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DEFINITIONS
This source file includes following definitions.
- async_tx_issue_pending_all
- dma_wait_for_async_tx
- async_tx_run_dependencies
- free_dma_chan_ref
- init_dma_chan_ref
- get_chan_ref_by_cap
- async_tx_rebalance
- dma_channel_add_remove
- async_tx_init
- async_tx_exit
- __async_tx_find_channel
- async_tx_init
- async_tx_exit
- async_tx_channel_switch
- async_tx_submit
- async_trigger_callback
- async_tx_quiesce
/*
* core routines for the asynchronous memory transfer/transform api
*
* Copyright © 2006, Intel Corporation.
*
* Dan Williams <dan.j.williams@intel.com>
*
* with architecture considerations by:
* Neil Brown <neilb@suse.de>
* Jeff Garzik <jeff@garzik.org>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
*
*/
#include <linux/rculist.h>
#include <linux/kernel.h>
#include <linux/async_tx.h>
#ifdef CONFIG_DMA_ENGINE
static enum dma_state_client
dma_channel_add_remove(struct dma_client *client,
struct dma_chan *chan, enum dma_state state);
static struct dma_client async_tx_dma = {
.event_callback = dma_channel_add_remove,
/* .cap_mask == 0 defaults to all channels */
};
/**
* dma_cap_mask_all - enable iteration over all operation types
*/
static dma_cap_mask_t dma_cap_mask_all;
/**
* chan_ref_percpu - tracks channel allocations per core/opertion
*/
struct chan_ref_percpu {
struct dma_chan_ref *ref;
};
static int channel_table_initialized;
static struct chan_ref_percpu *channel_table[DMA_TX_TYPE_END];
/**
* async_tx_lock - protect modification of async_tx_master_list and serialize
* rebalance operations
*/
static spinlock_t async_tx_lock;
static LIST_HEAD(async_tx_master_list);
/* async_tx_issue_pending_all - start all transactions on all channels */
void async_tx_issue_pending_all(void)
{
struct dma_chan_ref *ref;
rcu_read_lock();
list_for_each_entry_rcu(ref, &async_tx_master_list, node)
ref->chan->device->device_issue_pending(ref->chan);
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(async_tx_issue_pending_all);
/* dma_wait_for_async_tx - spin wait for a transcation to complete
* @tx: transaction to wait on
*/
enum dma_status
dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
{
enum dma_status status;
struct dma_async_tx_descriptor *iter;
struct dma_async_tx_descriptor *parent;
if (!tx)
return DMA_SUCCESS;
/* poll through the dependency chain, return when tx is complete */
do {
iter = tx;
/* find the root of the unsubmitted dependency chain */
do {
parent = iter->parent;
if (!parent)
break;
else
iter = parent;
} while (parent);
/* there is a small window for ->parent == NULL and
* ->cookie == -EBUSY
*/
while (iter->cookie == -EBUSY)
cpu_relax();
status = dma_sync_wait(iter->chan, iter->cookie);
} while (status == DMA_IN_PROGRESS || (iter != tx));
return status;
}
EXPORT_SYMBOL_GPL(dma_wait_for_async_tx);
/* async_tx_run_dependencies - helper routine for dma drivers to process
* (start) dependent operations on their target channel
* @tx: transaction with dependencies
*/
void
async_tx_run_dependencies(struct dma_async_tx_descriptor *tx)
{
struct dma_async_tx_descriptor *next = tx->next;
struct dma_chan *chan;
if (!next)
return;
tx->next = NULL;
chan = next->chan;
/* keep submitting up until a channel switch is detected
* in that case we will be called again as a result of
* processing the interrupt from async_tx_channel_switch
*/
while (next && next->chan == chan) {
struct dma_async_tx_descriptor *_next;
spin_lock_bh(&next->lock);
next->parent = NULL;
_next = next->next;
if (_next && _next->chan == chan)
next->next = NULL;
spin_unlock_bh(&next->lock);
next->tx_submit(next);
next = _next;
}
chan->device->device_issue_pending(chan);
}
EXPORT_SYMBOL_GPL(async_tx_run_dependencies);
static void
free_dma_chan_ref(struct rcu_head *rcu)
{
struct dma_chan_ref *ref;
ref = container_of(rcu, struct dma_chan_ref, rcu);
kfree(ref);
}
static void
