Re: [PATCH RESEND 1/1] i2c: Add support for Xilinx XPS IIC Bus Interface

["Richard Röjfors" <richard.rojfors-gfIc91nka+FZroRs9YW3xA@public.gmane.org>]

Hi Ben,

Thanks for the feedback! Comments below...

On 1/24/10 4:49 PM, Ben Dooks wrote:
> On Tue, Jan 19, 2010 at 05:01:16PM +0100, Richard R?jfors wrote:
>> This patch adds support for the Xilinx XPS IIC Bus Interface.
>>
>> The driver uses the dynamic mode, supporting to put several
>> I2C messages in the FIFO to reduce the number of interrupts.
>>
>> It has the same feature as ocores, it can be passed a list
>> of devices that will be added when the bus is probed.
>>
>> Signed-off-by: Richard R?jfors <richard.rojfors-gfIc91nka+FZroRs9YW3xA@public.gmane.org>
>> ---
>> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
>> index 5f318ce..44ff5c8 100644
>> --- a/drivers/i2c/busses/Kconfig
>> +++ b/drivers/i2c/busses/Kconfig
>> @@ -564,6 +564,16 @@ config I2C_VERSATILE
>>  	  This driver can also be built as a module.  If so, the module
>>  	  will be called i2c-versatile.
>>
>> +config I2C_XILINX
>> +	tristate "Xilinx I2C Controller"
>> +	depends on EXPERIMENTAL && HAS_IOMEM
>> +	help
>> +	  If you say yes to this option, support will be included for the
>> +	  Xilinx I2C controller.
>> +
>> +	  This driver can also be built as a module.  If so, the module
>> +	  will be called xilinx_i2c.
>> +
>>  comment "External I2C/SMBus adapter drivers"
>>
>>  config I2C_PARPORT
>> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
>> index 302c551..168f302 100644
>> --- a/drivers/i2c/busses/Makefile
>> +++ b/drivers/i2c/busses/Makefile
>> @@ -54,6 +54,7 @@ obj-$(CONFIG_I2C_SH_MOBILE)	+= i2c-sh_mobile.o
>>  obj-$(CONFIG_I2C_SIMTEC)	+= i2c-simtec.o
>>  obj-$(CONFIG_I2C_STU300)	+= i2c-stu300.o
>>  obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o
>> +obj-$(CONFIG_I2C_XILINX)	+= i2c-xiic.o
>>
>>  # External I2C/SMBus adapter drivers
>>  obj-$(CONFIG_I2C_PARPORT)	+= i2c-parport.o
>> diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
>> new file mode 100644
>> index 0000000..561c4cf
>> --- /dev/null
>> +++ b/drivers/i2c/busses/i2c-xiic.c
>> @@ -0,0 +1,802 @@
>> +/*
>> + * i2c-xiic.c
> 
> the directory path to the file would have been nice.

Will update

> 
>> + * Copyright (c) 2009 Intel Corporation
> 
> is this right, you've not got an @intel.com address?

It's correct.

> 
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program; if not, write to the Free Software
>> + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>> + */
>> +
>> +/* Supports:
>> + * Xilinx IIC
>> + */
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/init.h>
>> +#include <linux/errno.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/i2c.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/wait.h>
>> +#include <linux/i2c-xiic.h>
>> +#include <linux/io.h>
>> +
>> +#define DRIVER_NAME "xiic-i2c"
>> +
>> +enum xilinx_i2c_state {
>> +	STATE_DONE,
>> +	STATE_ERROR,
>> +	STATE_START
>> +};
>> +
>> +struct xiic_i2c {
>> +	void __iomem		*base;	/* Memory base of the HW registers */
>> +	wait_queue_head_t	wait;	/* wait queue for callers */
>> +	struct i2c_adapter	adap;	/* kernel adapter representation */
>> +	struct i2c_msg		*tx_msg;/* Messages from above to send */
>> +	spinlock_t		lock;	/* mutual exclusion */
>> +	unsigned int 		tx_pos;	/* Current pos in TX message */
>> +	unsigned int		nmsgs;	/* number of messages in tx_msg */
>> +	enum xilinx_i2c_state	state;	/* see STATE_ */
>> +	struct i2c_msg		*rx_msg;/* current RX message */
>> +	int			rx_pos;	/* position within current RX message */
>> +};
> 
> I'd much rather see this kernel-doced.

Good idea, will update.

> 
>> +
>> +#define XIIC_MSB_OFFSET 0
>> +#define XIIC_REG_OFFSET (0x100+XIIC_MSB_OFFSET)
> 
> givevn you're running everything through indirect read/write calls,
> how about doing it in there?

Could do, bad thing is that it would add in an addition during runtime
rather than having the C preprocessor doing it.

I think I would like to leave it as is.

What do you think?

