spi.c

TI的达芬奇系列dm355使用的spi模块驱动

/*-------------------------------------------------------------------------*/

static void spi_master_release(struct class_device *cdev)
{
	struct spi_master *master;

	master = container_of(cdev, struct spi_master, cdev);
	kfree(master);
}

static struct class spi_master_class = {
	.name		= "spi_master",
	.release	= spi_master_release,
};


/**
 * spi_alloc_master - allocate SPI master controller
 * @dev: the controller, possibly using the platform_bus
 * @size: how much driver-private data to preallocate; the pointer to this
 * 	memory is in the class_data field of the returned class_device,
 *	accessible with spi_master_get_devdata().
 *
 * This call is used only by SPI master controller drivers, which are the
 * only ones directly touching chip registers.  It's how they allocate
 * an spi_master structure, prior to calling spi_add_master().
 *
 * This must be called from context that can sleep.  It returns the SPI
 * master structure on success, else NULL.
 *
 * The caller is responsible for assigning the bus number and initializing
 * the master's methods before calling spi_add_master(); and (after errors
 * adding the device) calling spi_master_put() to prevent a memory leak.
 */
struct spi_master * __init_or_module
spi_alloc_master(struct device *dev, unsigned size)
{
	struct spi_master	*master;

	if (!dev)
		return NULL;

	master = kzalloc(size + sizeof *master, SLAB_KERNEL);
	if (!master)
		return NULL;

	class_device_initialize(&master->cdev);
	master->cdev.class = &spi_master_class;
	master->cdev.dev = get_device(dev);
	spi_master_set_devdata(master, &master[1]);

	return master;
}
EXPORT_SYMBOL_GPL(spi_alloc_master);

/**
 * spi_register_master - register SPI master controller
 * @master: initialized master, originally from spi_alloc_master()
 *
 * SPI master controllers connect to their drivers using some non-SPI bus,
 * such as the platform bus.  The final stage of probe() in that code
 * includes calling spi_register_master() to hook up to this SPI bus glue.
 *
 * SPI controllers use board specific (often SOC specific) bus numbers,
 * and board-specific addressing for SPI devices combines those numbers
 * with chip select numbers.  Since SPI does not directly support dynamic
 * device identification, boards need configuration tables telling which
 * chip is at which address.
 *
 * This must be called from context that can sleep.  It returns zero on
 * success, else a negative error code (dropping the master's refcount).
 * After a successful return, the caller is responsible for calling
 * spi_unregister_master().
 */
int __init_or_module
spi_register_master(struct spi_master *master)
{
	static atomic_t		dyn_bus_id = ATOMIC_INIT(0);
	struct device		*dev = master->cdev.dev;
	int			status = -ENODEV;
	int			dynamic = 0;

	if (!dev)
		return -ENODEV;

	/* convention:  dynamically assigned bus IDs count down from the max */
	if (master->bus_num == 0) {
		master->bus_num = atomic_dec_return(&dyn_bus_id);
		dynamic = 1;
	}

	/* register the device, then userspace will see it.
	 * registration fails if the bus ID is in use.
	 */
	snprintf(master->cdev.class_id, sizeof master->cdev.class_id,
		"spi%u", master->bus_num);
	status = class_device_add(&master->cdev);
	if (status < 0)
		goto done;
	dev_dbg(dev, "registered master %s%s\n", master->cdev.class_id,
			dynamic ? " (dynamic)" : "");

	/* populate children from any spi device tables */
	scan_boardinfo(master);
	status = 0;
done:
	return status;
}
EXPORT_SYMBOL_GPL(spi_register_master);


static int __unregister(struct device *dev, void *unused)
{
	/* note: before about 2.6.14-rc1 this would corrupt memory: */
	spi_unregister_device(to_spi_device(dev));
	return 0;
}

/**
 * spi_unregister_master - unregister SPI master controller
 * @master: the master being unregistered
 *
 * This call is used only by SPI master controller drivers, which are the
 * only ones directly touching chip registers.
 *
 * This must be called from context that can sleep.
 */
void spi_unregister_master(struct spi_master *master)
{
	(void) device_for_each_child(master->cdev.dev, NULL, __unregister);
	class_device_unregister(&master->cdev);
	master->cdev.dev = NULL;
}
EXPORT_SYMBOL_GPL(spi_unregister_master);

/**
 * spi_busnum_to_master - look up master associated with bus_num
 * @bus_num: the master's bus number
 *
 * This call may be used with devices that are registered after
 * arch init time.  It returns a refcounted pointer to the relevant
 * spi_master (which the caller must release), or NULL if there is
 * no such master registered.
 */
struct spi_master *spi_busnum_to_master(u16 bus_num)
{
	if (bus_num) {
		char			name[8];
		struct kobject		*bus;

		snprintf(name, sizeof name, "spi%u", bus_num);
		bus = kset_find_obj(&spi_master_class.subsys.kset, name);
		if (bus)
			return container_of(bus, struct spi_master, cdev.kobj);
	}
	return NULL;
}
EXPORT_SYMBOL_GPL(spi_busnum_to_master);


