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dmaengine: make clients responsible for managing channels

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The current implementation assumes that a channel will only be used by one
client at a time.  In order to enable channel sharing the dmaengine core is
changed to a model where clients subscribe to channel-available-events.
Instead of tracking how many channels a client wants and how many it has
received the core just broadcasts the available channels and lets the
clients optionally take a reference.  The core learns about the clients'
needs at dma_event_callback time.

In support of multiple operation types, clients can specify a capability
mask to only be notified of channels that satisfy a certain set of
capabilities.

Changelog:
* removed DMA_TX_ARRAY_INIT, no longer needed
* dma_client_chan_free -> dma_chan_release: switch to global reference
  counting only at device unregistration time, before it was also happening
  at client unregistration time
* clients now return dma_state_client to dmaengine (ack, dup, nak)
* checkpatch.pl fixes
* fixup merge with git-ioat

Cc: Chris Leech <christopher.leech@intel.com>
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Dan Williams
2007-07-09 11:56:42 -07:00
parent 7405f74bad
commit d379b01e90
5 changed files with 224 additions and 167 deletions
Download Patch File Download Diff File Expand all files Collapse all files

110
net/core/dev.c
View File

@@ -151,9 +151,22 @@ static struct list_head ptype_base[16] __read_mostly; /* 16 way hashed list */
static struct list_head ptype_all __read_mostly; /* Taps */
#ifdef CONFIG_NET_DMA
static struct dma_client *net_dma_client;
static unsigned int net_dma_count;
static spinlock_t net_dma_event_lock;
struct net_dma {
struct dma_client client;
spinlock_t lock;
cpumask_t channel_mask;
struct dma_chan *channels[NR_CPUS];
};
static enum dma_state_client
netdev_dma_event(struct dma_client *client, struct dma_chan *chan,
enum dma_state state);
static struct net_dma net_dma = {
.client = {
.event_callback = netdev_dma_event,
},
};
#endif
/*
@@ -2015,12 +2028,13 @@ out:
* There may not be any more sk_buffs coming right now, so push
* any pending DMA copies to hardware
*/
if (net_dma_client) {
struct dma_chan *chan;
rcu_read_lock();
list_for_each_entry_rcu(chan, &net_dma_client->channels, client_node)
dma_async_memcpy_issue_pending(chan);
rcu_read_unlock();
if (!cpus_empty(net_dma.channel_mask)) {
int chan_idx;
for_each_cpu_mask(chan_idx, net_dma.channel_mask) {
struct dma_chan *chan = net_dma.channels[chan_idx];
if (chan)
dma_async_memcpy_issue_pending(chan);
}
}
#endif
return;
@@ -3563,12 +3577,13 @@ static int dev_cpu_callback(struct notifier_block *nfb,
* This is called when the number of channels allocated to the net_dma_client
* changes. The net_dma_client tries to have one DMA channel per CPU.
*/
static void net_dma_rebalance(void)
static void net_dma_rebalance(struct net_dma *net_dma)
{
unsigned int cpu, i, n;
unsigned int cpu, i, n, chan_idx;
struct dma_chan *chan;
if (net_dma_count == 0) {
if (cpus_empty(net_dma->channel_mask)) {
for_each_online_cpu(cpu)
rcu_assign_pointer(per_cpu(softnet_data, cpu).net_dma, NULL);
return;
@@ -3577,10 +3592,12 @@ static void net_dma_rebalance(void)
i = 0;
cpu = first_cpu(cpu_online_map);
rcu_read_lock();
list_for_each_entry(chan, &net_dma_client->channels, client_node) {
n = ((num_online_cpus() / net_dma_count)
+ (i < (num_online_cpus() % net_dma_count) ? 1 : 0));
for_each_cpu_mask(chan_idx, net_dma->channel_mask) {
chan = net_dma->channels[chan_idx];
n = ((num_online_cpus() / cpus_weight(net_dma->channel_mask))
+ (i < (num_online_cpus() %
cpus_weight(net_dma->channel_mask)) ? 1 : 0));
while(n) {
per_cpu(softnet_data, cpu).net_dma = chan;
@@ -3589,7 +3606,6 @@ static void net_dma_rebalance(void)
}
i++;
}
rcu_read_unlock();
}
/**
@@ -3598,23 +3614,53 @@ static void net_dma_rebalance(void)
* @chan: DMA channel for the event
* @event: event type
*/
static void netdev_dma_event(struct dma_client *client, struct dma_chan *chan,
enum dma_event event)
static enum dma_state_client
netdev_dma_event(struct dma_client *client, struct dma_chan *chan,
enum dma_state state)
{
spin_lock(&net_dma_event_lock);
switch (event) {
case DMA_RESOURCE_ADDED:
net_dma_count++;
net_dma_rebalance();
int i, found = 0, pos = -1;
struct net_dma *net_dma =
container_of(client, struct net_dma, client);
enum dma_state_client ack = DMA_DUP; /* default: take no action */
spin_lock(&net_dma->lock);
switch (state) {
case DMA_RESOURCE_AVAILABLE:
for (i = 0; i < NR_CPUS; i++)
if (net_dma->channels[i] == chan) {
found = 1;
break;
} else if (net_dma->channels[i] == NULL && pos < 0)
pos = i;
if (!found && pos >= 0) {
ack = DMA_ACK;
net_dma->channels[pos] = chan;
cpu_set(pos, net_dma->channel_mask);
net_dma_rebalance(net_dma);
}
break;
case DMA_RESOURCE_REMOVED:
net_dma_count--;
net_dma_rebalance();
for (i = 0; i < NR_CPUS; i++)
if (net_dma->channels[i] == chan) {
found = 1;
pos = i;
break;
}
if (found) {
ack = DMA_ACK;
cpu_clear(pos, net_dma->channel_mask);
net_dma->channels[i] = NULL;
net_dma_rebalance(net_dma);
}
break;
default:
break;
}
spin_unlock(&net_dma_event_lock);
spin_unlock(&net_dma->lock);
return ack;
}
/**
@@ -3622,12 +3668,10 @@ static void netdev_dma_event(struct dma_client *client, struct dma_chan *chan,
*/
static int __init netdev_dma_register(void)
{
spin_lock_init(&net_dma_event_lock);
net_dma_client = dma_async_client_register(netdev_dma_event);
if (net_dma_client == NULL)
return -ENOMEM;
dma_async_client_chan_request(net_dma_client, num_online_cpus());
spin_lock_init(&net_dma.lock);
dma_cap_set(DMA_MEMCPY, net_dma.client.cap_mask);
dma_async_client_register(&net_dma.client);
dma_async_client_chan_request(&net_dma.client);
return 0;
}