> 
>> +/*
>> + * Register offsets in bytes from RegisterBase. Three is added to the
>> + * base offset to access LSB (IBM style) of the word
>> + */
>> +#define XIIC_CR_REG_OFFSET   (0x00+XIIC_REG_OFFSET)	/* Control Register   */
>> +#define XIIC_SR_REG_OFFSET   (0x04+XIIC_REG_OFFSET)	/* Status Register    */
>> +#define XIIC_DTR_REG_OFFSET  (0x08+XIIC_REG_OFFSET)	/* Data Tx Register   */
>> +#define XIIC_DRR_REG_OFFSET  (0x0C+XIIC_REG_OFFSET)	/* Data Rx Register   */
>> +#define XIIC_ADR_REG_OFFSET  (0x10+XIIC_REG_OFFSET)	/* Address Register   */
>> +#define XIIC_TFO_REG_OFFSET  (0x14+XIIC_REG_OFFSET)	/* Tx FIFO Occupancy  */
>> +#define XIIC_RFO_REG_OFFSET  (0x18+XIIC_REG_OFFSET)	/* Rx FIFO Occupancy  */
>> +#define XIIC_TBA_REG_OFFSET  (0x1C+XIIC_REG_OFFSET)	/* 10 Bit Address reg */
>> +#define XIIC_RFD_REG_OFFSET  (0x20+XIIC_REG_OFFSET)	/* Rx FIFO Depth reg  */
>> +#define XIIC_GPO_REG_OFFSET  (0x24+XIIC_REG_OFFSET)	/* Output Register    */
>> +
>> +/* Control Register masks */
>> +#define XIIC_CR_ENABLE_DEVICE_MASK        0x01	/* Device enable = 1      */
>> +#define XIIC_CR_TX_FIFO_RESET_MASK        0x02	/* Transmit FIFO reset=1  */
>> +#define XIIC_CR_MSMS_MASK                 0x04	/* Master starts Txing=1  */
>> +#define XIIC_CR_DIR_IS_TX_MASK            0x08	/* Dir of tx. Txing=1     */
>> +#define XIIC_CR_NO_ACK_MASK               0x10	/* Tx Ack. NO ack = 1     */
>> +#define XIIC_CR_REPEATED_START_MASK       0x20	/* Repeated start = 1     */
>> +#define XIIC_CR_GENERAL_CALL_MASK         0x40	/* Gen Call enabled = 1   */
>> +
>> +/* Status Register masks */
>> +#define XIIC_SR_GEN_CALL_MASK             0x01	/* 1=a mstr issued a GC   */
>> +#define XIIC_SR_ADDR_AS_SLAVE_MASK        0x02	/* 1=when addr as slave   */
>> +#define XIIC_SR_BUS_BUSY_MASK             0x04	/* 1 = bus is busy        */
>> +#define XIIC_SR_MSTR_RDING_SLAVE_MASK     0x08	/* 1=Dir: mstr <-- slave  */
>> +#define XIIC_SR_TX_FIFO_FULL_MASK         0x10	/* 1 = Tx FIFO full       */
>> +#define XIIC_SR_RX_FIFO_FULL_MASK         0x20	/* 1 = Rx FIFO full       */
>> +#define XIIC_SR_RX_FIFO_EMPTY_MASK        0x40	/* 1 = Rx FIFO empty      */
>> +#define XIIC_SR_TX_FIFO_EMPTY_MASK        0x80	/* 1 = Tx FIFO empty      */
>> +
>> +/* Interrupt Status Register masks    Interrupt occurs when...       */
>> +#define XIIC_INTR_ARB_LOST_MASK           0x01	/* 1 = arbitration lost   */
>> +#define XIIC_INTR_TX_ERROR_MASK           0x02	/* 1=Tx error/msg complete */
>> +#define XIIC_INTR_TX_EMPTY_MASK           0x04	/* 1 = Tx FIFO/reg empty  */
>> +#define XIIC_INTR_RX_FULL_MASK            0x08	/* 1=Rx FIFO/reg=OCY level */
>> +#define XIIC_INTR_BNB_MASK                0x10	/* 1 = Bus not busy       */
>> +#define XIIC_INTR_AAS_MASK                0x20	/* 1 = when addr as slave */
>> +#define XIIC_INTR_NAAS_MASK               0x40	/* 1 = not addr as slave  */
>> +#define XIIC_INTR_TX_HALF_MASK            0x80	/* 1 = TX FIFO half empty */
>> +
>> +/* The following constants specify the depth of the FIFOs */
>> +#define IIC_RX_FIFO_DEPTH         16	/* Rx fifo capacity               */
>> +#define IIC_TX_FIFO_DEPTH         16	/* Tx fifo capacity               */
>> +
>> +/* The following constants specify groups of interrupts that are typically
>> + * enabled or disables at the same time
>> + */
>> +#define XIIC_TX_INTERRUPTS                           \
>> +(XIIC_INTR_TX_ERROR_MASK | XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK)
>> +
>> +#define XIIC_TX_RX_INTERRUPTS (XIIC_INTR_RX_FULL_MASK | XIIC_TX_INTERRUPTS)
>> +
>> +/* The following constants are used with the following macros to specify the
>> + * operation, a read or write operation.
>> + */
>> +#define XIIC_READ_OPERATION  1
>> +#define XIIC_WRITE_OPERATION 0
>> +
>> +/*
>> + * Tx Fifo upper bit masks.