/*-------------------------------------------------------------------------*/

static void spi_complete(void *arg)
{
	complete(arg);
}

/**
 * spi_sync - blocking/synchronous SPI data transfers
 * @spi: device with which data will be exchanged
 * @message: describes the data transfers
 *
 * This call may only be used from a context that may sleep.  The sleep
 * is non-interruptible, and has no timeout.  Low-overhead controller
 * drivers may DMA directly into and out of the message buffers.
 *
 * Note that the SPI device's chip select is active during the message,
 * and then is normally disabled between messages.  Drivers for some
 * frequently-used devices may want to minimize costs of selecting a chip,
 * by leaving it selected in anticipation that the next message will go
 * to the same chip.  (That may increase power usage.)
 *
 * Also, the caller is guaranteeing that the memory associated with the
 * message will not be freed before this call returns.
 *
 * The return value is a negative error code if the message could not be
 * submitted, else zero.  When the value is zero, then message->status is
 * also defined:  it's the completion code for the transfer, either zero
 * or a negative error code from the controller driver.
 */
int spi_sync(struct spi_device *spi, struct spi_message *message)
{
	DECLARE_COMPLETION(done);
	int status;

	message->complete = spi_complete;
	message->context = &done;
	status = spi_async(spi, message);
	if (status == 0)
		wait_for_completion(&done);
	message->context = NULL;
	return status;
}
EXPORT_SYMBOL_GPL(spi_sync);

#define	SPI_BUFSIZ	(SMP_CACHE_BYTES)

static u8	*buf;

/**
 * spi_write_then_read - SPI synchronous write followed by read
 * @spi: device with which data will be exchanged
 * @txbuf: data to be written (need not be dma-safe)
 * @n_tx: size of txbuf, in bytes
 * @rxbuf: buffer into which data will be read
 * @n_rx: size of rxbuf, in bytes (need not be dma-safe)
 *
 * This performs a half duplex MicroWire style transaction with the
 * device, sending txbuf and then reading rxbuf.  The return value
 * is zero for success, else a negative errno status code.
 * This call may only be used from a context that may sleep.
 *
 * Parameters to this routine are always copied using a small buffer;
 * performance-sensitive or bulk transfer code should instead use
 * spi_{async,sync}() calls with dma-safe buffers.
 */
int spi_write_then_read(struct spi_device *spi,
		const u8 *txbuf, unsigned n_tx,
		u8 *rxbuf, unsigned n_rx)
{
	static DECLARE_MUTEX(lock);

	int			status;
	struct spi_message	message;
	struct spi_transfer	x[2];
	u8			*local_buf;

	/* Use preallocated DMA-safe buffer.  We can't avoid copying here,
	 * (as a pure convenience thing), but we can keep heap costs
	 * out of the hot path ...
	 */
	if ((n_tx + n_rx) > SPI_BUFSIZ)
		return -EINVAL;

	spi_message_init(&message);
	memset(x, 0, sizeof x);
	if (n_tx) {
		x[0].len = n_tx;
		spi_message_add_tail(&x[0], &message);
	}
	if (n_rx) {
		x[1].len = n_rx;
		spi_message_add_tail(&x[1], &message);
	}

	/* ... unless someone else is using the pre-allocated buffer */
	if (down_trylock(&lock)) {
		local_buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
		if (!local_buf)
			return -ENOMEM;
	} else
		local_buf = buf;

	memcpy(local_buf, txbuf, n_tx);
	x[0].tx_buf = local_buf;
	x[1].rx_buf = local_buf + n_tx;

	/* do the i/o */
	status = spi_sync(spi, &message);
	if (status == 0) {
		memcpy(rxbuf, x[1].rx_buf, n_rx);
		status = message.status;
	}

	if (x[0].tx_buf == buf)
		up(&lock);
	else
		kfree(local_buf);

	return status;
}
EXPORT_SYMBOL_GPL(spi_write_then_read);

/*-------------------------------------------------------------------------*/

static int __init spi_init(void)
{
	int	status;

	buf = kmalloc(SPI_BUFSIZ, SLAB_KERNEL);
	if (!buf) {
		status = -ENOMEM;
		goto err0;
	}

	status = bus_register(&spi_bus_type);
	if (status < 0)
		goto err1;

	status = class_register(&spi_master_class);
	if (status < 0)
		goto err2;
	return 0;

err2:
	bus_unregister(&spi_bus_type);
err1:
	kfree(buf);
	buf = NULL;
err0:
	return status;
}

/* board_info is normally registered in arch_initcall(),
 * but even essential drivers wait till later
 *
 * REVISIT only boardinfo really needs static linking. the rest (device and
 * driver registration) _could_ be dynamically linked (modular) ... costs
 * include needing to have boardinfo data structures be much more public.
 */
subsys_initcall(spi_init);