linux/drivers/of/dma.c

/*
 * Device tree helpers for DMA request / controller
 *
 * Based on of_gpio.c
 *
 * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
 *
 * 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/device.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/rculist.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_dma.h>

static LIST_HEAD(of_dma_list);

/**
 * of_dma_find_controller - Find a DMA controller in DT DMA helpers list
 * @np:		device node of DMA controller
 */
static struct of_dma *of_dma_find_controller(struct device_node *np)
{
	struct of_dma *ofdma;

	if (list_empty(&of_dma_list)) {
		pr_err("empty DMA controller list\n");
		return NULL;
	}

	list_for_each_entry_rcu(ofdma, &of_dma_list, of_dma_controllers)
		if (ofdma->of_node == np)
			return ofdma;

	return NULL;
}

/**
 * of_dma_controller_register - Register a DMA controller to DT DMA helpers
 * @np:			device node of DMA controller
 * @of_dma_xlate:	translation function which converts a phandle
 *			arguments list into a dma_chan structure
 * @data		pointer to controller specific data to be used by
 *			translation function
 *
 * Returns 0 on success or appropriate errno value on error.
 *
 * Allocated memory should be freed with appropriate of_dma_controller_free()
 * call.
 */
int of_dma_controller_register(struct device_node *np,
				struct dma_chan *(*of_dma_xlate)
				(struct of_phandle_args *, struct of_dma *),
				void *data)
{
	struct of_dma	*ofdma;
	int		nbcells;

	if (!np || !of_dma_xlate) {
		pr_err("%s: not enough information provided\n", __func__);
		return -EINVAL;
	}

	ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
	if (!ofdma)
		return -ENOMEM;

	nbcells = be32_to_cpup(of_get_property(np, "#dma-cells", NULL));
	if (!nbcells) {
		pr_err("%s: #dma-cells property is missing or invalid\n",
		       __func__);
		return -EINVAL;
	}

	ofdma->of_node = np;
	ofdma->of_dma_nbcells = nbcells;
	ofdma->of_dma_xlate = of_dma_xlate;
	ofdma->of_dma_data = data;

	/* Now queue of_dma controller structure in list */
	list_add_tail_rcu(&ofdma->of_dma_controllers, &of_dma_list);

	return 0;
}
EXPORT_SYMBOL_GPL(of_dma_controller_register);

/**
 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
 * @np:		device node of DMA controller
 *
 * Memory allocated by of_dma_controller_register() is freed here.
 */
void of_dma_controller_free(struct device_node *np)
{
	struct of_dma *ofdma;

	ofdma = of_dma_find_controller(np);
	if (ofdma) {
		list_del_rcu(&ofdma->of_dma_controllers);
		kfree(ofdma);
	}
}
EXPORT_SYMBOL_GPL(of_dma_controller_free);

/**
 * of_dma_find_channel - Find a DMA channel by name
 * @np:		device node to look for DMA channels
 * @name:	name of desired channel
 * @dma_spec:	pointer to DMA specifier as found in the device tree
 *
 * Find a DMA channel by the name. Returns 0 on success or appropriate
 * errno value on error.
 */
static int of_dma_find_channel(struct device_node *np, char *name,
			       struct of_phandle_args *dma_spec)
{
	int count, i;
	const char *s;

	count = of_property_count_strings(np, "dma-names");
	if (count < 0)
		return count;

	for (i = 0; i < count; i++) {
		if (of_property_read_string_index(np, "dma-names", i, &s))
			continue;

		if (strcmp(name, s))
			continue;

		if (!of_parse_phandle_with_args(np, "dmas", "#dma-cells", i,
						dma_spec))
			return 0;
	}

	return -ENODEV;
}

/**
 * of_dma_request_slave_channel - Get the DMA slave channel
 * @np:		device node to get DMA request from
 * @name:	name of desired channel
 *
 * Returns pointer to appropriate dma channel on success or NULL on error.
 */
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
					      char *name)
{
	struct of_phandle_args	dma_spec;
	struct of_dma		*ofdma;
	struct dma_chan		*chan;
	int			r;

	if (!np || !name) {
		pr_err("%s: not enough information provided\n", __func__);
		return NULL;
	}

	do {
		r = of_dma_find_channel(np, name, &dma_spec);
		if (r) {
			pr_err("%s: can't find DMA channel\n", np->full_name);
			return NULL;
		}

		ofdma = of_dma_find_controller(dma_spec.np);
		if (!ofdma) {
			pr_debug("%s: can't find DMA controller %s\n",
				 np->full_name, dma_spec.np->full_name);
			continue;
		}

		if (dma_spec.args_count != ofdma->of_dma_nbcells) {
			pr_debug("%s: wrong #dma-cells for %s\n", np->full_name,
				 dma_spec.np->full_name);
			continue;
		}

		chan = ofdma->of_dma_xlate(&dma_spec, ofdma);

		of_node_put(dma_spec.np);

	} while (!chan);

	return chan;
}

/**
 * of_dma_simple_xlate - Simple DMA engine translation function
 * @dma_spec:	pointer to DMA specifier as found in the device tree
 * @of_dma:	pointer to DMA controller data
 *
 * A simple translation function for devices that use a 32-bit value for the
 * filter_param when calling the DMA engine dma_request_channel() function.
 * Note that this translation function requires that #dma-cells is equal to 1
 * and the argument of the dma specifier is the 32-bit filter_param. Returns
 * pointer to appropriate dma channel on success or NULL on error.
 */
struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
						struct of_dma *ofdma)
{
	int count = dma_spec->args_count;
	struct of_dma_filter_info *info = ofdma->of_dma_data;

	if (!info || !info->filter_fn)
		return NULL;

	if (count != 1)
		return NULL;

	return dma_request_channel(info->dma_cap, info->filter_fn,
			&dma_spec->args[0]);
}
EXPORT_SYMBOL_GPL(of_dma_simple_xlate);