drivers/spi/xilinx_spi.c - maze/linux - Git at Google

 /*
  * xilinx_spi.c
  *
  * Xilinx SPI controller driver (master mode only)
  *
  * Author: MontaVista Software, Inc.
  *	source@mvista.com
  *
  * 2002-2007 (c) MontaVista Software, Inc.  This file is licensed under the
  * terms of the GNU General Public License version 2.  This program is licensed
  * "as is" without any warranty of any kind, whether express or implied.
  */

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/platform_device.h>

 #include <linux/of_platform.h>
 #include <linux/of_device.h>
 #include <linux/of_spi.h>

 #include <linux/spi/spi.h>
 #include <linux/spi/spi_bitbang.h>
 #include <linux/io.h>

 #define XILINX_SPI_NAME "xilinx_spi"

 /* Register definitions as per "OPB Serial Peripheral Interface (SPI) (v1.00e)
  * Product Specification", DS464
  */
 #define XSPI_CR_OFFSET		0x62	/* 16-bit Control Register */

 #define XSPI_CR_ENABLE		0x02
 #define XSPI_CR_MASTER_MODE	0x04
 #define XSPI_CR_CPOL		0x08
 #define XSPI_CR_CPHA		0x10
 #define XSPI_CR_MODE_MASK	(XSPI_CR_CPHA | XSPI_CR_CPOL)
 #define XSPI_CR_TXFIFO_RESET	0x20
 #define XSPI_CR_RXFIFO_RESET	0x40
 #define XSPI_CR_MANUAL_SSELECT	0x80
 #define XSPI_CR_TRANS_INHIBIT	0x100

 #define XSPI_SR_OFFSET		0x67	/* 8-bit Status Register */

 #define XSPI_SR_RX_EMPTY_MASK	0x01	/* Receive FIFO is empty */
 #define XSPI_SR_RX_FULL_MASK	0x02	/* Receive FIFO is full */
 #define XSPI_SR_TX_EMPTY_MASK	0x04	/* Transmit FIFO is empty */
 #define XSPI_SR_TX_FULL_MASK	0x08	/* Transmit FIFO is full */
 #define XSPI_SR_MODE_FAULT_MASK	0x10	/* Mode fault error */

 #define XSPI_TXD_OFFSET		0x6b	/* 8-bit Data Transmit Register */
 #define XSPI_RXD_OFFSET		0x6f	/* 8-bit Data Receive Register */

 #define XSPI_SSR_OFFSET		0x70	/* 32-bit Slave Select Register */

 /* Register definitions as per "OPB IPIF (v3.01c) Product Specification", DS414
  * IPIF registers are 32 bit
  */
 #define XIPIF_V123B_DGIER_OFFSET	0x1c	/* IPIF global int enable reg */
 #define XIPIF_V123B_GINTR_ENABLE	0x80000000

 #define XIPIF_V123B_IISR_OFFSET		0x20	/* IPIF interrupt status reg */
 #define XIPIF_V123B_IIER_OFFSET		0x28	/* IPIF interrupt enable reg */

 #define XSPI_INTR_MODE_FAULT		0x01	/* Mode fault error */
 #define XSPI_INTR_SLAVE_MODE_FAULT	0x02	/* Selected as slave while
 						 * disabled */
 #define XSPI_INTR_TX_EMPTY		0x04	/* TxFIFO is empty */
 #define XSPI_INTR_TX_UNDERRUN		0x08	/* TxFIFO was underrun */
 #define XSPI_INTR_RX_FULL		0x10	/* RxFIFO is full */
 #define XSPI_INTR_RX_OVERRUN		0x20	/* RxFIFO was overrun */

 #define XIPIF_V123B_RESETR_OFFSET	0x40	/* IPIF reset register */
 #define XIPIF_V123B_RESET_MASK		0x0a	/* the value to write */

 struct xilinx_spi {
 	/* bitbang has to be first */
 	struct spi_bitbang bitbang;
 	struct completion done;

 	void __iomem	*regs;	/* virt. address of the control registers */

 	u32		irq;

 	u32		speed_hz; /* SCK has a fixed frequency of speed_hz Hz */

 	u8 *rx_ptr;		/* pointer in the Tx buffer */
 	const u8 *tx_ptr;	/* pointer in the Rx buffer */
 	int remaining_bytes;	/* the number of bytes left to transfer */
 };

