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/*
* 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);
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