
+static bool npcm_smb_init_clk(struct npcm_i2c *bus, u32 bus_freq)
+{
+	u32  k1 = 0;
+	u32  k2 = 0;
+	u8   dbnct = 0;
+	u32  sclfrq = 0;
+	u8   hldt = 7;
+	bool fast_mode = false;
+	u32  src_clk_freq; // in KHz
+
+	src_clk_freq = bus->apb_clk / 1000;
+	bus->bus_freq = bus_freq;
+
+	if (bus_freq <= SMBUS_FREQ_100KHZ) {
+		sclfrq = src_clk_freq / (bus_freq * 4);
+
+		if (sclfrq < SCLFRQ_MIN || sclfrq > SCLFRQ_MAX)
+			return false;
+
+		if (src_clk_freq >= 40000)
+			hldt = 17;
+		else if (src_clk_freq >= 12500)
+			hldt = 15;
+		else
+			hldt = 7;
+	}
+
+	else if (bus_freq == SMBUS_FREQ_400KHZ) {
+		sclfrq = 0;
+		fast_mode = true;
+
+		if (src_clk_freq < 7500)
+			// 400KHZ cannot be supported for core clock < 7.5 MHZ
+			return false;
+
+		else if (src_clk_freq >= 50000) {
+			k1 = 80;
+			k2 = 48;
+			hldt = 12;
+			dbnct = 7;
+		}
+
+		// Master or Slave with frequency > 25 MHZ
+		else if (src_clk_freq > 25000) {
+			hldt = (u8)__KERNEL_DIV_ROUND_UP(src_clk_freq * 300,
+							 1000000) + 7;
+
+			k1 = __KERNEL_DIV_ROUND_UP(src_clk_freq * 1600,
+						   1000000);
+			k2 = __KERNEL_DIV_ROUND_UP(src_clk_freq * 900,
+						   1000000);
+			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 false;
+		}
+	}
+
+	else if (bus_freq == SMBUS_FREQ_1MHZ) {
+		sclfrq = 0;
+		fast_mode = true;
+
+		if (src_clk_freq < 24000)
+		// 1MHZ cannot be supported for master core clock < 15 MHZ
+		// or slave core clock < 24 MHZ
+			return false;
+
+		k1 = round_up((__KERNEL_DIV_ROUND_UP(src_clk_freq * 620,
+						     1000000)), 2);
+		k2 = round_up((__KERNEL_DIV_ROUND_UP(src_clk_freq * 380,
+						     1000000) + 1), 2);
+		if (k1 < SCLFRQ_MIN || k1 > SCLFRQ_MAX ||
+		    k2 < SCLFRQ_MIN || k2 > SCLFRQ_MAX)
+			return false;
+
+		// Master or Slave with frequency > 40 MHZ
+		if (src_clk_freq > 40000) {
+			// Set HLDT:
+			// SDA hold time:  (HLDT-7) * T(CLK) >= 120
+			// HLDT = 120/T(CLK) + 7 = 120 * FREQ(CLK) + 7
+			hldt = (u8)__KERNEL_DIV_ROUND_UP(src_clk_freq * 120,
+							 1000000) + 7;
+		} else {
+			hldt = 7;
+			dbnct = 2;
+		}
+	}
+
+	// Frequency larger than 1 MHZ
+	else
+		return false;
+
+	// After clock parameters calculation update reg (ENABLE should be 0):
+	iowrite8(FIELD_PREP(SMBCTL2_SCLFRQ6_0, sclfrq & 0x7F),
+		 bus->reg + NPCM_SMBCTL2);
+
+	// force to bank 0, set SCL and fast mode
+	iowrite8(FIELD_PREP(SMBCTL3_400K_MODE, fast_mode) |
+		 FIELD_PREP(SMBCTL3_SCLFRQ8_7, (sclfrq >> 7) & 0x3),
+		 bus->reg + NPCM_SMBCTL3);
+
+	// Select Bank 0 to access NPCM_SMBCTL4/NPCM_SMBCTL5
+	npcm_smb_select_bank(bus, SMB_BANK_0);
+
+	if (bus_freq >= SMBUS_FREQ_400KHZ) {
+		// Set SCL Low/High Time:
+		// k1 = 2 * SCLLT7-0 -> Low Time  = k1 / 2
+		// k2 = 2 * SCLLT7-0 -> High Time = k2 / 2
+		iowrite8((u8)k1 / 2, bus->reg + NPCM_SMBSCLLT);
+		iowrite8((u8)k2 / 2, bus->reg + NPCM_SMBSCLHT);
+
+		iowrite8(dbnct, bus->reg + NPCM_SMBCTL5);
+	}
+
+	iowrite8(hldt, bus->reg + NPCM_SMBCTL4);
+
+	// Return to Bank 1, and stay there by default:
+	npcm_smb_select_bank(bus, SMB_BANK_1);
+
+	return true;
+}
+
+static bool npcm_smb_init_module(struct npcm_i2c *bus, enum smb_mode mode,