 static void xspi_init_hw(void __iomem *regs_base)
 {
 	/* Reset the SPI device */
 	out_be32(regs_base + XIPIF_V123B_RESETR_OFFSET,
 		 XIPIF_V123B_RESET_MASK);
 	/* Disable all the interrupts just in case */
 	out_be32(regs_base + XIPIF_V123B_IIER_OFFSET, 0);
 	/* Enable the global IPIF interrupt */
 	out_be32(regs_base + XIPIF_V123B_DGIER_OFFSET,
 		 XIPIF_V123B_GINTR_ENABLE);
 	/* Deselect the slave on the SPI bus */
 	out_be32(regs_base + XSPI_SSR_OFFSET, 0xffff);
 	/* Disable the transmitter, enable Manual Slave Select Assertion,
 	 * put SPI controller into master mode, and enable it */
 	out_be16(regs_base + XSPI_CR_OFFSET,
 		 XSPI_CR_TRANS_INHIBIT | XSPI_CR_MANUAL_SSELECT
 		 | XSPI_CR_MASTER_MODE | XSPI_CR_ENABLE);
 }

 static void xilinx_spi_chipselect(struct spi_device *spi, int is_on)
 {
 	struct xilinx_spi *xspi = spi_master_get_devdata(spi->master);

 	if (is_on == BITBANG_CS_INACTIVE) {
 		/* Deselect the slave on the SPI bus */
 		out_be32(xspi->regs + XSPI_SSR_OFFSET, 0xffff);
 	} else if (is_on == BITBANG_CS_ACTIVE) {
 		/* Set the SPI clock phase and polarity */
 		u16 cr = in_be16(xspi->regs + XSPI_CR_OFFSET)
 			 & ~XSPI_CR_MODE_MASK;
 		if (spi->mode & SPI_CPHA)
 			cr |= XSPI_CR_CPHA;
 		if (spi->mode & SPI_CPOL)
 			cr |= XSPI_CR_CPOL;
 		out_be16(xspi->regs + XSPI_CR_OFFSET, cr);

 		/* We do not check spi->max_speed_hz here as the SPI clock
 		 * frequency is not software programmable (the IP block design
 		 * parameter)
 		 */

 		/* Activate the chip select */
 		out_be32(xspi->regs + XSPI_SSR_OFFSET,
 			 ~(0x0001 << spi->chip_select));
 	}
 }

 /* spi_bitbang requires custom setup_transfer() to be defined if there is a
  * custom txrx_bufs(). We have nothing to setup here as the SPI IP block
  * supports just 8 bits per word, and SPI clock can't be changed in software.
  * Check for 8 bits per word. Chip select delay calculations could be
  * added here as soon as bitbang_work() can be made aware of the delay value.
  */
 static int xilinx_spi_setup_transfer(struct spi_device *spi,
 		struct spi_transfer *t)
 {
 	u8 bits_per_word;

 	bits_per_word = (t && t->bits_per_word)
 			 ? t->bits_per_word : spi->bits_per_word;
 	if (bits_per_word != 8) {
 		dev_err(&spi->dev, "%s, unsupported bits_per_word=%d\n",
 			__func__, bits_per_word);
 		return -EINVAL;
 	}

 	return 0;
 }

 static int xilinx_spi_setup(struct spi_device *spi)
 {
 	struct spi_bitbang *bitbang;
 	struct xilinx_spi *xspi;
 	int retval;

 	xspi = spi_master_get_devdata(spi->master);
 	bitbang = &xspi->bitbang;

 	retval = xilinx_spi_setup_transfer(spi, NULL);
 	if (retval < 0)
 		return retval;

 	return 0;
 }

 static void xilinx_spi_fill_tx_fifo(struct xilinx_spi *xspi)
 {
 	u8 sr;

 	/* Fill the Tx FIFO with as many bytes as possible */
 	sr = in_8(xspi->regs + XSPI_SR_OFFSET);
 	while ((sr & XSPI_SR_TX_FULL_MASK) == 0 && xspi->remaining_bytes > 0) {
 		if (xspi->tx_ptr) {
 			out_8(xspi->regs + XSPI_TXD_OFFSET, *xspi->tx_ptr++);
 		} else {
 			out_8(xspi->regs + XSPI_TXD_OFFSET, 0);
 		}
 		xspi->remaining_bytes--;
 		sr = in_8(xspi->regs + XSPI_SR_OFFSET);
 	}
 }

 static int xilinx_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
 {
 	struct xilinx_spi *xspi = spi_master_get_devdata(spi->master);
 	u32 ipif_ier;
 	u16 cr;

 	/* We get here with transmitter inhibited */

 	xspi->tx_ptr = t->tx_buf;
 	xspi->rx_ptr = t->rx_buf;
 	xspi->remaining_bytes = t->len;
 	INIT_COMPLETION(xspi->done);

 	xilinx_spi_fill_tx_fifo(xspi);