>> + */
>> +#define XIIC_TX_DYN_START_MASK            0x0100 /* 1 = Set dynamic start */
>> +#define XIIC_TX_DYN_STOP_MASK             0x0200 /* 1 = Set dynamic stop */
>> +
>> +/*
>> + * The following constants define the register offsets for the Interrupt
>> + * registers. There are some holes in the memory map for reserved addresses
>> + * to allow other registers to be added and still match the memory map of the
>> + * interrupt controller registers
>> + */
>> +#define XIIC_DGIER_OFFSET    0x1C /* Device Global Interrupt Enable Register */
>> +#define XIIC_IISR_OFFSET     0x20 /* Interrupt Status Register */
>> +#define XIIC_IIER_OFFSET     0x28 /* Interrupt Enable Register */
>> +#define XIIC_RESETR_OFFSET   0x40 /* Reset Register */
>> +
>> +#define XIIC_RESET_MASK             0xAUL
>> +
>> +/*
>> + * The following constant is used for the device global interrupt enable
>> + * register, to enable all interrupts for the device, this is the only bit
>> + * in the register
>> + */
>> +#define XIIC_GINTR_ENABLE_MASK      0x80000000UL
>> +
>> +#define xiic_tx_space(i2c) ((i2c)->tx_msg->len - (i2c)->tx_pos)
>> +#define xiic_rx_space(i2c) ((i2c)->rx_msg->len - (i2c)->rx_pos)
>> +
>> +static void xiic_start_xfer(struct xiic_i2c *i2c);
>> +static void __xiic_start_xfer(struct xiic_i2c *i2c);
>> +
>> +static inline void xiic_setreg8(struct xiic_i2c *i2c, int reg, u8 value)
>> +{
>> +	iowrite8(value, i2c->base + reg);
>> +}
>> +
>> +static inline u8 xiic_getreg8(struct xiic_i2c *i2c, int reg)
>> +{
>> +	return ioread8(i2c->base + reg);
>> +}
>> +
>> +static inline void xiic_setreg16(struct xiic_i2c *i2c, int reg, u16 value)
>> +{
>> +	iowrite16(value, i2c->base + reg);
>> +}
>> +
>> +static inline void xiic_setreg32(struct xiic_i2c *i2c, int reg, int value)
>> +{
>> +	iowrite32(value, i2c->base + reg);
>> +}
>> +
>> +static inline int xiic_getreg32(struct xiic_i2c *i2c, int reg)
>> +{
>> +	return ioread32(i2c->base + reg);
>> +}
>> +
>> +static inline void xiic_irq_dis(struct xiic_i2c *i2c, u32 mask)
>> +{
>> +	u32 ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
>> +	xiic_setreg32(i2c, XIIC_IIER_OFFSET, ier & ~mask);
>> +}
>> +
>> +static inline void xiic_irq_en(struct xiic_i2c *i2c, u32 mask)
>> +{
>> +	u32 ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
>> +	xiic_setreg32(i2c, XIIC_IIER_OFFSET, ier | mask);
>> +}
>> +
>> +static inline void xiic_irq_clr(struct xiic_i2c *i2c, u32 mask)
>> +{
>> +	u32 isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
>> +	xiic_setreg32(i2c, XIIC_IISR_OFFSET, isr & mask);
>> +}
>> +
>> +static inline void xiic_irq_clr_en(struct xiic_i2c *i2c, u32 mask)
>> +{
>> +	xiic_irq_clr(i2c, mask);
>> +	xiic_irq_en(i2c, mask);
>> +}
>> +
>> +static void xiic_clear_rx_fifo(struct xiic_i2c *i2c)
>> +{
>> +	u8 sr;
>> +	for (sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET);
>> +		!(sr & XIIC_SR_RX_FIFO_EMPTY_MASK);
>> +		sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET))
>> +		xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);
>> +}
>> +
>> +static void xiic_reinit(struct xiic_i2c *i2c)
>> +{
>> +	xiic_setreg32(i2c, XIIC_RESETR_OFFSET, XIIC_RESET_MASK);
>> +
>> +	/* Set receive Fifo depth to maximum (zero based). */
>> +	xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, IIC_RX_FIFO_DEPTH - 1);
>> +
>> +	/* Reset Tx Fifo. */
>> +	xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_TX_FIFO_RESET_MASK);
>> +
>> +	/* Enable IIC Device, remove Tx Fifo reset & disable general call. */
>> +	xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_ENABLE_DEVICE_MASK);
>> +
>> +	/* make sure RX fifo is empty */
>> +	xiic_clear_rx_fifo(i2c);
>> +
>> +	/* Enable interrupts */
>> +	xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
>> +
