linux/arch/sh/drivers/dma/dma-api.c

293 lines
7.1 KiB
C

/*
* arch/sh/drivers/dma/dma-api.c
*
* SuperH-specific DMA management API
*
* Copyright (C) 2003, 2004 Paul Mundt
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/proc_fs.h>
#include <linux/list.h>
#include <asm/dma.h>
DEFINE_SPINLOCK(dma_spin_lock);
static LIST_HEAD(registered_dmac_list);
/*
* A brief note about the reasons for this API as it stands.
*
* For starters, the old ISA DMA API didn't work for us for a number of
* reasons, for one, the vast majority of channels on the SH DMAC are
* dual-address mode only, and both the new and the old DMA APIs are after the
* concept of managing a DMA buffer, which doesn't overly fit this model very
* well. In addition to which, the new API is largely geared at IOMMUs and
* GARTs, and doesn't even support the channel notion very well.
*
* The other thing that's a marginal issue, is the sheer number of random DMA
* engines that are present (ie, in boards like the Dreamcast), some of which
* cascade off of the SH DMAC, and others do not. As such, there was a real
* need for a scalable subsystem that could deal with both single and
* dual-address mode usage, in addition to interoperating with cascaded DMACs.
*
* There really isn't any reason why this needs to be SH specific, though I'm
* not aware of too many other processors (with the exception of some MIPS)
* that have the same concept of a dual address mode, or any real desire to
* actually make use of the DMAC even if such a subsystem were exposed
* elsewhere.
*
* The idea for this was derived from the ARM port, which acted as an excellent
* reference when trying to address these issues.
*
* It should also be noted that the decision to add Yet Another DMA API(tm) to
* the kernel wasn't made easily, and was only decided upon after conferring
* with jejb with regards to the state of the old and new APIs as they applied
* to these circumstances. Philip Blundell was also a great help in figuring
* out some single-address mode DMA semantics that were otherwise rather
* confusing.
*/
struct dma_info *get_dma_info(unsigned int chan)
{
struct list_head *pos, *tmp;
unsigned int total = 0;
/*
* Look for each DMAC's range to determine who the owner of
* the channel is.
*/
list_for_each_safe(pos, tmp, &registered_dmac_list) {
struct dma_info *info = list_entry(pos, struct dma_info, list);
total += info->nr_channels;
if (chan > total)
continue;
return info;
}
return NULL;
}
struct dma_channel *get_dma_channel(unsigned int chan)
{
struct dma_info *info = get_dma_info(chan);
if (!info)
return ERR_PTR(-EINVAL);
return info->channels + chan;
}
int get_dma_residue(unsigned int chan)
{
struct dma_info *info = get_dma_info(chan);
struct dma_channel *channel = &info->channels[chan];
if (info->ops->get_residue)
return info->ops->get_residue(channel);
return 0;
}
int request_dma(unsigned int chan, const char *dev_id)
{
struct dma_info *info = get_dma_info(chan);
struct dma_channel *channel = &info->channels[chan];
down(&channel->sem);
if (!info->ops || chan >= MAX_DMA_CHANNELS) {
up(&channel->sem);
return -EINVAL;
}
atomic_set(&channel->busy, 1);
strlcpy(channel->dev_id, dev_id, sizeof(channel->dev_id));
up(&channel->sem);
if (info->ops->request)
return info->ops->request(channel);
return 0;
}
void free_dma(unsigned int chan)
{
struct dma_info *info = get_dma_info(chan);