 	/* Enable the transmit empty interrupt, which we use to determine
 	 * progress on the transmission.
 	 */
 	ipif_ier = in_be32(xspi->regs + XIPIF_V123B_IIER_OFFSET);
 	out_be32(xspi->regs + XIPIF_V123B_IIER_OFFSET,
 		 ipif_ier | XSPI_INTR_TX_EMPTY);

 	/* Start the transfer by not inhibiting the transmitter any longer */
 	cr = in_be16(xspi->regs + XSPI_CR_OFFSET) & ~XSPI_CR_TRANS_INHIBIT;
 	out_be16(xspi->regs + XSPI_CR_OFFSET, cr);

 	wait_for_completion(&xspi->done);

 	/* Disable the transmit empty interrupt */
 	out_be32(xspi->regs + XIPIF_V123B_IIER_OFFSET, ipif_ier);

 	return t->len - xspi->remaining_bytes;
 }


 /* This driver supports single master mode only. Hence Tx FIFO Empty
  * is the only interrupt we care about.
  * Receive FIFO Overrun, Transmit FIFO Underrun, Mode Fault, and Slave Mode
  * Fault are not to happen.
  */
 static irqreturn_t xilinx_spi_irq(int irq, void *dev_id)
 {
 	struct xilinx_spi *xspi = dev_id;
 	u32 ipif_isr;

 	/* Get the IPIF interrupts, and clear them immediately */
 	ipif_isr = in_be32(xspi->regs + XIPIF_V123B_IISR_OFFSET);
 	out_be32(xspi->regs + XIPIF_V123B_IISR_OFFSET, ipif_isr);

 	if (ipif_isr & XSPI_INTR_TX_EMPTY) {	/* Transmission completed */
 		u16 cr;
 		u8 sr;

 		/* A transmit has just completed. Process received data and
 		 * check for more data to transmit. Always inhibit the
 		 * transmitter while the Isr refills the transmit register/FIFO,
 		 * or make sure it is stopped if we're done.
 		 */
 		cr = in_be16(xspi->regs + XSPI_CR_OFFSET);
 		out_be16(xspi->regs + XSPI_CR_OFFSET,
 			 cr | XSPI_CR_TRANS_INHIBIT);

 		/* Read out all the data from the Rx FIFO */
 		sr = in_8(xspi->regs + XSPI_SR_OFFSET);
 		while ((sr & XSPI_SR_RX_EMPTY_MASK) == 0) {
 			u8 data;

 			data = in_8(xspi->regs + XSPI_RXD_OFFSET);
 			if (xspi->rx_ptr) {
 				*xspi->rx_ptr++ = data;
 			}
 			sr = in_8(xspi->regs + XSPI_SR_OFFSET);
 		}

 		/* See if there is more data to send */
 		if (xspi->remaining_bytes > 0) {
 			xilinx_spi_fill_tx_fifo(xspi);
 			/* Start the transfer by not inhibiting the
 			 * transmitter any longer
 			 */
 			out_be16(xspi->regs + XSPI_CR_OFFSET, cr);
 		} else {
 			/* No more data to send.
 			 * Indicate the transfer is completed.
 			 */
 			complete(&xspi->done);
 		}
 	}

 	return IRQ_HANDLED;
 }

 static int __init xilinx_spi_of_probe(struct of_device *ofdev,
 					const struct of_device_id *match)
 {
 	struct spi_master *master;
 	struct xilinx_spi *xspi;
 	struct resource r_irq_struct;
 	struct resource r_mem_struct;

 	struct resource *r_irq = &r_irq_struct;
 	struct resource *r_mem = &r_mem_struct;
 	int rc = 0;
 	const u32 *prop;
 	int len;

 	/* Get resources(memory, IRQ) associated with the device */
 	master = spi_alloc_master(&ofdev->dev, sizeof(struct xilinx_spi));

 	if (master == NULL) {
 		return -ENOMEM;
 	}

 	dev_set_drvdata(&ofdev->dev, master);

 	rc = of_address_to_resource(ofdev->node, 0, r_mem);
 	if (rc) {
 		dev_warn(&ofdev->dev, "invalid address\n");
 		goto put_master;
 	}

 	rc = of_irq_to_resource(ofdev->node, 0, r_irq);
 	if (rc == NO_IRQ) {
 		dev_warn(&ofdev->dev, "no IRQ found\n");
 		goto put_master;
 	}