>> +	xiic_irq_clr_en(i2c, XIIC_INTR_AAS_MASK | XIIC_INTR_ARB_LOST_MASK);
>> +}
>> +
>> +static void xiic_deinit(struct xiic_i2c *i2c)
>> +{
>> +	u8 cr;
>> +
>> +	xiic_setreg32(i2c, XIIC_RESETR_OFFSET, XIIC_RESET_MASK);
>> +
>> +	/* Disable IIC Device. */
>> +	cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
>> +	xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr & ~XIIC_CR_ENABLE_DEVICE_MASK);
>> +}
>> +
>> +static void xiic_read_rx(struct xiic_i2c *i2c)
>> +{
>> +	u8 bytes_in_fifo;
>> +	int i;
>> +
>> +	bytes_in_fifo = xiic_getreg8(i2c, XIIC_RFO_REG_OFFSET) + 1;
>> +
>> +	dev_dbg(i2c->adap.dev.parent, "%s entry, bytes in fifo: %d, msg: %d"
>> +		", SR: 0x%x, CR: 0x%x\n",
>> +		__func__, bytes_in_fifo, xiic_rx_space(i2c),
>> +		xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
>> +		xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
>> +
>> +	if (bytes_in_fifo > xiic_rx_space(i2c))
>> +		bytes_in_fifo = xiic_rx_space(i2c);
>> +
>> +	for (i = 0; i < bytes_in_fifo; i++)
>> +		i2c->rx_msg->buf[i2c->rx_pos++] =
>> +			xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);
>> +
>> +	xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET,
>> +		(xiic_rx_space(i2c) > IIC_RX_FIFO_DEPTH) ?
>> +		IIC_RX_FIFO_DEPTH - 1 :  xiic_rx_space(i2c) - 1);
>> +}
>> +
>> +static int xiic_tx_fifo_space(struct xiic_i2c *i2c)
>> +{
>> +	/* return the actual space left in the FIFO */
>> +	return IIC_TX_FIFO_DEPTH - xiic_getreg8(i2c, XIIC_TFO_REG_OFFSET) - 1;
>> +}
>> +
>> +static void xiic_fill_tx_fifo(struct xiic_i2c *i2c)
>> +{
>> +	u8 fifo_space = xiic_tx_fifo_space(i2c);
>> +	int len = xiic_tx_space(i2c);
>> +
>> +	len = (len > fifo_space) ? fifo_space : len;
>> +
>> +	dev_dbg(i2c->adap.dev.parent, "%s entry, len: %d, fifo space: %d\n",
>> +		__func__, len, fifo_space);
>> +
>> +	while (len--) {
>> +		u16 data = i2c->tx_msg->buf[i2c->tx_pos++];
>> +		if ((xiic_tx_space(i2c) == 0) && (i2c->nmsgs == 1)) {
>> +			/* last message in transfer -> STOP */
>> +			data |= XIIC_TX_DYN_STOP_MASK;
>> +			dev_dbg(i2c->adap.dev.parent, "%s TX STOP\n", __func__);
>> +
>> +			xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
>> +		} else
>> +			xiic_setreg8(i2c, XIIC_DTR_REG_OFFSET, data);
>> +	}
>> +}
>> +
>> +static void xiic_wakeup(struct xiic_i2c *i2c, int code)
>> +{
>> +	i2c->tx_msg = NULL;
>> +	i2c->rx_msg = NULL;
>> +	i2c->nmsgs = 0;
>> +	i2c->state = code;
>> +	wake_up(&i2c->wait);
>> +}
>> +
>> +static void xiic_process(struct xiic_i2c *i2c)
>> +{
>> +	u32 pend, isr, ier;
>> +	u32 clr = 0;
>> +
>> +	/* Get the interrupt Status from the IPIF. There is no clearing of
>> +	 * interrupts in the IPIF. Interrupts must be cleared at the source.
>> +	 * To find which interrupts are pending; AND interrupts pending with
>> +	 * interrupts masked.
>> +	 */
>> +	isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
>> +	ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
>> +	pend = isr & ier;
>> +
>> +	dev_dbg(i2c->adap.dev.parent, "%s entry, IER: 0x%x, ISR: 0x%x, "
>> +		"pend: 0x%x, SR: 0x%x, msg: %p, nmsgs: %d\n",
>> +		__func__, ier, isr, pend, xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
>> +		i2c->tx_msg, i2c->nmsgs);
>> +
>> +	/* Do not processes a devices interrupts if the device has no
>> +	 * interrupts pending
>> +	 */
>> +	if (!pend)
>> +		return;
>> +
>> +	/* Service requesting interrupt */
>> +	if ((pend & XIIC_INTR_ARB_LOST_MASK) ||
>> +		((pend & XIIC_INTR_TX_ERROR_MASK) &&
>> +		!(pend & XIIC_INTR_RX_FULL_MASK))) {
>> +		/* bus arbritration lost, or...
>> +		 * Transmit error _OR_ RX completed
>> +		 * if this happens when RX_FULL is not set
>> +		 * this is probably a TX error
>> +		 */
>> +
>> +		dev_dbg(i2c->adap.dev.parent, "%s error\n", __func__);
>> +
>> +		/* dynamic mode seem to suffer from problems if we just flushes
