linux/drivers/dma/of-dma.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Device tree helpers for DMA request / controller
 *
 * Based on of_gpio.c
 *
 * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
 */

#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>

#include "dmaengine.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 returned. A NULL pointer is returned if no match is
 * found.
 */
static struct of_dma *of_dma_find_controller(const struct of_phandle_args *dma_spec)
{ … }

/**
 * of_dma_router_xlate - translation function for router devices
 * @dma_spec:	pointer to DMA specifier as found in the device tree
 * @ofdma:	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)
{ … }

/**
 * 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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * 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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * 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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * 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)
{ … }

/**
 * 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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * of_dma_simple_xlate - Simple DMA engine translation function
 * @dma_spec:	pointer to DMA specifier as found in the device tree
 * @ofdma:	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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * 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
 * @ofdma:	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 property 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)
{ … }
EXPORT_SYMBOL_GPL(…);