/*
   * 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
  ", __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
  ", __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 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;
  	int			ret_no_channel = -ENODEV;
  
  	if (!np || !name) {
  		pr_err("%s: not enough information provided
  ", __func__);
  		return ERR_PTR(-ENODEV);
  	}
  
  	count = of_property_count_strings(np, "dma-names");
  	if (count < 0) {
  		pr_err("%s: dma-names property of node '%s' missing or empty
  ",
  			__func__, np->full_name);
  		return ERR_PTR(-ENODEV);
  	}
  
  	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 {
  			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);
  }
  
  /**
   * 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);