>> +		 * fifos and the next message is a TX with len 0 (only addr)
>> +		 * reset the IP instead of just flush fifos
>> +		 */
>> +		xiic_reinit(i2c);
>> +
>> +		if (i2c->tx_msg)
>> +			xiic_wakeup(i2c, STATE_ERROR);
>> +
>> +	} else if (pend & XIIC_INTR_RX_FULL_MASK) {
>> +		/* Receive register/FIFO is full */
>> +
>> +		clr = XIIC_INTR_RX_FULL_MASK;
>> +		if (!i2c->rx_msg) {
>> +			dev_dbg(i2c->adap.dev.parent,
>> +				"%s unexpexted RX IRQ\n", __func__);
>> +			xiic_clear_rx_fifo(i2c);
>> +			goto out;
>> +		}
>> +
>> +		xiic_read_rx(i2c);
>> +		if (xiic_rx_space(i2c) == 0) {
>> +			/* this is the last part of the message */
>> +			i2c->rx_msg = NULL;
>> +
>> +			/* also clear TX error if there (RX complete) */
>> +			clr |= (isr & XIIC_INTR_TX_ERROR_MASK);
>> +
>> +			dev_dbg(i2c->adap.dev.parent,
>> +				"%s end of message, nmsgs: %d\n",
>> +				__func__, i2c->nmsgs);
>> +
>> +			/* send next message if this wasn't the last,
>> +			 * otherwise the transfer will be finialise when
>> +			 * receiving the bus not busy interrupt
>> +			 */
>> +			if (i2c->nmsgs > 1) {
>> +				i2c->nmsgs--;
>> +				i2c->tx_msg++;
>> +				dev_dbg(i2c->adap.dev.parent,
>> +					"%s will start next...\n", __func__);
>> +
>> +				__xiic_start_xfer(i2c);
>> +			}
>> +		}
>> +	} else if (pend & XIIC_INTR_BNB_MASK) {
>> +		/* IIC bus has transitioned to not busy */
>> +		clr = XIIC_INTR_BNB_MASK;
>> +
>> +		/* The bus is not busy, disable BusNotBusy interrupt */
>> +		xiic_irq_dis(i2c, XIIC_INTR_BNB_MASK);
>> +
>> +		if (!i2c->tx_msg)
>> +			goto out;
>> +
>> +		if ((i2c->nmsgs == 1) && !i2c->rx_msg &&
>> +			xiic_tx_space(i2c) == 0)
>> +			xiic_wakeup(i2c, STATE_DONE);
>> +		else
>> +			xiic_wakeup(i2c, STATE_ERROR);
>> +
>> +	} else if (pend & (XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK)) {
>> +		/* Transmit register/FIFO is empty or ? empty */
>> +
>> +		clr = pend &
>> +			(XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK);
>> +
>> +		if (!i2c->tx_msg) {
>> +			dev_dbg(i2c->adap.dev.parent,
>> +				"%s unexpexted TX IRQ\n", __func__);
>> +			goto out;
>> +		}
>> +
>> +		xiic_fill_tx_fifo(i2c);
>> +
>> +		/* current message sent and there is space in the fifo */
>> +		if (!xiic_tx_space(i2c) && xiic_tx_fifo_space(i2c) >= 2) {
>> +			dev_dbg(i2c->adap.dev.parent,
>> +				"%s end of message sent, nmsgs: %d\n",
>> +				__func__, i2c->nmsgs);
>> +			if (i2c->nmsgs > 1) {
>> +				i2c->nmsgs--;
>> +				i2c->tx_msg++;
>> +				__xiic_start_xfer(i2c);
>> +			} else {
>> +				xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
>> +
>> +				dev_err(i2c->adap.dev.parent,
>> +					"%s Got TX IRQ but no more to do...\n",
>> +					__func__);
>> +			}
>> +		} else if (!xiic_tx_space(i2c) && (i2c->nmsgs == 1))
>> +			/* current frame is sent and is last,
>> +			 * make sure to disable tx half
>> +			 */
>> +			xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
>> +	} else {
>> +		/* got IRQ which is not acked */
>> +		dev_err(i2c->adap.dev.parent, "%s Got unexpected IRQ\n",
>> +			__func__);
>> +		clr = pend;
>> +	}
>> +out:
>> +	dev_dbg(i2c->adap.dev.parent, "%s clr: 0x%x\n", __func__, clr);
>> +
>> +	xiic_setreg32(i2c, XIIC_IISR_OFFSET, clr);
>> +}
>> +
>> +static int xiic_bus_busy(struct xiic_i2c *i2c)
>> +{
>> +	u8 sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET);
>> +
>> +	return (sr & XIIC_SR_BUS_BUSY_MASK) ? -EBUSY : 0;
>> +}
>> +
>> +static int xiic_busy(struct xiic_i2c *i2c)
>> +{
>> +	int tries = 3;
>> +	int err;
>> +
>> +	if (i2c->tx_msg)
>> +		return -EBUSY;
>> +
>> +	/* for instance if previous transfer was terminated due to TX error
>> +	 * it might be that the bus is on it's way to become available
>> +	 * give it at most 3 ms to wake
>> +	 */
>> +	err = xiic_bus_busy(i2c);
>> +	while (err && tries--) {
