* Each device has a channels list, which runs unlocked but is never modified
* once the device is registered, it's just setup by the driver.
*
- * Each client has a channels list, it's only modified under the client->lock
- * and in an RCU callback, so it's safe to read under rcu_read_lock().
+ * Each client is responsible for keeping track of the channels it uses. See
+ * the definition of dma_event_callback in dmaengine.h.
*
* Each device has a kref, which is initialized to 1 when the device is
- * registered. A kref_put is done for each class_device registered. When the
+ * registered. A kref_get is done for each class_device registered. When the
* class_device is released, the coresponding kref_put is done in the release
* method. Every time one of the device's channels is allocated to a client,
* a kref_get occurs. When the channel is freed, the coresponding kref_put
* references to finish.
*
* Each channel has an open-coded implementation of Rusty Russell's "bigref,"
- * with a kref and a per_cpu local_t. A single reference is set when on an
- * ADDED event, and removed with a REMOVE event. Net DMA client takes an
- * extra reference per outstanding transaction. The relase function does a
- * kref_put on the device. -ChrisL
+ * with a kref and a per_cpu local_t. A dma_chan_get is called when a client
+ * signals that it wants to use a channel, and dma_chan_put is called when
+ * a channel is removed or a client using it is unregesitered. A client can
+ * take extra references per outstanding transaction, as is the case with
+ * the NET DMA client. The release function does a kref_put on the device.
+ * -ChrisL, DanW
*/
#include <linux/init.h>
static ssize_t show_in_use(struct class_device *cd, char *buf)
{
struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
+ int in_use = 0;
+
+ if (unlikely(chan->slow_ref) &&
+ atomic_read(&chan->refcount.refcount) > 1)
+ in_use = 1;
+ else {
+ if (local_read(&(per_cpu_ptr(chan->local,
+ get_cpu())->refcount)) > 0)
+ in_use = 1;
+ put_cpu();
+ }
- return sprintf(buf, "%d\n", (chan->client ? 1 : 0));
+ return sprintf(buf, "%d\n", in_use);
}
static struct class_device_attribute dma_class_attrs[] = {
/* --- client and device registration --- */
+#define dma_chan_satisfies_mask(chan, mask) \
+ __dma_chan_satisfies_mask((chan), &(mask))
+static int
+__dma_chan_satisfies_mask(struct dma_chan *chan, dma_cap_mask_t *want)
+{
+ dma_cap_mask_t has;
+
+ bitmap_and(has.bits, want->bits, chan->device->cap_mask.bits,
+ DMA_TX_TYPE_END);
+ return bitmap_equal(want->bits, has.bits, DMA_TX_TYPE_END);
+}
+
/**
- * dma_client_chan_alloc - try to allocate a channel to a client
+ * dma_client_chan_alloc - try to allocate channels to a client
* @client: &dma_client
*
* Called with dma_list_mutex held.
*/
-static struct dma_chan *dma_client_chan_alloc(struct dma_client *client)
+static void dma_client_chan_alloc(struct dma_client *client)
{
struct dma_device *device;
struct dma_chan *chan;
- unsigned long flags;
int desc; /* allocated descriptor count */
+ enum dma_state_client ack;
- /* Find a channel, any DMA engine will do */
- list_for_each_entry(device, &dma_device_list, global_node) {
+ /* Find a channel */
+ list_for_each_entry(device, &dma_device_list, global_node)
list_for_each_entry(chan, &device->channels, device_node) {
- if (chan->client)
+ if (!dma_chan_satisfies_mask(chan, client->cap_mask))
continue;
desc = chan->device->device_alloc_chan_resources(chan);
if (desc >= 0) {
- kref_get(&device->refcount);
- kref_init(&chan->refcount);
- chan->slow_ref = 0;
- INIT_RCU_HEAD(&chan->rcu);
- chan->client = client;
- spin_lock_irqsave(&client->lock, flags);
- list_add_tail_rcu(&chan->client_node,
- &client->channels);
- spin_unlock_irqrestore(&client->lock, flags);
- return chan;
+ ack = client->event_callback(client,
+ chan,
+ DMA_RESOURCE_AVAILABLE);
+
+ /* we are done once this client rejects
+ * an available resource
+ */
+ if (ack == DMA_ACK) {
+ dma_chan_get(chan);
+ kref_get(&device->refcount);
+ } else if (ack == DMA_NAK)
+ return;
}
}
- }
-
- return NULL;
}
enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie)
{
struct dma_chan *chan = container_of(kref, struct dma_chan, refcount);
chan->device->device_free_chan_resources(chan);
- chan->client = NULL;
kref_put(&chan->device->refcount, dma_async_device_cleanup);
}
EXPORT_SYMBOL(dma_chan_cleanup);
kref_put(&chan->refcount, dma_chan_cleanup);
}
-static void dma_client_chan_free(struct dma_chan *chan)
+static void dma_chan_release(struct dma_chan *chan)
{
atomic_add(0x7FFFFFFF, &chan->refcount.refcount);
chan->slow_ref = 1;
}
/**
- * dma_chans_rebalance - reallocate channels to clients
- *
- * When the number of DMA channel in the system changes,
- * channels need to be rebalanced among clients.