 	/* the spi->mode bits understood by this driver: */
 	master->mode_bits = SPI_CPOL | SPI_CPHA;

 	xspi = spi_master_get_devdata(master);
 	xspi->bitbang.master = spi_master_get(master);
 	xspi->bitbang.chipselect = xilinx_spi_chipselect;
 	xspi->bitbang.setup_transfer = xilinx_spi_setup_transfer;
 	xspi->bitbang.txrx_bufs = xilinx_spi_txrx_bufs;
 	xspi->bitbang.master->setup = xilinx_spi_setup;
 	init_completion(&xspi->done);

 	xspi->irq = r_irq->start;

 	if (!request_mem_region(r_mem->start,
 			r_mem->end - r_mem->start + 1, XILINX_SPI_NAME)) {
 		rc = -ENXIO;
 		dev_warn(&ofdev->dev, "memory request failure\n");
 		goto put_master;
 	}

 	xspi->regs = ioremap(r_mem->start, r_mem->end - r_mem->start + 1);
 	if (xspi->regs == NULL) {
 		rc = -ENOMEM;
 		dev_warn(&ofdev->dev, "ioremap failure\n");
 		goto release_mem;
 	}
 	xspi->irq = r_irq->start;

 	/* dynamic bus assignment */
 	master->bus_num = -1;

 	/* number of slave select bits is required */
 	prop = of_get_property(ofdev->node, "xlnx,num-ss-bits", &len);
 	if (!prop || len < sizeof(*prop)) {
 		dev_warn(&ofdev->dev, "no 'xlnx,num-ss-bits' property\n");
 		goto unmap_io;
 	}
 	master->num_chipselect = *prop;

 	/* SPI controller initializations */
 	xspi_init_hw(xspi->regs);

 	/* Register for SPI Interrupt */
 	rc = request_irq(xspi->irq, xilinx_spi_irq, 0, XILINX_SPI_NAME, xspi);
 	if (rc != 0) {
 		dev_warn(&ofdev->dev, "irq request failure: %d\n", xspi->irq);
 		goto unmap_io;
 	}

 	rc = spi_bitbang_start(&xspi->bitbang);
 	if (rc != 0) {
 		dev_err(&ofdev->dev, "spi_bitbang_start FAILED\n");
 		goto free_irq;
 	}

 	dev_info(&ofdev->dev, "at 0x%08X mapped to 0x%08X, irq=%d\n",
 			(unsigned int)r_mem->start, (u32)xspi->regs, xspi->irq);

 	/* Add any subnodes on the SPI bus */
 	of_register_spi_devices(master, ofdev->node);

 	return rc;

 free_irq:
 	free_irq(xspi->irq, xspi);
 unmap_io:
 	iounmap(xspi->regs);
 release_mem:
 	release_mem_region(r_mem->start, resource_size(r_mem));
 put_master:
 	spi_master_put(master);
 	return rc;
 }

 static int __devexit xilinx_spi_remove(struct of_device *ofdev)
 {
 	struct xilinx_spi *xspi;
 	struct spi_master *master;
 	struct resource r_mem;

 	master = platform_get_drvdata(ofdev);
 	xspi = spi_master_get_devdata(master);

 	spi_bitbang_stop(&xspi->bitbang);
 	free_irq(xspi->irq, xspi);
 	iounmap(xspi->regs);
 	if (!of_address_to_resource(ofdev->node, 0, &r_mem))
 		release_mem_region(r_mem.start, resource_size(&r_mem));
 	dev_set_drvdata(&ofdev->dev, 0);
 	spi_master_put(xspi->bitbang.master);

 	return 0;
 }

 /* work with hotplug and coldplug */
 MODULE_ALIAS("platform:" XILINX_SPI_NAME);

 static int __exit xilinx_spi_of_remove(struct of_device *op)
 {
 	return xilinx_spi_remove(op);
 }

 static struct of_device_id xilinx_spi_of_match[] = {
 	{ .compatible = "xlnx,xps-spi-2.00.a", },
 	{ .compatible = "xlnx,xps-spi-2.00.b", },
 	{}
 };

 MODULE_DEVICE_TABLE(of, xilinx_spi_of_match);

 static struct of_platform_driver xilinx_spi_of_driver = {
 	.owner = THIS_MODULE,
 	.name = "xilinx-xps-spi",
 	.match_table = xilinx_spi_of_match,
 	.probe = xilinx_spi_of_probe,
 	.remove = __exit_p(xilinx_spi_of_remove),
 	.driver = {
 		.name = "xilinx-xps-spi",
 		.owner = THIS_MODULE,
 	},
 };

 static int __init xilinx_spi_init(void)
 {
 	return of_register_platform_driver(&xilinx_spi_of_driver);
 }
 module_init(xilinx_spi_init);