struct dma_channel *channel = &info->channels[chan];
if (info->ops->free)
info->ops->free(channel);
atomic_set(&channel->busy, 0);
}
void dma_wait_for_completion(unsigned int chan)
{
struct dma_info *info = get_dma_info(chan);
struct dma_channel *channel = &info->channels[chan];
if (channel->flags & DMA_TEI_CAPABLE) {
wait_event(channel->wait_queue,
(info->ops->get_residue(channel) == 0));
return;
}
while (info->ops->get_residue(channel))
cpu_relax();
}
void dma_configure_channel(unsigned int chan, unsigned long flags)
{
struct dma_info *info = get_dma_info(chan);
struct dma_channel *channel = &info->channels[chan];
if (info->ops->configure)
info->ops->configure(channel, flags);
}
int dma_xfer(unsigned int chan, unsigned long from,
unsigned long to, size_t size, unsigned int mode)
{
struct dma_info *info = get_dma_info(chan);
struct dma_channel *channel = &info->channels[chan];
channel->sar = from;
channel->dar = to;
channel->count = size;
channel->mode = mode;
return info->ops->xfer(channel);
}
#ifdef CONFIG_PROC_FS
static int dma_read_proc(char *buf, char **start, off_t off,
int len, int *eof, void *data)
{
struct list_head *pos, *tmp;
char *p = buf;
if (list_empty(&registered_dmac_list))
return 0;
/*
* Iterate over each registered DMAC
*/
list_for_each_safe(pos, tmp, &registered_dmac_list) {
struct dma_info *info = list_entry(pos, struct dma_info, list);
int i;
/*
* Iterate over each channel
*/
for (i = 0; i < info->nr_channels; i++) {
struct dma_channel *channel = info->channels + i;
if (!(channel->flags & DMA_CONFIGURED))
continue;
p += sprintf(p, "%2d: %14s %s\n", i,
info->name, channel->dev_id);
}
}
return p - buf;
}
#endif
int __init register_dmac(struct dma_info *info)
{
int i;
INIT_LIST_HEAD(&info->list);
printk(KERN_INFO "DMA: Registering %s handler (%d channel%s).\n",
info->name, info->nr_channels,
info->nr_channels > 1 ? "s" : "");
BUG_ON((info->flags & DMAC_CHANNELS_CONFIGURED) && !info->channels);
/*
* Don't touch pre-configured channels
*/
if (!(info->flags & DMAC_CHANNELS_CONFIGURED)) {
unsigned int size;
size = sizeof(struct dma_channel) * info->nr_channels;
info->channels = kmalloc(size, GFP_KERNEL);
if (!info->channels)
return -ENOMEM;
memset(info->channels, 0, size);
}
for (i = 0; i < info->nr_channels; i++) {
struct dma_channel *chan = info->channels + i;
chan->chan = i;
memcpy(chan->dev_id, "Unused", 7);
if (info->flags & DMAC_CHANNELS_TEI_CAPABLE)
chan->flags |= DMA_TEI_CAPABLE;
init_MUTEX(&chan->sem);
init_waitqueue_head(&chan->wait_queue);
#ifdef CONFIG_SYSFS
dma_create_sysfs_files(chan);
#endif
}
list_add(&info->list, &registered_dmac_list);
return 0;
}
void __exit unregister_dmac(struct dma_info *info)
{
if (!(info->flags & DMAC_CHANNELS_CONFIGURED))
kfree(info->channels);
list_del(&info->list);
}
static int __init dma_api_init(void)
{
printk("DMA: Registering DMA API.\n");
#ifdef CONFIG_PROC_FS
create_proc_read_entry("dma", 0, 0, dma_read_proc, 0);
#endif
return 0;
}
subsys_initcall(dma_api_init);
MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
MODULE_DESCRIPTION("DMA API for SuperH");
MODULE_LICENSE("GPL");
EXPORT_SYMBOL(request_dma);
EXPORT_SYMBOL(free_dma);
EXPORT_SYMBOL(register_dmac);
EXPORT_SYMBOL(get_dma_residue);
EXPORT_SYMBOL(get_dma_info);
EXPORT_SYMBOL(get_dma_channel);
EXPORT_SYMBOL(dma_xfer);
EXPORT_SYMBOL(dma_wait_for_completion);
EXPORT_SYMBOL(dma_configure_channel);