+ * dma_chans_notify_available - broadcast available channels to the clients
*/
-static void dma_chans_rebalance(void)
+static void dma_clients_notify_available(void)
{
struct dma_client *client;
- struct dma_chan *chan;
- unsigned long flags;
mutex_lock(&dma_list_mutex);
- list_for_each_entry(client, &dma_client_list, global_node) {
- while (client->chans_desired > client->chan_count) {
- chan = dma_client_chan_alloc(client);
- if (!chan)
- break;
- client->chan_count++;
- client->event_callback(client,
- chan,
- DMA_RESOURCE_ADDED);
- }
- while (client->chans_desired < client->chan_count) {
- spin_lock_irqsave(&client->lock, flags);
- chan = list_entry(client->channels.next,
- struct dma_chan,
- client_node);
- list_del_rcu(&chan->client_node);
- spin_unlock_irqrestore(&client->lock, flags);
- client->chan_count--;
- client->event_callback(client,
- chan,
- DMA_RESOURCE_REMOVED);
- dma_client_chan_free(chan);
- }
- }
+ list_for_each_entry(client, &dma_client_list, global_node)
+ dma_client_chan_alloc(client);
mutex_unlock(&dma_list_mutex);
}
/**
- * dma_async_client_register - allocate and register a &dma_client
- * @event_callback: callback for notification of channel addition/removal
+ * dma_chans_notify_available - tell the clients that a channel is going away
+ * @chan: channel on its way out
*/
-struct dma_client *dma_async_client_register(dma_event_callback event_callback)
+static void dma_clients_notify_removed(struct dma_chan *chan)
{
struct dma_client *client;
+ enum dma_state_client ack;
- client = kzalloc(sizeof(*client), GFP_KERNEL);
- if (!client)
- return NULL;
+ mutex_lock(&dma_list_mutex);
+
+ list_for_each_entry(client, &dma_client_list, global_node) {
+ ack = client->event_callback(client, chan,
+ DMA_RESOURCE_REMOVED);
+
+ /* client was holding resources for this channel so
+ * free it
+ */
+ if (ack == DMA_ACK) {
+ dma_chan_put(chan);
+ kref_put(&chan->device->refcount,
+ dma_async_device_cleanup);
+ }
+ }
- INIT_LIST_HEAD(&client->channels);
- spin_lock_init(&client->lock);
- client->chans_desired = 0;
- client->chan_count = 0;
- client->event_callback = event_callback;
+ mutex_unlock(&dma_list_mutex);
+}
+/**
+ * dma_async_client_register - register a &dma_client
+ * @client: ptr to a client structure with valid 'event_callback' and 'cap_mask'
+ */
+void dma_async_client_register(struct dma_client *client)
+{
mutex_lock(&dma_list_mutex);
list_add_tail(&client->global_node, &dma_client_list);
mutex_unlock(&dma_list_mutex);
-
- return client;
}
EXPORT_SYMBOL(dma_async_client_register);
*/
void dma_async_client_unregister(struct dma_client *client)
{
+ struct dma_device *device;
struct dma_chan *chan;
+ enum dma_state_client ack;
if (!client)
return;
- rcu_read_lock();
- list_for_each_entry_rcu(chan, &client->channels, client_node)
- dma_client_chan_free(chan);
- rcu_read_unlock();
-
mutex_lock(&dma_list_mutex);
+ /* free all channels the client is holding */
+ list_for_each_entry(device, &dma_device_list, global_node)
+ list_for_each_entry(chan, &device->channels, device_node) {
+ ack = client->event_callback(client, chan,
+ DMA_RESOURCE_REMOVED);
+
+ if (ack == DMA_ACK) {
+ dma_chan_put(chan);
+ kref_put(&chan->device->refcount,
+ dma_async_device_cleanup);
+ }
+ }
+
list_del(&client->global_node);
mutex_unlock(&dma_list_mutex);
-
- kfree(client);
- dma_chans_rebalance();
}
EXPORT_SYMBOL(dma_async_client_unregister);
/**
- * dma_async_client_chan_request - request DMA channels
- * @client: &dma_client
- * @number: count of DMA channels requested
- *
- * Clients call dma_async_client_chan_request() to specify how many
- * DMA channels they need, 0 to free all currently allocated.