 static void __exit xilinx_spi_exit(void)
 {
 	of_unregister_platform_driver(&xilinx_spi_of_driver);
 }
 module_exit(xilinx_spi_exit);
 MODULE_AUTHOR("MontaVista Software, Inc. <source@mvista.com>");
 MODULE_DESCRIPTION("Xilinx SPI driver");
 MODULE_LICENSE("GPL");
	/*
	* xilinx_spi.c
	*
	* Xilinx SPI controller driver (master mode only)
	*
	* Author: MontaVista Software, Inc.
	* source@mvista.com
	*
	* 2002-2007 (c) MontaVista Software, Inc. This file is licensed under the
	* terms of the GNU General Public License version 2. This program is licensed
	* "as is" without any warranty of any kind, whether express or implied.
	*/

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/interrupt.h>
	#include <linux/platform_device.h>

	#include <linux/of_platform.h>
	#include <linux/of_device.h>
	#include <linux/of_spi.h>

	#include <linux/spi/spi.h>
	#include <linux/spi/spi_bitbang.h>
	#include <linux/io.h>

	#define XILINX_SPI_NAME "xilinx_spi"

	/* Register definitions as per "OPB Serial Peripheral Interface (SPI) (v1.00e)
	* Product Specification", DS464
	*/
	#define XSPI_CR_OFFSET 0x62 /* 16-bit Control Register */

	#define XSPI_CR_ENABLE 0x02
	#define XSPI_CR_MASTER_MODE 0x04
	#define XSPI_CR_CPOL 0x08
	#define XSPI_CR_CPHA 0x10
	#define XSPI_CR_MODE_MASK (XSPI_CR_CPHA \| XSPI_CR_CPOL)
	#define XSPI_CR_TXFIFO_RESET 0x20
	#define XSPI_CR_RXFIFO_RESET 0x40
	#define XSPI_CR_MANUAL_SSELECT 0x80
	#define XSPI_CR_TRANS_INHIBIT 0x100

	#define XSPI_SR_OFFSET 0x67 /* 8-bit Status Register */

	#define XSPI_SR_RX_EMPTY_MASK 0x01 /* Receive FIFO is empty */
	#define XSPI_SR_RX_FULL_MASK 0x02 /* Receive FIFO is full */
	#define XSPI_SR_TX_EMPTY_MASK 0x04 /* Transmit FIFO is empty */
	#define XSPI_SR_TX_FULL_MASK 0x08 /* Transmit FIFO is full */
	#define XSPI_SR_MODE_FAULT_MASK 0x10 /* Mode fault error */

	#define XSPI_TXD_OFFSET 0x6b /* 8-bit Data Transmit Register */
	#define XSPI_RXD_OFFSET 0x6f /* 8-bit Data Receive Register */

	#define XSPI_SSR_OFFSET 0x70 /* 32-bit Slave Select Register */

	/* Register definitions as per "OPB IPIF (v3.01c) Product Specification", DS414
	* IPIF registers are 32 bit
	*/
	#define XIPIF_V123B_DGIER_OFFSET 0x1c /* IPIF global int enable reg */
	#define XIPIF_V123B_GINTR_ENABLE 0x80000000

	#define XIPIF_V123B_IISR_OFFSET 0x20 /* IPIF interrupt status reg */
	#define XIPIF_V123B_IIER_OFFSET 0x28 /* IPIF interrupt enable reg */

	#define XSPI_INTR_MODE_FAULT 0x01 /* Mode fault error */
	#define XSPI_INTR_SLAVE_MODE_FAULT 0x02 /* Selected as slave while
	* disabled */
	#define XSPI_INTR_TX_EMPTY 0x04 /* TxFIFO is empty */
	#define XSPI_INTR_TX_UNDERRUN 0x08 /* TxFIFO was underrun */
	#define XSPI_INTR_RX_FULL 0x10 /* RxFIFO is full */
	#define XSPI_INTR_RX_OVERRUN 0x20 /* RxFIFO was overrun */

	#define XIPIF_V123B_RESETR_OFFSET 0x40 /* IPIF reset register */
	#define XIPIF_V123B_RESET_MASK 0x0a /* the value to write */

	struct xilinx_spi {
	/* bitbang has to be first */
	struct spi_bitbang bitbang;
	struct completion done;

	void __iomem regs; / virt. address of the control registers */

	u32 irq;

	u32 speed_hz; /* SCK has a fixed frequency of speed_hz Hz */

	u8 rx_ptr; / pointer in the Tx buffer */
	const u8 tx_ptr; / pointer in the Rx buffer */
	int remaining_bytes; /* the number of bytes left to transfer */
	};