+				 u32 bus_freq)
+{
+	// Check whether module already enabled or frequency is out of bounds
+	if ((bus->state != SMB_DISABLE && bus->state != SMB_IDLE) ||
+	    bus_freq < SMBUS_FREQ_MIN || bus_freq > SMBUS_FREQ_MAX)
+		return false;
+
+	npcm_smb_disable(bus);
+
+	// Configure FIFO mode :
+	if (FIELD_GET(SMB_VER_FIFO_EN, ioread8(bus->reg + SMB_VER))) {
+		bus->fifo_use = true;
+		npcm_smb_select_bank(bus, SMB_BANK_0);
+		iowrite8(ioread8(bus->reg + NPCM_SMBFIF_CTL) |
+			 NPCM_SMBFIF_CTL_FIFO_EN, bus->reg + NPCM_SMBFIF_CTL);
+		npcm_smb_select_bank(bus, SMB_BANK_1);
+	} else {
+		bus->fifo_use = false;
+	}
+
+	// Configure SMB module clock frequency
+	if (!npcm_smb_init_clk(bus, bus_freq)) {
+		dev_err(bus->dev, "npcm_smb_init_clk failed\n");
+		return false;
+	}
+
+	// Enable module (before configuring CTL1)
+	npcm_smb_enable(bus);
+	bus->state = SMB_IDLE;
+
+	// Enable SMB int and New Address Match int source
+	iowrite8((ioread8(bus->reg + NPCM_SMBCTL1) | NPCM_SMBCTL1_NMINTE) &
+		 ~NPCM_SMBCTL1_RWS_FIELDS,
+		 bus->reg + NPCM_SMBCTL1);
+
+	npcm_smb_int_enable(bus, true);
+
+	npcm_smb_reset(bus);
+
+	return true;
+}
+
+static int __npcm_i2c_init(struct npcm_i2c *bus, struct platform_device *pdev)
+{
+	u32 clk_freq;
+	int ret;
+
+	// Initialize the internal data structures
+	bus->state = SMB_DISABLE;
+	bus->master_or_slave = SMB_SLAVE;
+	bus->int_time_stamp = 0;
+	bus->slave = NULL;
+	bus->xmits = 0;
+
+	ret = of_property_read_u32(pdev->dev.of_node,
+				   "bus-frequency", &clk_freq);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Could not read bus-frequency property\n");
+		clk_freq = 100000;
+	}
+
+	ret = npcm_smb_init_module(bus, SMB_MASTER, clk_freq / 1000);
+	if (!ret) {
+		dev_err(&pdev->dev,
+			"npcm_smb_init_module() failed\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+static irqreturn_t npcm_i2c_bus_irq(int irq, void *dev_id)
+{
+	irqreturn_t ret;
+	struct npcm_i2c *bus = dev_id;
+
+	bus->int_cnt++;
+
+	if (npcm_smb_is_master(bus))
+		bus->master_or_slave = SMB_MASTER;
+
+	if (bus->master_or_slave == SMB_MASTER)	{
+		bus->int_time_stamp = jiffies;
+		ret = npcm_smb_int_master_handler(bus);
+		if (ret == IRQ_HANDLED)
+			return ret;
+	}
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+	if (bus->slave) {
+		bus->master_or_slave = SMB_SLAVE;
+		ret = npcm_smb_int_slave_handler(bus);
+		if (ret == IRQ_HANDLED)
+			return ret;
+	}
+#endif
+	return IRQ_HANDLED;
+}
+
+static bool npcm_smb_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 != SMB_IDLE) {
+		bus->cmd_err = -(EBUSY);
+		return false;
+	}
+
+	bus->xmits++;
+
+	bus->dest_addr = (u8)(slave_addr << 1);// Translate 7bit to 8bit format
+	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 write, 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 = SMB_READ_OPER;
+	else
+		bus->operation = SMB_WRITE_OPER;
+
+	bus->int_cnt = 0;
+	bus->event_log = 0;
+
+	if (bus->fifo_use) {
+		u8 smbfif_cts;
+		// select bank 1 for FIFO regs
+		npcm_smb_select_bank(bus, SMB_BANK_1);
+
+		smbfif_cts = ioread8(bus->reg + NPCM_SMBFIF_CTS);
+
+		// clear FIFO and relevant status bits.