>> +		mdelay(1);
>> +		err = xiic_bus_busy(i2c);
>> +	}
>> +
>> +	return err;
>> +}
>> +
>> +static void xiic_start_recv(struct xiic_i2c *i2c)
>> +{
>> +	u8 rx_watermark;
>> +	struct i2c_msg *msg = i2c->rx_msg = i2c->tx_msg;
>> +
>> +	/* Clear and enable Rx full interrupt. */
>> +	xiic_irq_clr_en(i2c, XIIC_INTR_RX_FULL_MASK | XIIC_INTR_TX_ERROR_MASK);
>> +
>> +	/* we want to get all but last byte, because the TX_ERROR IRQ is used
>> +	 * to inidicate error ACK on the address, and negative ack on the last
>> +	 * received byte, so to not mix them receive all but last.
>> +	 * In the case where there is only one byte to receive
>> +	 * we can check if ERROR and RX full is set at the same time
>> +	 */
>> +	rx_watermark = msg->len;
>> +	if (rx_watermark > IIC_RX_FIFO_DEPTH)
>> +		rx_watermark = IIC_RX_FIFO_DEPTH;
>> +	xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, rx_watermark - 1);
>> +
>> +	if (!(msg->flags & I2C_M_NOSTART))
>> +		/* write the address */
>> +		xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET,
>> +			(msg->addr << 1) | XIIC_READ_OPERATION |
>> +			XIIC_TX_DYN_START_MASK);
>> +
>> +	xiic_irq_clr_en(i2c, XIIC_INTR_BNB_MASK);
>> +
>> +	xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET,
>> +		msg->len | ((i2c->nmsgs == 1) ? XIIC_TX_DYN_STOP_MASK : 0));
>> +	if (i2c->nmsgs == 1)
>> +		/* very last, enable bus not busy as well */
>> +		xiic_irq_clr_en(i2c, XIIC_INTR_BNB_MASK);
>> +
>> +	/* the message is tx:ed */
>> +	i2c->tx_pos = msg->len;
>> +}
>> +
>> +static void xiic_start_send(struct xiic_i2c *i2c)
>> +{
>> +	struct i2c_msg *msg = i2c->tx_msg;
>> +
>> +	xiic_irq_clr(i2c, XIIC_INTR_TX_ERROR_MASK);
>> +
>> +	dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, len: %d, "
>> +		"ISR: 0x%x, CR: 0x%x\n",
>> +		__func__, msg, msg->len, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
>> +		xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
>> +
>> +	if (!(msg->flags & I2C_M_NOSTART)) {
>> +		/* write the address */
>> +		u16 data = ((msg->addr << 1) & 0xfe) | XIIC_WRITE_OPERATION |
>> +			XIIC_TX_DYN_START_MASK;
>> +		if ((i2c->nmsgs == 1) && msg->len == 0)
>> +			/* no data and last message -> add STOP */
>> +			data |= XIIC_TX_DYN_STOP_MASK;
>> +
>> +		xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
>> +	}
>> +
>> +	xiic_fill_tx_fifo(i2c);
>> +
>> +	/* Clear any pending Tx empty, Tx Error and then enable them. */
>> +	xiic_irq_clr_en(i2c, XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_ERROR_MASK |
>> +		XIIC_INTR_BNB_MASK);
>> +}
>> +
>> +static irqreturn_t xiic_isr(int irq, void *dev_id)
>> +{
>> +	struct xiic_i2c *i2c = dev_id;
>> +
>> +	spin_lock(&i2c->lock);
>> +	/* disable interrupts globally */
>> +	xiic_setreg32(i2c, XIIC_DGIER_OFFSET, 0);
>> +
>> +	dev_dbg(i2c->adap.dev.parent, "%s entry\n", __func__);
>> +
>> +	xiic_process(i2c);
>> +
>> +	xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
>> +	spin_unlock(&i2c->lock);
>> +
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static void __xiic_start_xfer(struct xiic_i2c *i2c)
>> +{
>> +	int first = 1;
>> +	int fifo_space = xiic_tx_fifo_space(i2c);
>> +	dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, fifos space: %d\n",
>> +		__func__, i2c->tx_msg, fifo_space);
>> +
>> +	if (!i2c->tx_msg)
>> +		return;
>> +
>> +	i2c->rx_pos = 0;
>> +	i2c->tx_pos = 0;
>> +	i2c->state = STATE_START;
>> +	while ((fifo_space >= 2) && (first || (i2c->nmsgs > 1))) {
>> +		if (!first) {
>> +			i2c->nmsgs--;
>> +			i2c->tx_msg++;
>> +			i2c->tx_pos = 0;
>> +		} else
>> +			first = 0;
>> +
>> +		if (i2c->tx_msg->flags & I2C_M_RD) {
>> +			/* we dont date putting several reads in the FIFO */
>> +			xiic_start_recv(i2c);
>> +			return;
>> +		} else {
>> +			xiic_start_send(i2c);
>> +			if (xiic_tx_space(i2c) != 0) {