- * The resulting allocations/frees are indicated to the client via the
- * event callback.
+ * dma_async_client_chan_request - send all available channels to the
+ * client that satisfy the capability mask
+ * @client - requester
*/
-void dma_async_client_chan_request(struct dma_client *client,
- unsigned int number)
+void dma_async_client_chan_request(struct dma_client *client)
{
- client->chans_desired = number;
- dma_chans_rebalance();
+ mutex_lock(&dma_list_mutex);
+ dma_client_chan_alloc(client);
+ mutex_unlock(&dma_list_mutex);
}
EXPORT_SYMBOL(dma_async_client_chan_request);
}
kref_get(&device->refcount);
+ kref_init(&chan->refcount);
+ chan->slow_ref = 0;
+ INIT_RCU_HEAD(&chan->rcu);
}
mutex_lock(&dma_list_mutex);
list_add_tail(&device->global_node, &dma_device_list);
mutex_unlock(&dma_list_mutex);
- dma_chans_rebalance();
+ dma_clients_notify_available();
return 0;
void dma_async_device_unregister(struct dma_device *device)
{
struct dma_chan *chan;
- unsigned long flags;
mutex_lock(&dma_list_mutex);
list_del(&device->global_node);
mutex_unlock(&dma_list_mutex);
list_for_each_entry(chan, &device->channels, device_node) {
- if (chan->client) {
- spin_lock_irqsave(&chan->client->lock, flags);
- list_del(&chan->client_node);
- chan->client->chan_count--;
- spin_unlock_irqrestore(&chan->client->lock, flags);
- chan->client->event_callback(chan->client,
- chan,
- DMA_RESOURCE_REMOVED);
- dma_client_chan_free(chan);
- }
+ dma_clients_notify_removed(chan);
class_device_unregister(&chan->class_dev);
+ dma_chan_release(chan);
}
- dma_chans_rebalance();
kref_put(&device->refcount, dma_async_device_cleanup);
wait_for_completion(&device->done);
#include <linux/dma-mapping.h>
/**
- * enum dma_event - resource PNP/power managment events
+ * enum dma_state - resource PNP/power managment state
* @DMA_RESOURCE_SUSPEND: DMA device going into low power state
* @DMA_RESOURCE_RESUME: DMA device returning to full power
- * @DMA_RESOURCE_ADDED: DMA device added to the system
+ * @DMA_RESOURCE_AVAILABLE: DMA device available to the system
* @DMA_RESOURCE_REMOVED: DMA device removed from the system
*/
-enum dma_event {
+enum dma_state {
DMA_RESOURCE_SUSPEND,
DMA_RESOURCE_RESUME,
- DMA_RESOURCE_ADDED,
+ DMA_RESOURCE_AVAILABLE,
DMA_RESOURCE_REMOVED,
};
+/**
+ * enum dma_state_client - state of the channel in the client
+ * @DMA_ACK: client would like to use, or was using this channel
+ * @DMA_DUP: client has already seen this channel, or is not using this channel
+ * @DMA_NAK: client does not want to see any more channels
+ */
+enum dma_state_client {
+ DMA_ACK,
+ DMA_DUP,
+ DMA_NAK,
+};
+
/**
* typedef dma_cookie_t - an opaque DMA cookie
*
/**
* struct dma_chan - devices supply DMA channels, clients use them
- * @client: ptr to the client user of this chan, will be %NULL when unused
* @device: ptr to the dma device who supplies this channel, always !%NULL
* @cookie: last cookie value returned to client
* @chan_id: channel ID for sysfs
* @refcount: kref, used in "bigref" slow-mode
* @slow_ref: indicates that the DMA channel is free
* @rcu: the DMA channel's RCU head
- * @client_node: used to add this to the client chan list
* @device_node: used to add this to the device chan list
* @local: per-cpu pointer to a struct dma_chan_percpu
*/
struct dma_chan {
- struct dma_client *client;
struct dma_device *device;
dma_cookie_t cookie;
