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linux-next/drivers/dma/of-dma.c
Niklas Söderlund 20ea6be6bf dmaengine: of_dma: approximate an average distribution
Currently the following DT description would result in dmac0 always
being tried first and dmac1 second if dmac0 was unavailable. This
results in heavier use of dmac0 then of dmac1. This patch adds an
approximate average distribution over the two nodes lessening the load
of anyone of them.

   i2c6: i2c@e60b0000 {
           ...
           dmas = <&dmac0 0x77>, <&dmac0 0x78>,
                  <&dmac1 0x77>, <&dmac1 0x78>;
           dma-names = "tx", "rx", "tx", "rx";
           ...
   };

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2016-05-14 13:34:10 +05:30

358 lines
10 KiB
C

/*
* 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\n", __func__,
dma_spec->np->full_name);
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 '%s' missing or empty\n",
__func__, np->full_name);
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);