drivers/spi/ep93xx_spi.c



011f23a3c2f


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/*
 * Driver for Cirrus Logic EP93xx SPI controller.
 *
 * Copyright (c) 2010 Mika Westerberg
 *
 * Explicit FIFO handling code was inspired by amba-pl022 driver.
 *
 * Chip select support using other than built-in GPIOs by H. Hartley Sweeten.
 *
 * For more information about the SPI controller see documentation on Cirrus
 * Logic web site:
 *     http://www.cirrus.com/en/pubs/manual/EP93xx_Users_Guide_UM1.pdf
 *
 * 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.
 */

#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/bitops.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/workqueue.h>
#include <linux/sched.h>
#include <linux/spi/spi.h>

#include <mach/ep93xx_spi.h>

#define SSPCR0			0x0000
#define SSPCR0_MODE_SHIFT	6
#define SSPCR0_SCR_SHIFT	8

#define SSPCR1			0x0004
#define SSPCR1_RIE		BIT(0)
#define SSPCR1_TIE		BIT(1)
#define SSPCR1_RORIE		BIT(2)
#define SSPCR1_LBM		BIT(3)
#define SSPCR1_SSE		BIT(4)
#define SSPCR1_MS		BIT(5)
#define SSPCR1_SOD		BIT(6)

#define SSPDR			0x0008

#define SSPSR			0x000c
#define SSPSR_TFE		BIT(0)
#define SSPSR_TNF		BIT(1)
#define SSPSR_RNE		BIT(2)
#define SSPSR_RFF		BIT(3)
#define SSPSR_BSY		BIT(4)
#define SSPCPSR			0x0010

#define SSPIIR			0x0014
#define SSPIIR_RIS		BIT(0)
#define SSPIIR_TIS		BIT(1)
#define SSPIIR_RORIS		BIT(2)
#define SSPICR			SSPIIR

/* timeout in milliseconds */
#define SPI_TIMEOUT		5
/* maximum depth of RX/TX FIFO */
#define SPI_FIFO_SIZE		8

/**
 * struct ep93xx_spi - EP93xx SPI controller structure
 * @lock: spinlock that protects concurrent accesses to fields @running,
 *        @current_msg and @msg_queue
 * @pdev: pointer to platform device
 * @clk: clock for the controller
 * @regs_base: pointer to ioremap()'d registers
 * @irq: IRQ number used by the driver
 * @min_rate: minimum clock rate (in Hz) supported by the controller
 * @max_rate: maximum clock rate (in Hz) supported by the controller
 * @running: is the queue running
 * @wq: workqueue used by the driver
 * @msg_work: work that is queued for the driver
 * @wait: wait here until given transfer is completed
 * @msg_queue: queue for the messages
 * @current_msg: message that is currently processed (or %NULL if none)
 * @tx: current byte in transfer to transmit
 * @rx: current byte in transfer to receive
 * @fifo_level: how full is FIFO (%0..%SPI_FIFO_SIZE - %1). Receiving one
 *              frame decreases this level and sending one frame increases it.
 *
 * This structure holds EP93xx SPI controller specific information. When
 * @running is %true, driver accepts transfer requests from protocol drivers.
 * @current_msg is used to hold pointer to the message that is currently
 * processed. If @current_msg is %NULL, it means that no processing is going
 * on.
 *
 * Most of the fields are only written once and they can be accessed without
 * taking the @lock. Fields that are accessed concurrently are: @current_msg,
 * @running, and @msg_queue.
 */
struct ep93xx_spi {
	spinlock_t			lock;
	const struct platform_device	*pdev;
	struct clk			*clk;
	void __iomem			*regs_base;
	int				irq;
	unsigned long			min_rate;
	unsigned long			max_rate;
	bool				running;
	struct workqueue_struct		*wq;
	struct work_struct		msg_work;
	struct completion		wait;
	struct list_head		msg_queue;
	struct spi_message		*current_msg;
	size_t				tx;
	size_t				rx;
	size_t				fifo_level;
};

/**
 * struct ep93xx_spi_chip - SPI device hardware settings
 * @spi: back pointer to the SPI device
 * @rate: max rate in hz this chip supports
 * @div_cpsr: cpsr (pre-scaler) divider
 * @div_scr: scr divider
 * @dss: bits per word (4 - 16 bits)
 * @ops: private chip operations
 *
 * This structure is used to store hardware register specific settings for each
 * SPI device. Settings are written to hardware by function
 * ep93xx_spi_chip_setup().
 */
struct ep93xx_spi_chip {
	const struct spi_device		*spi;
	unsigned long			rate;
	u8				div_cpsr;
	u8				div_scr;
	u8				dss;
	struct ep93xx_spi_chip_ops	*ops;
};