+		iowrite8((smbfif_cts & (~NPCM_SMBFIF_CTS_SLVRSTR)) |
+			 NPCM_SMBFIF_CTS_CLR_FIFO,
+			 bus->reg + NPCM_SMBFIF_CTS);
+	}
+
+	bus->state = SMB_IDLE;
+
+	npcm_smb_stall_after_start(bus, true);
+	npcm_smb_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 (unlikely(bus->state == SMB_DISABLE)) {
+		dev_err(bus->dev, "I2C%d module is disabled", bus->num);
+		return -EINVAL;
+	}
+
+	if (num > 2 || num < 1) {
+		dev_err(bus->dev, "I2C cmd not supported num of msgs=%d", num);
+		return -EINVAL;
+	}
+
+	msg0 = &msgs[0];
+	slave_addr = msg0->addr;
+	if (msg0->flags & I2C_M_RD) { // read
+		if (num == 2) {
+			dev_err(bus->dev, "num=2 but 1st msg rd instead of wr");
+			return -EINVAL;
+		}
+		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 (slave_addr != msg1->addr) {
+				dev_err(bus->dev,
+					"SA==%02x but msg1->addr==%02x\n",
+				       slave_addr, msg1->addr);
+				return -EINVAL;
+			}
+			if ((msg1->flags & I2C_M_RD) == 0) {
+				dev_err(bus->dev,
+					"num = 2 but both msg are write.\n");
+				return -EINVAL;
+			}
+			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_SMBCST) & NPCM_SMBCST_BB;
+		if (!bus_busy && bus->slave)
+			iowrite8((bus->slave->addr & 0x7F),
+				 bus->reg + NPCM_SMBADDR1);
+		spin_unlock_irqrestore(&bus->lock, flags);
+
+		if (!bus_busy)
+			break;
+	} while (time_is_after_jiffies(time_left));
+
+	if (bus_busy) {
+		iowrite8(NPCM_SMBCST_BB, bus->reg + NPCM_SMBCST);
+		npcm_smb_reset(bus);
+		i2c_recover_bus(adap);
+		return -EAGAIN;
+	}
+
+	npcm_smb_init_params(bus);
+	bus->dest_addr = slave_addr;
+	bus->msgs = msgs;
+	bus->msgs_num = num;
+	bus->read_block_use = read_block;
+
+	reinit_completion(&bus->cmd_complete);
+
+	if (!npcm_smb_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) {
+			NPCM_I2C_EVENT_LOG(NPCM_I2C_EVENT_TO);
+			if (bus->master_or_slave == SMB_MASTER) {
+				dev_dbg(bus->dev,
+					"i2c%d TO = %d\n", bus->num, timeout);
+				i2c_recover_bus(adap);
+				bus->cmd_err = -EIO;
+				bus->state = SMB_IDLE;
+			}
+		}
+	}
+	ret = bus->cmd_err;
+
+	// if there was BER, check if need to recover the bus:
+	if (bus->cmd_err == -EAGAIN)
+		i2c_recover_bus(adap);
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+	// reenable slave if it was enabled
+	if (bus->slave)
+		iowrite8((bus->slave->addr & 0x7F) | NPCM_SMBADDR_SAEN,
+			 bus->reg + NPCM_SMBADDR1);
+#endif
+
+	// If nothing went wrong, return number of messages x-ferred.