	static void xspi_init_hw(void __iomem *regs_base)
	{
	/* Reset the SPI device */
	out_be32(regs_base + XIPIF_V123B_RESETR_OFFSET,
	XIPIF_V123B_RESET_MASK);
	/* Disable all the interrupts just in case */
	out_be32(regs_base + XIPIF_V123B_IIER_OFFSET, 0);
	/* Enable the global IPIF interrupt */
	out_be32(regs_base + XIPIF_V123B_DGIER_OFFSET,
	XIPIF_V123B_GINTR_ENABLE);
	/* Deselect the slave on the SPI bus */
	out_be32(regs_base + XSPI_SSR_OFFSET, 0xffff);
	/* Disable the transmitter, enable Manual Slave Select Assertion,
	* put SPI controller into master mode, and enable it */
	out_be16(regs_base + XSPI_CR_OFFSET,
	XSPI_CR_TRANS_INHIBIT \| XSPI_CR_MANUAL_SSELECT
	\| XSPI_CR_MASTER_MODE \| XSPI_CR_ENABLE);
	}

	static void xilinx_spi_chipselect(struct spi_device *spi, int is_on)
	{
	struct xilinx_spi *xspi = spi_master_get_devdata(spi->master);

	if (is_on == BITBANG_CS_INACTIVE) {
	/* Deselect the slave on the SPI bus */
	out_be32(xspi->regs + XSPI_SSR_OFFSET, 0xffff);
	} else if (is_on == BITBANG_CS_ACTIVE) {
	/* Set the SPI clock phase and polarity */
	u16 cr = in_be16(xspi->regs + XSPI_CR_OFFSET)
	& ~XSPI_CR_MODE_MASK;
	if (spi->mode & SPI_CPHA)
	cr \|= XSPI_CR_CPHA;
	if (spi->mode & SPI_CPOL)
	cr \|= XSPI_CR_CPOL;
	out_be16(xspi->regs + XSPI_CR_OFFSET, cr);

	/* We do not check spi->max_speed_hz here as the SPI clock
	* frequency is not software programmable (the IP block design
	* parameter)
	*/

	/* Activate the chip select */
	out_be32(xspi->regs + XSPI_SSR_OFFSET,
	~(0x0001 << spi->chip_select));
	}
	}

	/* spi_bitbang requires custom setup_transfer() to be defined if there is a
	* custom txrx_bufs(). We have nothing to setup here as the SPI IP block
	* supports just 8 bits per word, and SPI clock can't be changed in software.
	* Check for 8 bits per word. Chip select delay calculations could be
	* added here as soon as bitbang_work() can be made aware of the delay value.
	*/
	static int xilinx_spi_setup_transfer(struct spi_device *spi,
	struct spi_transfer *t)
	{
	u8 bits_per_word;

	bits_per_word = (t && t->bits_per_word)
	? t->bits_per_word : spi->bits_per_word;
	if (bits_per_word != 8) {
	dev_err(&spi->dev, "%s, unsupported bits_per_word=%d\n",
	__func__, bits_per_word);
	return -EINVAL;
	}

	return 0;
	}

	static int xilinx_spi_setup(struct spi_device *spi)
	{
	struct spi_bitbang *bitbang;
	struct xilinx_spi *xspi;
	int retval;

	xspi = spi_master_get_devdata(spi->master);
	bitbang = &xspi->bitbang;

	retval = xilinx_spi_setup_transfer(spi, NULL);
	if (retval < 0)
	return retval;

	return 0;
	}

	static void xilinx_spi_fill_tx_fifo(struct xilinx_spi *xspi)
	{
	u8 sr;

	/* Fill the Tx FIFO with as many bytes as possible */
	sr = in_8(xspi->regs + XSPI_SR_OFFSET);
	while ((sr & XSPI_SR_TX_FULL_MASK) == 0 && xspi->remaining_bytes > 0) {
	if (xspi->tx_ptr) {
	out_8(xspi->regs + XSPI_TXD_OFFSET, *xspi->tx_ptr++);
	} else {
	out_8(xspi->regs + XSPI_TXD_OFFSET, 0);
	}
	xspi->remaining_bytes--;
	sr = in_8(xspi->regs + XSPI_SR_OFFSET);
	}
	}

	static int xilinx_spi_txrx_bufs(struct spi_device spi, struct spi_transfer t)
	{
	struct xilinx_spi *xspi = spi_master_get_devdata(spi->master);
	u32 ipif_ier;
	u16 cr;

	/* We get here with transmitter inhibited */

	xspi->tx_ptr = t->tx_buf;
	xspi->rx_ptr = t->rx_buf;
	xspi->remaining_bytes = t->len;
	INIT_COMPLETION(xspi->done);

	xilinx_spi_fill_tx_fifo(xspi);

