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dmaengine: introduce dma_request_channel and private channels

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This interface is primarily for device-to-memory clients which need to
search for dma channels with platform-specific characteristics.  The
prototype is:

struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
                                     dma_filter_fn filter_fn,
                                     void *filter_param);

When the optional 'filter_fn' parameter is set to NULL
dma_request_channel simply returns the first channel that satisfies the
capability mask.  Otherwise, when the mask parameter is insufficient for
specifying the necessary channel, the filter_fn routine can be used to
disposition the available channels in the system. The filter_fn routine
is called once for each free channel in the system.  Upon seeing a
suitable channel filter_fn returns DMA_ACK which flags that channel to
be the return value from dma_request_channel.  A channel allocated via
this interface is exclusive to the caller, until dma_release_channel()
is called.

To ensure that all channels are not consumed by the general-purpose
allocator the DMA_PRIVATE capability is provided to exclude a dma_device
from general-purpose (memory-to-memory) consideration.

Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams 2009-01-06 11:38:15 -07:00
parent f67b459992
commit 59b5ec2144
2 changed files with 155 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

155
drivers/dma/dmaengine.c
View File

@ -134,14 +134,14 @@ static struct class dma_devclass = {
/* --- client and device registration --- */
#define dma_chan_satisfies_mask(chan, mask) \
__dma_chan_satisfies_mask((chan), &(mask))
#define dma_device_satisfies_mask(device, mask) \
__dma_device_satisfies_mask((device), &(mask))
static int
__dma_chan_satisfies_mask(struct dma_chan *chan, dma_cap_mask_t *want)
__dma_device_satisfies_mask(struct dma_device *device, dma_cap_mask_t *want)
{
dma_cap_mask_t has;
bitmap_and(has.bits, want->bits, chan->device->cap_mask.bits,
bitmap_and(has.bits, want->bits, device->cap_mask.bits,
DMA_TX_TYPE_END);
return bitmap_equal(want->bits, has.bits, DMA_TX_TYPE_END);
}
@ -195,7 +195,7 @@ static int dma_chan_get(struct dma_chan *chan)
err = desc_cnt;
chan->client_count = 0;
module_put(owner);
} else
} else if (!dma_has_cap(DMA_PRIVATE, chan->device->cap_mask))
balance_ref_count(chan);
}
@ -232,14 +232,16 @@ static void dma_client_chan_alloc(struct dma_client *client)
/* Find a channel */
list_for_each_entry(device, &dma_device_list, global_node) {
if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
continue;
/* Does the client require a specific DMA controller? */
if (client->slave && client->slave->dma_dev
&& client->slave->dma_dev != device->dev)
continue;
if (!dma_device_satisfies_mask(device, client->cap_mask))
continue;
list_for_each_entry(chan, &device->channels, device_node) {
if (!dma_chan_satisfies_mask(chan, client->cap_mask))
continue;
if (!chan->client_count)
continue;
ack = client->event_callback(client, chan,
@ -320,11 +322,12 @@ static int __init dma_channel_table_init(void)
bitmap_fill(dma_cap_mask_all.bits, DMA_TX_TYPE_END);
/* 'interrupt' and 'slave' are channel capabilities, but are not
* associated with an operation so they do not need an entry in the
* channel_table
/* 'interrupt', 'private', and 'slave' are channel capabilities,
* but are not associated with an operation so they do not need
* an entry in the channel_table
*/
clear_bit(DMA_INTERRUPT, dma_cap_mask_all.bits);
clear_bit(DMA_PRIVATE, dma_cap_mask_all.bits);
clear_bit(DMA_SLAVE, dma_cap_mask_all.bits);
for_each_dma_cap_mask(cap, dma_cap_mask_all) {
@ -378,10 +381,13 @@ void dma_issue_pending_all(void)
"client called %s without a reference", __func__);
rcu_read_lock();
list_for_each_entry_rcu(device, &dma_device_list, global_node)
list_for_each_entry_rcu(device, &dma_device_list, global_node) {
if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
continue;
list_for_each_entry(chan, &device->channels, device_node)
if (chan->client_count)
device->device_issue_pending(chan);
}
rcu_read_unlock();
}
EXPORT_SYMBOL(dma_issue_pending_all);
@ -403,7 +409,8 @@ static struct dma_chan *nth_chan(enum dma_transaction_type cap, int n)
struct dma_chan *min = NULL;
list_for_each_entry(device, &dma_device_list, global_node) {
if (!dma_has_cap(cap, device->cap_mask))
if (!dma_has_cap(cap, device->cap_mask) ||
dma_has_cap(DMA_PRIVATE, device->cap_mask))
continue;
list_for_each_entry(chan, &device->channels, device_node) {
if (!chan->client_count)
@ -452,9 +459,12 @@ static void dma_channel_rebalance(void)
for_each_possible_cpu(cpu)
per_cpu_ptr(channel_table[cap], cpu)->chan = NULL;
