/*
 * 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/mutex.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_dma.h>

static LIST_HEAD(of_dma_list);
static DEFINE_MUTEX(of_dma_lock);

/**
 * of_dma_find_controller - Get a DMA controller in DT DMA helpers list
 * @dma_spec:   pointer to DMA specifier as found in the device tree
 *
 * Finds a DMA controller with matching device node and number for dma cells
 * in a list of registered DMA controllers. If a match is found a valid pointer
 * to the DMA data stored is retuned. A NULL pointer is returned if no match is
 * found.
 */
static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
{
        struct of_dma *ofdma;

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

        pr_debug("%s: can't find DMA controller %s\n", __func__,
                 dma_spec->np->full_name);

        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;

        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;

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

        /* Now queue of_dma controller structure in list */
        mutex_lock(&of_dma_lock);
        list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
        mutex_unlock(&of_dma_lock);

        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;

        mutex_lock(&of_dma_lock);

        list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
                if (ofdma->of_node == np) {
                        list_del(&ofdma->of_dma_controllers);
                        kfree(ofdma);
                        break;
                }

        mutex_unlock(&of_dma_lock);
}
EXPORT_SYMBOL_GPL(of_dma_controller_free);

/**
 * of_dma_match_channel - Check if a DMA specifier matches name
 * @np:         device node to look for DMA channels
 * @name:       channel name to be matched
 * @index:      index of DMA specifier in list of DMA specifiers
 * @dma_spec:   pointer to DMA specifier as found in the device tree
 *
 * Check if the DMA specifier pointed to by the index in a list of DMA
 * specifiers, matches the name provided. Returns 0 if the name matches and
 * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
 */
static int of_dma_match_channel(struct device_node *np, const char *name,
                                int index, struct of_phandle_args *dma_spec)
{
        const char *s;

        if (of_property_read_string_index(np, "dma-names", index, &s))
                return -ENODEV;

        if (strcmp(name, s))
                return -ENODEV;

        if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
                                       dma_spec))
                return -ENODEV;

        return 0;
}

/**
 * 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,
                                              const char *name)
{
        struct of_phandle_args  dma_spec;
        struct of_dma           *ofdma;
        struct dma_chan         *chan;
        int                     count, i;

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

        count = of_property_count_strings(np, "dma-names");
        if (count < 0) {
                pr_err("%s: dma-names property of node '%s' missing or empty\n",
                        __func__, np->full_name);
                return NULL;
        }

        for (i = 0; i < count; i++) {
                if (of_dma_match_channel(np, name, i, &dma_spec))
                        continue;

                mutex_lock(&of_dma_lock);
                ofdma = of_dma_find_controller(&dma_spec);

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

                mutex_unlock(&of_dma_lock);

                of_node_put(dma_spec.np);

                if (chan)
                        return chan;
        }

        return NULL;
}

/**
 * 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);