linux/drivers/dma/of-dma.c
Stephen Warren 0ad7c00057 dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel
lookup fails. Lookup could fail for two distinct reasons:

a) No DMA specification exists for the channel name.
   This includes situations where no DMA specifications exist at all, or
   other general lookup problems.

b) A DMA specification does exist, yet the driver for that channel is not
   yet registered.

Case (b) should trigger deferred probe in client drivers. However, since
they have no way to differentiate the two situations, it cannot.

Implement new function dma_request_slave_channel_reason(), which performs
identically to dma_request_slave_channel(), except that it returns an
error-pointer rather than NULL, which allows callers to detect when
deferred probe should occur.

Eventually, all drivers should be converted to this new API, the old API
removed, and the new API renamed to the more desirable name. This patch
doesn't convert the existing API and all drivers in one go, since some
drivers call dma_request_slave_channel() then dma_request_channel() if
that fails. That would require either modifying dma_request_channel() in
the same way, or adding extra error-handling code to all affected
drivers, and there are close to 100 drivers using the other API, rather
than just the 15-20 or so that use dma_request_slave_channel(), which
might be tenable in a single patch.

acpi_dma_request_slave_chan_by_name() doesn't currently implement
deferred probe. It should, but this will be addressed later.

Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-12-10 17:46:48 +05:30

221 lines
5.9 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_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_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\n", __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\n",
__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);