+	if (ret >= 0)
+		return num;
+
+	// print errors apart from NACK
+	if (bus->cmd_err == -ENXIO)
+		dev_dbg(bus->dev, "cmd failed cmd_err = %d\n", ret);
+	return ret;
+}
+
+static u32 npcm_i2c_functionality(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_SMBUS_BLOCK_DATA |
+			I2C_FUNC_SLAVE | I2C_FUNC_SMBUS_PEC;
+}
+
+static const struct i2c_adapter_quirks npcm_i2c_quirks = {
+	.max_read_len = 32768,
+	.max_write_len = 32768,
+	.max_num_msgs = 2,
+	.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,
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+	.reg_slave	= npcm_i2c_reg_slave,
+	.unreg_slave	= npcm_i2c_unreg_slave,
+#endif
+};
+
+static int  npcm_i2c_probe_bus(struct platform_device *pdev)
+{
+	struct npcm_i2c *bus;
+	struct i2c_adapter *adap;
+	struct resource *res;
+	struct clk *i2c_clk;
+	int ret;
+	int num;
+
+	bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
+	if (!bus)
+		return -ENOMEM;
+
+#ifdef CONFIG_OF
+	num = of_alias_get_id(pdev->dev.of_node, "i2c");
+	bus->num = num;
+	i2c_clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(i2c_clk)) {
+		dev_err(bus->dev, " I2C probe failed: can't read clk\n");
+		return	-EPROBE_DEFER;
+	}
+	bus->apb_clk = clk_get_rate(i2c_clk);
+	dev_dbg(bus->dev, "I2C APB clock is %d\n", bus->apb_clk);
+#endif //  CONFIG_OF
+
+	gcr_regmap = syscon_regmap_lookup_by_compatible("nuvoton,npcm750-gcr");
+	if (IS_ERR(gcr_regmap)) {
+		dev_err(bus->dev, "%s: failed to find nuvoton,npcm750-gcr\n",
+			__func__);
+		return IS_ERR(gcr_regmap);
+	}
+	regmap_write(gcr_regmap, NPCM_I2CSEGCTL, I2CSEGCTL_VAL);
+	dev_dbg(bus->dev, "I2C%d: gcr mapped\n", bus->num);
+
+	clk_regmap = syscon_regmap_lookup_by_compatible("nuvoton,npcm750-clk");
+	if (IS_ERR(clk_regmap)) {
+		dev_err(bus->dev, "%s: failed to find nuvoton,npcm750-clk\n",
+			__func__);
+		return IS_ERR(clk_regmap);
+	}
+	dev_dbg(bus->dev, "I2C%d: clk mapped\n", bus->num);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	dev_dbg(bus->dev, "resource: %pR\n", res);
+	bus->reg = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR((bus)->reg))
+		return PTR_ERR((bus)->reg);
+	dev_dbg(bus->dev, "base = %p\n", bus->reg);
+
+	// Initialize the I2C adapter
+	spin_lock_init(&bus->lock);
+	init_completion(&bus->cmd_complete);
+
+	adap = &bus->adap;
+	adap->owner = THIS_MODULE;
+	adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD | I2C_CLIENT_SLAVE;
+	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;
+
+	bus->dev = &pdev->dev;
+	bus->slave = NULL;
+
+	bus->irq = platform_get_irq(pdev, 0);
+	if (bus->irq < 0) {
+		dev_err(bus->dev, "I2C platform_get_irq error\n");
+		return -ENODEV;
+	}
+	dev_dbg(bus->dev, "irq = %d\n", bus->irq);
+
+	ret = devm_request_irq(&pdev->dev, bus->irq, npcm_i2c_bus_irq, 0,
+			       dev_name(&pdev->dev), (void *)bus);
+
+	if (ret) {
+		dev_err(&pdev->dev, "I2C%d: request_irq fail\n", bus->num);
+		return ret;
+	}
+
+	ret = __npcm_i2c_init(bus, pdev);
+	if (ret < 0)
+		return ret;
+
+	ret = npcm_smb_recovery_init(adap);
+	if (ret)
+		return ret;
+
+	i2c_set_adapdata(adap, bus);
+
+	snprintf(bus->adap.name, sizeof(bus->adap.name), "Nuvoton i2c");
+
+	ret = i2c_add_numbered_adapter(&bus->adap);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "I2C%d: i2c_add_numbered_adapter fail\n",
+			bus->num);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, bus);
+
+	pr_info("npcm7xx I2C bus is %d registered\n", bus->adap.nr);
+
+	return 0;
+}
+
+static int  npcm_i2c_remove_bus(struct platform_device *pdev)
+{
+	unsigned long lock_flags;
+	struct npcm_i2c *bus = platform_get_drvdata(pdev);
+
+	spin_lock_irqsave(&bus->lock, lock_flags);
+	npcm_smb_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,
+	}
+};
+module_platform_driver(npcm_i2c_bus_driver);
+
+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");
+MODULE_VERSION(I2C_VERSION);