int slow_ref;
struct rcu_head rcu;
- struct list_head client_node;
struct list_head device_node;
struct dma_chan_percpu *local;
};
+
void dma_chan_cleanup(struct kref *kref);
static inline void dma_chan_get(struct dma_chan *chan)
/*
* typedef dma_event_callback - function pointer to a DMA event callback
+ * For each channel added to the system this routine is called for each client.
+ * If the client would like to use the channel it returns '1' to signal (ack)
+ * the dmaengine core to take out a reference on the channel and its
+ * corresponding device. A client must not 'ack' an available channel more
+ * than once. When a channel is removed all clients are notified. If a client
+ * is using the channel it must 'ack' the removal. A client must not 'ack' a
+ * removed channel more than once.
+ * @client - 'this' pointer for the client context
+ * @chan - channel to be acted upon
+ * @state - available or removed
*/
-typedef void (*dma_event_callback) (struct dma_client *client,
- struct dma_chan *chan, enum dma_event event);
+struct dma_client;
+typedef enum dma_state_client (*dma_event_callback) (struct dma_client *client,
+ struct dma_chan *chan, enum dma_state state);
/**
* struct dma_client - info on the entity making use of DMA services
* @event_callback: func ptr to call when something happens
- * @chan_count: number of chans allocated
- * @chans_desired: number of chans requested. Can be +/- chan_count
- * @lock: protects access to the channels list
- * @channels: the list of DMA channels allocated
+ * @cap_mask: only return channels that satisfy the requested capabilities
+ * a value of zero corresponds to any capability
* @global_node: list_head for global dma_client_list
*/
struct dma_client {
dma_event_callback event_callback;
- unsigned int chan_count;
- unsigned int chans_desired;
-
- spinlock_t lock;
- struct list_head channels;
+ dma_cap_mask_t cap_mask;
struct list_head global_node;
};
/* --- public DMA engine API --- */
-struct dma_client *dma_async_client_register(dma_event_callback event_callback);
+void dma_async_client_register(struct dma_client *client);
void dma_async_client_unregister(struct dma_client *client);
-void dma_async_client_chan_request(struct dma_client *client,
- unsigned int number);
+void dma_async_client_chan_request(struct dma_client *client);
dma_cookie_t dma_async_memcpy_buf_to_buf(struct dma_chan *chan,
void *dest, void *src, size_t len);
dma_cookie_t dma_async_memcpy_buf_to_pg(struct dma_chan *chan,
void dma_async_tx_descriptor_init(struct dma_async_tx_descriptor *tx,
struct dma_chan *chan);
-
static inline void
async_tx_ack(struct dma_async_tx_descriptor *tx)
{
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
/*
* 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;
* 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;
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;
}
i++;
}
- rcu_read_unlock();
}
/**
* @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)
-{
- spin_lock(&net_dma_event_lock);
- switch (event) {
- case DMA_RESOURCE_ADDED:
- net_dma_count++;
- net_dma_rebalance();
+static enum dma_state_client
+netdev_dma_event(struct dma_client *client, struct dma_chan *chan,
+ enum dma_state state)
+{
+ 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;
}
/**
*/
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;
}
projects / linux-2.6 / commitdiff