268 lines
7.0 KiB
C
268 lines
7.0 KiB
C
/*
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* Device tree helpers for DMA request / controller
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*
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* Based on of_gpio.c
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*
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* Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/device.h>
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#include <linux/err.h>
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#include <linux/module.h>
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#include <linux/rculist.h>
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#include <linux/slab.h>
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#include <linux/of.h>
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#include <linux/of_dma.h>
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static LIST_HEAD(of_dma_list);
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static DEFINE_SPINLOCK(of_dma_lock);
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/**
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* of_dma_get_controller - Get a DMA controller in DT DMA helpers list
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* @dma_spec: pointer to DMA specifier as found in the device tree
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*
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* Finds a DMA controller with matching device node and number for dma cells
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* in a list of registered DMA controllers. If a match is found the use_count
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* variable is increased and a valid pointer to the DMA data stored is retuned.
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* A NULL pointer is returned if no match is found.
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*/
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static struct of_dma *of_dma_get_controller(struct of_phandle_args *dma_spec)
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{
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struct of_dma *ofdma;
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spin_lock(&of_dma_lock);
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if (list_empty(&of_dma_list)) {
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spin_unlock(&of_dma_lock);
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return NULL;
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}
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list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
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if ((ofdma->of_node == dma_spec->np) &&
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(ofdma->of_dma_nbcells == dma_spec->args_count)) {
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ofdma->use_count++;
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spin_unlock(&of_dma_lock);
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return ofdma;
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}
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spin_unlock(&of_dma_lock);
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pr_debug("%s: can't find DMA controller %s\n", __func__,
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dma_spec->np->full_name);
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return NULL;
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}
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/**
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* of_dma_put_controller - Decrement use count for a registered DMA controller
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* @of_dma: pointer to DMA controller data
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*
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* Decrements the use_count variable in the DMA data structure. This function
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* should be called only when a valid pointer is returned from
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* of_dma_get_controller() and no further accesses to data referenced by that
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* pointer are needed.
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*/
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static void of_dma_put_controller(struct of_dma *ofdma)
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{
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spin_lock(&of_dma_lock);
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ofdma->use_count--;
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spin_unlock(&of_dma_lock);
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}
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/**
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* of_dma_controller_register - Register a DMA controller to DT DMA helpers
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* @np: device node of DMA controller
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* @of_dma_xlate: translation function which converts a phandle
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* arguments list into a dma_chan structure
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* @data pointer to controller specific data to be used by
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* translation function
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*
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* Returns 0 on success or appropriate errno value on error.
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*
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* Allocated memory should be freed with appropriate of_dma_controller_free()
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* call.
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*/
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int of_dma_controller_register(struct device_node *np,
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struct dma_chan *(*of_dma_xlate)
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(struct of_phandle_args *, struct of_dma *),
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void *data)
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{
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struct of_dma *ofdma;
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int nbcells;
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if (!np || !of_dma_xlate) {
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pr_err("%s: not enough information provided\n", __func__);
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return -EINVAL;
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}
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ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
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if (!ofdma)
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return -ENOMEM;
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nbcells = be32_to_cpup(of_get_property(np, "#dma-cells", NULL));
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if (!nbcells) {
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pr_err("%s: #dma-cells property is missing or invalid\n",
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__func__);
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kfree(ofdma);
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return -EINVAL;
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}
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ofdma->of_node = np;
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ofdma->of_dma_nbcells = nbcells;
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ofdma->of_dma_xlate = of_dma_xlate;
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ofdma->of_dma_data = data;
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ofdma->use_count = 0;
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/* Now queue of_dma controller structure in list */
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spin_lock(&of_dma_lock);
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list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
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spin_unlock(&of_dma_lock);
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return 0;
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}
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EXPORT_SYMBOL_GPL(of_dma_controller_register);
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/**
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* of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
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* @np: device node of DMA controller
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*
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* Memory allocated by of_dma_controller_register() is freed here.
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*/
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int of_dma_controller_free(struct device_node *np)
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{
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struct of_dma *ofdma;
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spin_lock(&of_dma_lock);
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if (list_empty(&of_dma_list)) {
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spin_unlock(&of_dma_lock);
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return -ENODEV;
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}
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list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
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if (ofdma->of_node == np) {
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if (ofdma->use_count) {
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spin_unlock(&of_dma_lock);
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return -EBUSY;
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}
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list_del(&ofdma->of_dma_controllers);
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spin_unlock(&of_dma_lock);
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kfree(ofdma);
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return 0;
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}
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spin_unlock(&of_dma_lock);
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return -ENODEV;
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}
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EXPORT_SYMBOL_GPL(of_dma_controller_free);
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/**
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* of_dma_match_channel - Check if a DMA specifier matches name
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* @np: device node to look for DMA channels
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* @name: channel name to be matched
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* @index: index of DMA specifier in list of DMA specifiers
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* @dma_spec: pointer to DMA specifier as found in the device tree
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*
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* Check if the DMA specifier pointed to by the index in a list of DMA
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* specifiers, matches the name provided. Returns 0 if the name matches and
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* a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
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*/
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static int of_dma_match_channel(struct device_node *np, char *name, int index,
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struct of_phandle_args *dma_spec)
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{
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const char *s;
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if (of_property_read_string_index(np, "dma-names", index, &s))
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return -ENODEV;
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if (strcmp(name, s))
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return -ENODEV;
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if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
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dma_spec))
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return -ENODEV;
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return 0;
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}
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/**
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* of_dma_request_slave_channel - Get the DMA slave channel
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* @np: device node to get DMA request from
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* @name: name of desired channel
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*
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* Returns pointer to appropriate dma channel on success or NULL on error.
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*/
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struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
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char *name)
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{
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struct of_phandle_args dma_spec;
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struct of_dma *ofdma;
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struct dma_chan *chan;
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int count, i;
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if (!np || !name) {
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pr_err("%s: not enough information provided\n", __func__);
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return NULL;
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}
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count = of_property_count_strings(np, "dma-names");
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if (count < 0) {
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pr_err("%s: dma-names property missing or empty\n", __func__);
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return NULL;
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}
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for (i = 0; i < count; i++) {
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if (of_dma_match_channel(np, name, i, &dma_spec))
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continue;
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ofdma = of_dma_get_controller(&dma_spec);
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if (!ofdma)
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continue;
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chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
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of_dma_put_controller(ofdma);
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of_node_put(dma_spec.np);
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if (chan)
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return chan;
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}
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return NULL;
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}
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/**
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* of_dma_simple_xlate - Simple DMA engine translation function
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* @dma_spec: pointer to DMA specifier as found in the device tree
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* @of_dma: pointer to DMA controller data
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*
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* A simple translation function for devices that use a 32-bit value for the
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* filter_param when calling the DMA engine dma_request_channel() function.
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* Note that this translation function requires that #dma-cells is equal to 1
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* and the argument of the dma specifier is the 32-bit filter_param. Returns
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* pointer to appropriate dma channel on success or NULL on error.
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*/
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struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
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struct of_dma *ofdma)
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{
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int count = dma_spec->args_count;
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struct of_dma_filter_info *info = ofdma->of_dma_data;
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if (!info || !info->filter_fn)
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return NULL;
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if (count != 1)
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return NULL;
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return dma_request_channel(info->dma_cap, info->filter_fn,
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&dma_spec->args[0]);
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}
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EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
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