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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>
hifive-unleashed-5.1
Dan Williams 2007-07-09 11:56:42 -07:00
parent 7405f74bad
commit d379b01e90
5 changed files with 224 additions and 167 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

219
drivers/dma/dmaengine.c
View File

@ -37,11 +37,11 @@
* 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
@ -51,10 +51,12 @@
* 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>
@ -102,8 +104,19 @@ static ssize_t show_bytes_transferred(struct class_device *cd, char *buf)
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;
return sprintf(buf, "%d\n", (chan->client ? 1 : 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", in_use);
}
static struct class_device_attribute dma_class_attrs[] = {
@ -129,42 +142,53 @@ static struct class dma_devclass = {
/* --- 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)
@ -193,7 +217,6 @@ void dma_chan_cleanup(struct kref *kref)
{
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);
@ -209,7 +232,7 @@ static void dma_chan_free_rcu(struct rcu_head *rcu)
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;
@ -217,41 +240,42 @@ static void dma_client_chan_free(struct dma_chan *chan)
}
/**
* 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)
dma_client_chan_alloc(client);
mutex_unlock(&dma_list_mutex);
}
/**
* dma_chans_notify_available - tell the clients that a channel is going away
* @chan: channel on its way out
*/
static void dma_clients_notify_removed(struct dma_chan *chan)
{
struct dma_client *client;
enum dma_state_client ack;
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);
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);
}
}
@ -259,28 +283,14 @@ static void dma_chans_rebalance(void)
}
/**
* dma_async_client_register - allocate and register a &dma_client
* @event_callback: callback for notification of channel addition/removal
* dma_async_client_register - register a &dma_client
* @client: ptr to a client structure with valid 'event_callback' and 'cap_mask'
*/
struct dma_client *dma_async_client_register(dma_event_callback event_callback)
void dma_async_client_register(struct dma_client *client)
{
struct dma_client *client;
client = kzalloc(sizeof(*client), GFP_KERNEL);
if (!client)
return NULL;
INIT_LIST_HEAD(&client->channels);
spin_lock_init(&client->lock);
client->chans_desired = 0;
client->chan_count = 0;
client->event_callback = event_callback;
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);
@ -292,40 +302,42 @@ 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);
@ -386,13 +398,16 @@ int dma_async_device_register(struct dma_device *device)
}
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;
@ -428,26 +443,16 @@ static void dma_async_device_cleanup(struct kref *kref)
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);

1
drivers/dma/ioatdma.c
View File

@ -72,7 +72,6 @@ static int enumerate_dma_channels(struct ioat_device *device)
INIT_LIST_HEAD(&ioat_chan->used_desc);
/* This should be made common somewhere in dmaengine.c */
ioat_chan->common.device = &device->common;
ioat_chan->common.client = NULL;
list_add_tail(&ioat_chan->common.device_node,
&device->common.channels);
}

3
drivers/dma/ioatdma.h
View File

@ -30,9 +30,6 @@
#define IOAT_LOW_COMPLETION_MASK 0xffffffc0
extern struct list_head dma_device_list;
extern struct list_head dma_client_list;
/**
* struct ioat_device - internal representation of a IOAT device
* @pdev: PCI-Express device

58
include/linux/dmaengine.h
View File

@ -29,19 +29,31 @@
#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
*
@ -104,7 +116,6 @@ struct dma_chan_percpu {
/**
* 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
@ -112,12 +123,10 @@ struct dma_chan_percpu {
* @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;
@ -129,11 +138,11 @@ struct dma_chan {
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)
@ -158,26 +167,31 @@ static inline void dma_chan_put(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;
};
@ -285,10 +299,9 @@ struct dma_device {
/* --- 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,
@ -299,7 +312,6 @@ dma_cookie_t dma_async_memcpy_pg_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)
{

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;
}