	/* Enable the transmit empty interrupt, which we use to determine
	* progress on the transmission.
	*/
	ipif_ier = in_be32(xspi->regs + XIPIF_V123B_IIER_OFFSET);
	out_be32(xspi->regs + XIPIF_V123B_IIER_OFFSET,
	ipif_ier \| XSPI_INTR_TX_EMPTY);

	/* Start the transfer by not inhibiting the transmitter any longer */
	cr = in_be16(xspi->regs + XSPI_CR_OFFSET) & ~XSPI_CR_TRANS_INHIBIT;
	out_be16(xspi->regs + XSPI_CR_OFFSET, cr);

	wait_for_completion(&xspi->done);

	/* Disable the transmit empty interrupt */
	out_be32(xspi->regs + XIPIF_V123B_IIER_OFFSET, ipif_ier);

	return t->len - xspi->remaining_bytes;
	}


	/* This driver supports single master mode only. Hence Tx FIFO Empty
	* is the only interrupt we care about.
	* Receive FIFO Overrun, Transmit FIFO Underrun, Mode Fault, and Slave Mode
	* Fault are not to happen.
	*/
	static irqreturn_t xilinx_spi_irq(int irq, void *dev_id)
	{
	struct xilinx_spi *xspi = dev_id;
	u32 ipif_isr;

	/* Get the IPIF interrupts, and clear them immediately */
	ipif_isr = in_be32(xspi->regs + XIPIF_V123B_IISR_OFFSET);
	out_be32(xspi->regs + XIPIF_V123B_IISR_OFFSET, ipif_isr);

	if (ipif_isr & XSPI_INTR_TX_EMPTY) { /* Transmission completed */
	u16 cr;
	u8 sr;

	/* A transmit has just completed. Process received data and
	* check for more data to transmit. Always inhibit the
	* transmitter while the Isr refills the transmit register/FIFO,
	* or make sure it is stopped if we're done.
	*/
	cr = in_be16(xspi->regs + XSPI_CR_OFFSET);
	out_be16(xspi->regs + XSPI_CR_OFFSET,
	cr \| XSPI_CR_TRANS_INHIBIT);

	/* Read out all the data from the Rx FIFO */
	sr = in_8(xspi->regs + XSPI_SR_OFFSET);
	while ((sr & XSPI_SR_RX_EMPTY_MASK) == 0) {
	u8 data;

	data = in_8(xspi->regs + XSPI_RXD_OFFSET);
	if (xspi->rx_ptr) {
	*xspi->rx_ptr++ = data;
	}
	sr = in_8(xspi->regs + XSPI_SR_OFFSET);
	}

	/* See if there is more data to send */
	if (xspi->remaining_bytes > 0) {
	xilinx_spi_fill_tx_fifo(xspi);
	/* Start the transfer by not inhibiting the
	* transmitter any longer
	*/
	out_be16(xspi->regs + XSPI_CR_OFFSET, cr);
	} else {
	/* No more data to send.
	* Indicate the transfer is completed.
	*/
	complete(&xspi->done);
	}
	}

	return IRQ_HANDLED;
	}

	static int __init xilinx_spi_of_probe(struct of_device *ofdev,
	const struct of_device_id *match)
	{
	struct spi_master *master;
	struct xilinx_spi *xspi;
	struct resource r_irq_struct;
	struct resource r_mem_struct;

	struct resource *r_irq = &r_irq_struct;
	struct resource *r_mem = &r_mem_struct;
	int rc = 0;
	const u32 *prop;
	int len;

	/* Get resources(memory, IRQ) associated with the device */
	master = spi_alloc_master(&ofdev->dev, sizeof(struct xilinx_spi));

	if (master == NULL) {
	return -ENOMEM;
	}

	dev_set_drvdata(&ofdev->dev, master);

	rc = of_address_to_resource(ofdev->node, 0, r_mem);
	if (rc) {
	dev_warn(&ofdev->dev, "invalid address\n");
	goto put_master;
	}

	rc = of_irq_to_resource(ofdev->node, 0, r_irq);
	if (rc == NO_IRQ) {
	dev_warn(&ofdev->dev, "no IRQ found\n");
	goto put_master;
	}

