dmaengine: make clients responsible for managing channels
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>
diff --git a/net/core/dev.c b/net/core/dev.c
index ee051bb..835202f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -151,9 +151,22 @@
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 @@
* 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 @@
* 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 @@
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 @@
}
i++;
}
- rcu_read_unlock();
}
/**
@@ -3598,23 +3614,53 @@
* @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 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;
}