/* converts bits per word to CR0.DSS value */
#define bits_per_word_to_dss(bpw)	((bpw) - 1)

static inline void
ep93xx_spi_write_u8(const struct ep93xx_spi *espi, u16 reg, u8 value)
{
	__raw_writeb(value, espi->regs_base + reg);
}

static inline u8
ep93xx_spi_read_u8(const struct ep93xx_spi *spi, u16 reg)
{
	return __raw_readb(spi->regs_base + reg);
}

static inline void
ep93xx_spi_write_u16(const struct ep93xx_spi *espi, u16 reg, u16 value)
{
	__raw_writew(value, espi->regs_base + reg);
}

static inline u16
ep93xx_spi_read_u16(const struct ep93xx_spi *spi, u16 reg)
{
	return __raw_readw(spi->regs_base + reg);
}

static int ep93xx_spi_enable(const struct ep93xx_spi *espi)
{
	u8 regval;
	int err;

	err = clk_enable(espi->clk);
	if (err)
		return err;

	regval = ep93xx_spi_read_u8(espi, SSPCR1);
	regval |= SSPCR1_SSE;
	ep93xx_spi_write_u8(espi, SSPCR1, regval);

	return 0;
}

static void ep93xx_spi_disable(const struct ep93xx_spi *espi)
{
	u8 regval;

	regval = ep93xx_spi_read_u8(espi, SSPCR1);
	regval &= ~SSPCR1_SSE;
	ep93xx_spi_write_u8(espi, SSPCR1, regval);

	clk_disable(espi->clk);
}

static void ep93xx_spi_enable_interrupts(const struct ep93xx_spi *espi)
{
	u8 regval;

	regval = ep93xx_spi_read_u8(espi, SSPCR1);
	regval |= (SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
	ep93xx_spi_write_u8(espi, SSPCR1, regval);
}

static void ep93xx_spi_disable_interrupts(const struct ep93xx_spi *espi)
{
	u8 regval;

	regval = ep93xx_spi_read_u8(espi, SSPCR1);
	regval &= ~(SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
	ep93xx_spi_write_u8(espi, SSPCR1, regval);
}

/**
 * ep93xx_spi_calc_divisors() - calculates SPI clock divisors
 * @espi: ep93xx SPI controller struct
 * @chip: divisors are calculated for this chip
 * @rate: desired SPI output clock rate
 *
 * Function calculates cpsr (clock pre-scaler) and scr divisors based on
 * given @rate and places them to @chip->div_cpsr and @chip->div_scr. If,
 * for some reason, divisors cannot be calculated nothing is stored and
 * %-EINVAL is returned.
 */
static int ep93xx_spi_calc_divisors(const struct ep93xx_spi *espi,
				    struct ep93xx_spi_chip *chip,
				    unsigned long rate)
{
	unsigned long spi_clk_rate = clk_get_rate(espi->clk);
	int cpsr, scr;

	/*
	 * Make sure that max value is between values supported by the
	 * controller. Note that minimum value is already checked in
	 * ep93xx_spi_transfer().
	 */
	rate = clamp(rate, espi->min_rate, espi->max_rate);

	/*
	 * Calculate divisors so that we can get speed according the
	 * following formula:
	 *	rate = spi_clock_rate / (cpsr * (1 + scr))
	 *
	 * cpsr must be even number and starts from 2, scr can be any number
	 * between 0 and 255.
	 */
	for (cpsr = 2; cpsr <= 254; cpsr += 2) {
		for (scr = 0; scr <= 255; scr++) {
			if ((spi_clk_rate / (cpsr * (scr + 1))) <= rate) {
				chip->div_scr = (u8)scr;
				chip->div_cpsr = (u8)cpsr;
				return 0;
			}
		}
	}

	return -EINVAL;
}

static void ep93xx_spi_cs_control(struct spi_device *spi, bool control)
{
	struct ep93xx_spi_chip *chip = spi_get_ctldata(spi);
	int value = (spi->mode & SPI_CS_HIGH) ? control : !control;

	if (chip->ops && chip->ops->cs_control)
		chip->ops->cs_control(spi, value);
}

/**
 * ep93xx_spi_setup() - setup an SPI device
 * @spi: SPI device to setup
 *
 * This function sets up SPI device mode, speed etc. Can be called multiple
 * times for a single device. Returns %0 in case of success, negative error in
 * case of failure. When this function returns success, the device is
 * deselected.
 */
static int ep93xx_spi_setup(struct spi_device *spi)
{
	struct ep93xx_spi *espi = spi_master_get_devdata(spi->master);
	struct ep93xx_spi_chip *chip;

	if (spi->bits_per_word < 4 || spi->bits_per_word > 16) {
		dev_err(&espi->pdev->dev, "invalid bits per word %d\n",
			spi->bits_per_word);
		return -EINVAL;
	}

	chip = spi_get_ctldata(spi);
	if (!chip) {
		dev_dbg(&espi->pdev->dev, "initial setup for %s\n",
			spi->modalias);

		chip = kzalloc(sizeof(*chip), GFP_KERNEL);