list_for_each_entry(device, &dma_device_list, global_node)
list_for_each_entry(device, &dma_device_list, global_node) {
if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
continue;
list_for_each_entry(chan, &device->channels, device_node)
chan->table_count = 0;
}
/* don't populate the channel_table if no clients are available */
if (!dmaengine_ref_count)
@ -473,6 +483,111 @@ static void dma_channel_rebalance(void)
}
}
static struct dma_chan *private_candidate(dma_cap_mask_t *mask, struct dma_device *dev)
{
struct dma_chan *chan;
struct dma_chan *ret = NULL;
if (!__dma_device_satisfies_mask(dev, mask)) {
pr_debug("%s: wrong capabilities\n", __func__);
return NULL;
}
/* devices with multiple channels need special handling as we need to
* ensure that all channels are either private or public.
*/
if (dev->chancnt > 1 && !dma_has_cap(DMA_PRIVATE, dev->cap_mask))
list_for_each_entry(chan, &dev->channels, device_node) {
/* some channels are already publicly allocated */
if (chan->client_count)
return NULL;
}
list_for_each_entry(chan, &dev->channels, device_node) {
if (chan->client_count) {
pr_debug("%s: %s busy\n",
__func__, dev_name(&chan->dev));
continue;
}
ret = chan;
break;
}
return ret;
}
/**
* dma_request_channel - try to allocate an exclusive channel
* @mask: capabilities that the channel must satisfy
* @fn: optional callback to disposition available channels
* @fn_param: opaque parameter to pass to dma_filter_fn
*/
struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param)
{
struct dma_device *device, *_d;
struct dma_chan *chan = NULL;
enum dma_state_client ack;
int err;
/* Find a channel */
mutex_lock(&dma_list_mutex);
list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {
chan = private_candidate(mask, device);
if (!chan)
continue;
if (fn)
ack = fn(chan, fn_param);
else
ack = DMA_ACK;
if (ack == DMA_ACK) {
/* Found a suitable channel, try to grab, prep, and
* return it. We first set DMA_PRIVATE to disable
* balance_ref_count as this channel will not be
* published in the general-purpose allocator
*/
dma_cap_set(DMA_PRIVATE, device->cap_mask);
err = dma_chan_get(chan);
if (err == -ENODEV) {
pr_debug("%s: %s module removed\n", __func__,
dev_name(&chan->dev));
list_del_rcu(&device->global_node);
} else if (err)
pr_err("dmaengine: failed to get %s: (%d)\n",
dev_name(&chan->dev), err);
else
break;
} else if (ack == DMA_DUP) {
pr_debug("%s: %s filter said DMA_DUP\n",
__func__, dev_name(&chan->dev));
} else if (ack == DMA_NAK) {
pr_debug("%s: %s filter said DMA_NAK\n",
__func__, dev_name(&chan->dev));
break;
} else
WARN_ONCE(1, "filter_fn: unknown response?\n");
chan = NULL;
}
mutex_unlock(&dma_list_mutex);
pr_debug("%s: %s (%s)\n", __func__, chan ? "success" : "fail",
chan ? dev_name(&chan->dev) : NULL);
return chan;
}
EXPORT_SYMBOL_GPL(__dma_request_channel);
void dma_release_channel(struct dma_chan *chan)
{
mutex_lock(&dma_list_mutex);
WARN_ONCE(chan->client_count != 1,
"chan reference count %d != 1\n", chan->client_count);
dma_chan_put(chan);
mutex_unlock(&dma_list_mutex);
}
EXPORT_SYMBOL_GPL(dma_release_channel);
/**
* dma_chans_notify_available - broadcast available channels to the clients
*/
@ -506,7 +621,9 @@ void dma_async_client_register(struct dma_client *client)
dmaengine_ref_count++;
/* try to grab channels */
list_for_each_entry_safe(device, _d, &dma_device_list, global_node)
list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {
if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
continue;
list_for_each_entry(chan, &device->channels, device_node) {
err = dma_chan_get(chan);
if (err == -ENODEV) {
@ -517,6 +634,7 @@ void dma_async_client_register(struct dma_client *client)
pr_err("dmaengine: failed to get %s: (%d)\n",
dev_name(&chan->dev), err);
}
}
/* if this is the first reference and there were channels
* waiting we need to rebalance to get those channels
@ -547,9 +665,12 @@ void dma_async_client_unregister(struct dma_client *client)
dmaengine_ref_count--;
BUG_ON(dmaengine_ref_count < 0);
/* drop channel references */
list_for_each_entry(device, &dma_device_list, global_node)
list_for_each_entry(device, &dma_device_list, global_node) {
if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
continue;
list_for_each_entry(chan, &device->channels, device_node)
dma_chan_put(chan);
}
list_del(&client->global_node);
mutex_unlock(&dma_list_mutex);
@ -639,9 +760,11 @@ int dma_async_device_register(struct dma_device *device)
chan->slow_ref = 0;
INIT_RCU_HEAD(&chan->rcu);
}
device->chancnt = chancnt;
mutex_lock(&dma_list_mutex);
if (dmaengine_ref_count)
/* take references on public channels */
if (dmaengine_ref_count && !dma_has_cap(DMA_PRIVATE, device->cap_mask))
list_for_each_entry(chan, &device->channels, device_node) {
/* if clients are already waiting for channels we need
* to take references on their behalf