>> +				/* the message could not be completely sent */
>> +				break;
>> +			}
>> +		}
>> +
>> +		fifo_space = xiic_tx_fifo_space(i2c);
>> +	}
>> +
>> +	/* there are more messages or the current one could not be completely
>> +	 * put into the FIFO, also enable the half empty interrupt
>> +	 */
>> +	if (i2c->nmsgs > 1 || xiic_tx_space(i2c))
>> +		xiic_irq_clr_en(i2c, XIIC_INTR_TX_HALF_MASK);
>> +
>> +}
>> +
>> +static void xiic_start_xfer(struct xiic_i2c *i2c)
>> +{
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&i2c->lock, flags);
>> +	xiic_reinit(i2c);
>> +	/* disable interrupts globally */
>> +	xiic_setreg32(i2c, XIIC_DGIER_OFFSET, 0);
>> +	spin_unlock_irqrestore(&i2c->lock, flags);
>> +
>> +	__xiic_start_xfer(i2c);
>> +	xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
>> +}
>> +
>> +static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>> +{
>> +	struct xiic_i2c *i2c = i2c_get_adapdata(adap);
>> +	int err;
>> +
>> +	dev_dbg(adap->dev.parent, "%s entry SR: 0x%x\n", __func__,
>> +		xiic_getreg8(i2c, XIIC_SR_REG_OFFSET));
>> +
>> +	err = xiic_busy(i2c);
>> +	if (err)
>> +		return err;
>> +
>> +	i2c->tx_msg = msgs;
>> +	i2c->nmsgs = num;
>> +
>> +	xiic_start_xfer(i2c);
>> +
>> +	if (wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) ||
>> +		(i2c->state == STATE_DONE), HZ))
>> +		return (i2c->state == STATE_DONE) ? num : -EIO;
>> +	else {
>> +		i2c->tx_msg = NULL;
>> +		i2c->rx_msg = NULL;
>> +		i2c->nmsgs = 0;
>> +		return -ETIMEDOUT;
>> +	}
>> +}
>> +
>> +static u32 xiic_func(struct i2c_adapter *adap)
>> +{
>> +	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
>> +}
>> +
>> +static const struct i2c_algorithm xiic_algorithm = {
>> +	.master_xfer	= xiic_xfer,
>> +	.functionality	= xiic_func,
>> +};
>> +
>> +static struct i2c_adapter xiic_adapter = {
>> +	.owner		= THIS_MODULE,
>> +	.name		= DRIVER_NAME,
>> +	.class		= I2C_CLASS_HWMON | I2C_CLASS_SPD,
>> +	.algo		= &xiic_algorithm,
>> +};
>> +
>> +
>> +static int __devinit xiic_i2c_probe(struct platform_device *pdev)
>> +{
>> +	struct xiic_i2c *i2c;
>> +	struct xiic_i2c_platform_data *pdata;
>> +	struct resource *res;
>> +	int ret, irq;
>> +	u8 i;
>> +
>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	if (!res)
>> +		goto resource_missing;
>> +
>> +	irq = platform_get_irq(pdev, 0);
>> +	if (irq < 0)
>> +		goto resource_missing;
>> +
>> +	pdata = (struct xiic_i2c_platform_data *) pdev->dev.platform_data;
>> +	if (!pdata)
>> +		return -EINVAL;
>> +
>> +	i2c = kzalloc(sizeof(*i2c), GFP_KERNEL);
>> +	if (!i2c)
>> +		return -ENOMEM;
>> +
>> +	if (!request_mem_region(res->start, resource_size(res), pdev->name)) {
>> +		dev_err(&pdev->dev, "Memory region busy\n");
>> +		ret = -EBUSY;
>> +		goto request_mem_failed;
>> +	}
>> +
>> +	i2c->base = ioremap(res->start, resource_size(res));
>> +	if (!i2c->base) {
>> +		dev_err(&pdev->dev, "Unable to map registers\n");
>> +		ret = -EIO;
>> +		goto map_failed;
>> +	}
>> +
>> +	/* hook up driver to tree */
>> +	platform_set_drvdata(pdev, i2c);
>> +	i2c->adap = xiic_adapter;
>> +	i2c_set_adapdata(&i2c->adap, i2c);
>> +	i2c->adap.dev.parent = &pdev->dev;
>> +
>> +	xiic_reinit(i2c);
>> +
>> +	spin_lock_init(&i2c->lock);
>> +	init_waitqueue_head(&i2c->wait);
>> +	ret = request_irq(irq, xiic_isr, 0, pdev->name, i2c);
>> +	if (ret) {
>> +		dev_err(&pdev->dev, "Cannot claim IRQ\n");
>> +		goto request_irq_failed;
>> +	}
>> +
>> +	/* add i2c adapter to i2c tree */
>> +	ret = i2c_add_adapter(&i2c->adap);
>> +	if (ret) {
>> +		dev_err(&pdev->dev, "Failed to add adapter\n");
>> +		goto add_adapter_failed;
>> +	}
>> +
>> +	/* add in known devices to the bus */
>> +	for (i = 0; i < pdata->num_devices; i++)
>> +		i2c_new_device(&i2c->adap, pdata->devices + i);
> 
> wouldn't i2c_register_board_info() do the job for you too?