	/* the spi->mode bits understood by this driver: */
	master->mode_bits = SPI_CPOL \| SPI_CPHA;

	xspi = spi_master_get_devdata(master);
	xspi->bitbang.master = spi_master_get(master);
	xspi->bitbang.chipselect = xilinx_spi_chipselect;
	xspi->bitbang.setup_transfer = xilinx_spi_setup_transfer;
	xspi->bitbang.txrx_bufs = xilinx_spi_txrx_bufs;
	xspi->bitbang.master->setup = xilinx_spi_setup;
	init_completion(&xspi->done);

	xspi->irq = r_irq->start;

	if (!request_mem_region(r_mem->start,
	r_mem->end - r_mem->start + 1, XILINX_SPI_NAME)) {
	rc = -ENXIO;
	dev_warn(&ofdev->dev, "memory request failure\n");
	goto put_master;
	}

	xspi->regs = ioremap(r_mem->start, r_mem->end - r_mem->start + 1);
	if (xspi->regs == NULL) {
	rc = -ENOMEM;
	dev_warn(&ofdev->dev, "ioremap failure\n");
	goto release_mem;
	}
	xspi->irq = r_irq->start;

	/* dynamic bus assignment */
	master->bus_num = -1;

	/* number of slave select bits is required */
	prop = of_get_property(ofdev->node, "xlnx,num-ss-bits", &len);
	if (!prop \|\| len < sizeof(*prop)) {
	dev_warn(&ofdev->dev, "no 'xlnx,num-ss-bits' property\n");
	goto unmap_io;
	}
	master->num_chipselect = *prop;

	/* SPI controller initializations */
	xspi_init_hw(xspi->regs);

	/* Register for SPI Interrupt */
	rc = request_irq(xspi->irq, xilinx_spi_irq, 0, XILINX_SPI_NAME, xspi);
	if (rc != 0) {
	dev_warn(&ofdev->dev, "irq request failure: %d\n", xspi->irq);
	goto unmap_io;
	}

	rc = spi_bitbang_start(&xspi->bitbang);
	if (rc != 0) {
	dev_err(&ofdev->dev, "spi_bitbang_start FAILED\n");
	goto free_irq;
	}

	dev_info(&ofdev->dev, "at 0x%08X mapped to 0x%08X, irq=%d\n",
	(unsigned int)r_mem->start, (u32)xspi->regs, xspi->irq);

	/* Add any subnodes on the SPI bus */
	of_register_spi_devices(master, ofdev->node);

	return rc;

	free_irq:
	free_irq(xspi->irq, xspi);
	unmap_io:
	iounmap(xspi->regs);
	release_mem:
	release_mem_region(r_mem->start, resource_size(r_mem));
	put_master:
	spi_master_put(master);
	return rc;
	}

	static int __devexit xilinx_spi_remove(struct of_device *ofdev)
	{
	struct xilinx_spi *xspi;
	struct spi_master *master;
	struct resource r_mem;

	master = platform_get_drvdata(ofdev);
	xspi = spi_master_get_devdata(master);

	spi_bitbang_stop(&xspi->bitbang);
	free_irq(xspi->irq, xspi);
	iounmap(xspi->regs);
	if (!of_address_to_resource(ofdev->node, 0, &r_mem))
	release_mem_region(r_mem.start, resource_size(&r_mem));
	dev_set_drvdata(&ofdev->dev, 0);
	spi_master_put(xspi->bitbang.master);

	return 0;
	}

	/* work with hotplug and coldplug */
	MODULE_ALIAS("platform:" XILINX_SPI_NAME);

	static int __exit xilinx_spi_of_remove(struct of_device *op)
	{
	return xilinx_spi_remove(op);
	}

	static struct of_device_id xilinx_spi_of_match[] = {
	{ .compatible = "xlnx,xps-spi-2.00.a", },
	{ .compatible = "xlnx,xps-spi-2.00.b", },
	{}
	};

	MODULE_DEVICE_TABLE(of, xilinx_spi_of_match);

	static struct of_platform_driver xilinx_spi_of_driver = {
	.owner = THIS_MODULE,
	.name = "xilinx-xps-spi",
	.match_table = xilinx_spi_of_match,
	.probe = xilinx_spi_of_probe,
	.remove = __exit_p(xilinx_spi_of_remove),
	.driver = {
	.name = "xilinx-xps-spi",
	.owner = THIS_MODULE,
	},
	};

	static int __init xilinx_spi_init(void)
	{
	return of_register_platform_driver(&xilinx_spi_of_driver);
	}
	module_init(xilinx_spi_init);

	static void __exit xilinx_spi_exit(void)
	{
	of_unregister_platform_driver(&xilinx_spi_of_driver);
	}
	module_exit(xilinx_spi_exit);
	MODULE_AUTHOR("MontaVista Software, Inc. <source@mvista.com>");
	MODULE_DESCRIPTION("Xilinx SPI driver");
	MODULE_LICENSE("GPL");