16
include/linux/dmaengine.h
View File

@ -89,6 +89,7 @@ enum dma_transaction_type {
DMA_MEMSET,
DMA_MEMCPY_CRC32C,
DMA_INTERRUPT,
DMA_PRIVATE,
DMA_SLAVE,
};
@ -223,6 +224,18 @@ struct dma_client;
typedef enum dma_state_client (*dma_event_callback) (struct dma_client *client,
struct dma_chan *chan, enum dma_state state);
/**
* typedef dma_filter_fn - callback filter for dma_request_channel
* @chan: channel to be reviewed
* @filter_param: opaque parameter passed through dma_request_channel
*
* When this optional parameter is specified in a call to dma_request_channel a
* suitable channel is passed to this routine for further dispositioning before
* being returned. Where 'suitable' indicates a non-busy channel that
* satisfies the given capability mask.
*/
typedef enum dma_state_client (*dma_filter_fn)(struct dma_chan *chan, void *filter_param);
/**
* struct dma_client - info on the entity making use of DMA services
* @event_callback: func ptr to call when something happens
@ -472,6 +485,9 @@ void dma_async_device_unregister(struct dma_device *device);
void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);
void dma_issue_pending_all(void);
#define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param);
void dma_release_channel(struct dma_chan *chan);
/* --- Helper iov-locking functions --- */