No actually not, we had a discussion about this like 6-9 months ago,
when I posted the similar solution as a patch to ocores. Problem is that
we don't know the bus number in advance and in theory several boards
containing the I2C bus could in theory show up.
I would like to see the same solution here.

> 
>> +	return 0;
>> +
>> +add_adapter_failed:
>> +	free_irq(irq, i2c);
>> +request_irq_failed:
>> +	xiic_deinit(i2c);
>> +	iounmap(i2c->base);
>> +map_failed:
>> +	release_mem_region(res->start, resource_size(res));
>> +request_mem_failed:
>> +	kfree(i2c);
>> +
>> +	return ret;
>> +resource_missing:
>> +	dev_err(&pdev->dev, "IRQ or Memory resource is missing\n");
>> +	return -ENOENT;
>> +}
>> +
>> +static int __devexit xiic_i2c_remove(struct platform_device* pdev)
>> +{
>> +	struct xiic_i2c *i2c = platform_get_drvdata(pdev);
>> +	struct resource *res;
>> +
>> +	/* remove adapter & data */
>> +	i2c_del_adapter(&i2c->adap);
>> +
>> +	xiic_deinit(i2c);
>> +
>> +	platform_set_drvdata(pdev, NULL);
>> +
>> +	free_irq(platform_get_irq(pdev, 0), i2c);
>> +
>> +	iounmap(i2c->base);
>> +
>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	if (res)
>> +		release_mem_region(res->start, resource_size(res));
>> +
>> +	kfree(i2c);
>> +
>> +	return 0;
>> +}
>> +
>> +
>> +/* work with hotplug and coldplug */
>> +MODULE_ALIAS("platform:"DRIVER_NAME);
>> +
>> +static struct platform_driver xiic_i2c_driver = {
>> +	.probe   = xiic_i2c_probe,
>> +	.remove  = __devexit_p(xiic_i2c_remove),
>> +	.driver  = {
>> +		.owner = THIS_MODULE,
>> +		.name = DRIVER_NAME,
>> +	},
>> +};
>> +
>> +static int __init xiic_i2c_init(void)
>> +{
>> +	return platform_driver_register(&xiic_i2c_driver);
>> +}
>> +
>> +static void __exit xiic_i2c_exit(void)
>> +{
>> +	platform_driver_unregister(&xiic_i2c_driver);
>> +}
>> +
>> +module_init(xiic_i2c_init);
>> +module_exit(xiic_i2c_exit);
>> +
>> +MODULE_AUTHOR("info-l7gf1WXxx3uGw+nKnLezzg@public.gmane.org");
>> +MODULE_DESCRIPTION("Xilinx I2C bus driver");
>> +MODULE_LICENSE("GPL v2");
>> diff --git a/include/linux/i2c-xiic.h b/include/linux/i2c-xiic.h
>> new file mode 100644
>> index 0000000..4f9f225
>> --- /dev/null
>> +++ b/include/linux/i2c-xiic.h
>> @@ -0,0 +1,43 @@
>> +/*
>> + * i2c-xiic.h
>> + * Copyright (c) 2009 Intel Corporation
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program; if not, write to the Free Software
>> + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>> + */
>> +
>> +/* Supports:
>> + * Xilinx IIC
>> + */
>> +
>> +#ifndef _LINUX_I2C_XIIC_H
>> +#define _LINUX_I2C_XIIC_H
>> +
>> +/**
>> + * struct xiic_i2c_platform_data - Platform data of the Xilinx I2C driver
>> + * @num_devices:	Number of devices that shall be added when the driver
>> + *			is probed.
>> + * @devices:		The actuall devices to add.
>> + *
>> + * This purpose of this platform data struct is to be able to provide a number
>> + * of devices that should be added to the I2C bus. The reason is that sometimes
>> + * the I2C board info is not enough, a new PCI board can for instance be
>> + * plugged into a standard PC, and the bus number might be unknown at
>> + * early init time.
>> + */
>> +struct xiic_i2c_platform_data {
>> +	u8				num_devices;
>> +	struct i2c_board_info const	*devices;
>> +};
>> +
>> +#endif /* _LINUX_I2C_XIIC_H */
>>
>> --
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>