/*
 * 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 %pOF\n", __func__,
                 dma_spec->np);

        return NULL;
}

/**
 * of_dma_router_xlate - translation function for router devices
 * @dma_spec:   pointer to DMA specifier as found in the device tree
 * @of_dma:     pointer to DMA controller data (router information)
 *
 * The function creates new dma_spec to be passed to the router driver's
 * of_dma_route_allocate() function to prepare a dma_spec which will be used
 * to request channel from the real DMA controller.
 */
static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
                                            struct of_dma *ofdma)
{
        struct dma_chan         *chan;
        struct of_dma           *ofdma_target;
        struct of_phandle_args  dma_spec_target;
        void                    *route_data;

        /* translate the request for the real DMA controller */
        memcpy(&dma_spec_target, dma_spec, sizeof(dma_spec_target));
        route_data = ofdma->of_dma_route_allocate(&dma_spec_target, ofdma);
        if (IS_ERR(route_data))
                return NULL;

        ofdma_target = of_dma_find_controller(&dma_spec_target);
        if (!ofdma_target)
                return NULL;

        chan = ofdma_target->of_dma_xlate(&dma_spec_target, ofdma_target);
        if (chan) {
                chan->router = ofdma->dma_router;
                chan->route_data = route_data;
        } else {
                ofdma->dma_router->route_free(ofdma->dma_router->dev,
                                              route_data);
        }

        /*
         * Need to put the node back since the ofdma->of_dma_route_allocate
         * has taken it for generating the new, translated dma_spec
         */
        of_node_put(dma_spec_target.np);
        return chan;
}

/**
 * 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_router_register - Register a DMA router to DT DMA helpers as a
 *                          controller
 * @np:                         device node of DMA router
 * @of_dma_route_allocate:      setup function for the router which need to
 *                              modify the dma_spec for the DMA controller to
 *                              use and to set up the requested route.
 * @dma_router:                 pointer to dma_router structure to be used when
 *                              the route need to be free up.
 *
 * 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_router_register(struct device_node *np,
                           void *(*of_dma_route_allocate)
                           (struct of_phandle_args *, struct of_dma *),
                           struct dma_router *dma_router)
{
        struct of_dma   *ofdma;

        if (!np || !of_dma_route_allocate || !dma_router) {
                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_router_xlate;
        ofdma->of_dma_route_allocate = of_dma_route_allocate;
        ofdma->dma_router = dma_router;

        /* 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_router_register);

/**
 * 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 an error pointer.
 */
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, start;
        int                     ret_no_channel = -ENODEV;
        static atomic_t         last_index;

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

        /* Silently fail if there is not even the "dmas" property */
        if (!of_find_property(np, "dmas", NULL))
                return ERR_PTR(-ENODEV);

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

        /*
         * approximate an average distribution across multiple
         * entries with the same name
         */
        start = atomic_inc_return(&last_index);
        for (i = 0; i < count; i++) {
                if (of_dma_match_channel(np, name,
                                         (i + start) % count,
                                         &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 {
                        ret_no_channel = -EPROBE_DEFER;
                        chan = NULL;
                }

                mutex_unlock(&of_dma_lock);

                of_node_put(dma_spec.np);

                if (chan)
                        return chan;
        }

        return ERR_PTR(ret_no_channel);
}
EXPORT_SYMBOL_GPL(of_dma_request_slave_channel);

/**
 * 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);

/**
 * of_dma_xlate_by_chan_id - Translate dt property to DMA channel by channel id
 * @dma_spec:   pointer to DMA specifier as found in the device tree
 * @of_dma:     pointer to DMA controller data
 *
 * This function can be used as the of xlate callback for DMA driver which wants
 * to match the channel based on the channel id. When using this xlate function
 * the #dma-cells propety of the DMA controller dt node needs to be set to 1.
 * The data parameter of of_dma_controller_register must be a pointer to the
 * dma_device struct the function should match upon.
 *
 * Returns pointer to appropriate dma channel on success or NULL on error.
 */
struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
                                         struct of_dma *ofdma)
{
        struct dma_device *dev = ofdma->of_dma_data;
        struct dma_chan *chan, *candidate = NULL;

        if (!dev || dma_spec->args_count != 1)
                return NULL;

        list_for_each_entry(chan, &dev->channels, device_node)
                if (chan->chan_id == dma_spec->args[0]) {
                        candidate = chan;
                        break;
                }

        if (!candidate)
                return NULL;

        return dma_get_slave_channel(candidate);
}
EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);