init_dma_chan_ref(struct dma_chan_ref *ref, struct dma_chan *chan)
{
INIT_LIST_HEAD(&ref->node);
INIT_RCU_HEAD(&ref->rcu);
ref->chan = chan;
atomic_set(&ref->count, 0);
}
/**
* get_chan_ref_by_cap - returns the nth channel of the given capability
* defaults to returning the channel with the desired capability and the
* lowest reference count if the index can not be satisfied
* @cap: capability to match
* @index: nth channel desired, passing -1 has the effect of forcing the
* default return value
*/
static struct dma_chan_ref *
get_chan_ref_by_cap(enum dma_transaction_type cap, int index)
{
struct dma_chan_ref *ret_ref = NULL, *min_ref = NULL, *ref;
rcu_read_lock();
list_for_each_entry_rcu(ref, &async_tx_master_list, node)
if (dma_has_cap(cap, ref->chan->device->cap_mask)) {
if (!min_ref)
min_ref = ref;
else if (atomic_read(&ref->count) <
atomic_read(&min_ref->count))
min_ref = ref;
if (index-- == 0) {
ret_ref = ref;
break;
}
}
rcu_read_unlock();
if (!ret_ref)
ret_ref = min_ref;
if (ret_ref)
atomic_inc(&ret_ref->count);
return ret_ref;
}
/**
* async_tx_rebalance - redistribute the available channels, optimize
* for cpu isolation in the SMP case, and opertaion isolation in the
* uniprocessor case
*/
static void async_tx_rebalance(void)
{
int cpu, cap, cpu_idx = 0;
unsigned long flags;
if (!channel_table_initialized)
return;
spin_lock_irqsave(&async_tx_lock, flags);
/* undo the last distribution */
for_each_dma_cap_mask(cap, dma_cap_mask_all)
for_each_possible_cpu(cpu) {
struct dma_chan_ref *ref =
per_cpu_ptr(channel_table[cap], cpu)->ref;
if (ref) {
atomic_set(&ref->count, 0);
per_cpu_ptr(channel_table[cap], cpu)->ref =
NULL;
}
}
for_each_dma_cap_mask(cap, dma_cap_mask_all)
for_each_online_cpu(cpu) {
struct dma_chan_ref *new;
if (NR_CPUS > 1)
new = get_chan_ref_by_cap(cap, cpu_idx++);
else
new = get_chan_ref_by_cap(cap, -1);
per_cpu_ptr(channel_table[cap], cpu)->ref = new;
}
spin_unlock_irqrestore(&async_tx_lock, flags);
}
static enum dma_state_client
dma_channel_add_remove(struct dma_client *client,
struct dma_chan *chan, enum dma_state state)
{
unsigned long found, flags;
struct dma_chan_ref *master_ref, *ref;
enum dma_state_client ack = DMA_DUP; /* default: take no action */
switch (state) {
case DMA_RESOURCE_AVAILABLE:
found = 0;
rcu_read_lock();
list_for_each_entry_rcu(ref, &async_tx_master_list, node)
if (ref->chan == chan) {
found = 1;
break;
}
rcu_read_unlock();
pr_debug("async_tx: dma resource available [%s]\n",
found ? "old" : "new");
if (!found)
ack = DMA_ACK;
else
break;
/* add the channel to the generic management list */
master_ref = kmalloc(sizeof(*master_ref), GFP_KERNEL);
if (master_ref) {
/* keep a reference until async_tx is unloaded */
dma_chan_get(chan);
init_dma_chan_ref(master_ref, chan);
spin_lock_irqsave(&async_tx_lock, flags);
list_add_tail_rcu(&master_ref->node,
&async_tx_master_list);
spin_unlock_irqrestore(&async_tx_lock,
flags);
} else {
printk(KERN_WARNING "async_tx: unable to create"
" new master entry in response to"
" a DMA_RESOURCE_ADDED event"
" (-ENOMEM)\n");
return 0;
}
async_tx_rebalance();
break;
case DMA_RESOURCE_REMOVED:
found = 0;
spin_lock_irqsave(&async_tx_lock, flags);
list_for_each_entry(ref, &async_tx_master_list, node)
if (ref->chan == chan) {
/* permit backing devices to go away */
dma_chan_put(ref->chan);
list_del_rcu(&ref->node);
call_rcu(&ref->rcu, free_dma_chan_ref);
found = 1;
break;
}
spin_unlock_irqrestore(&async_tx_lock, flags);
pr_debug("async_tx: dma resource removed [%s]\n",
found ? "ours" : "not ours");
if (found)
ack = DMA_ACK;
else
break;
async_tx_rebalance();
break;
case DMA_RESOURCE_SUSPEND:
case DMA_RESOURCE_RESUME:
printk(KERN_WARNING "async_tx: does not support dma channel"
" suspend/resume\n");
break;
default:
BUG();
}
return ack;
}
static int __init
async_tx_init(void)
{
enum dma_transaction_type cap;
spin_lock_init(&async_tx_lock);
bitmap_fill(dma_cap_mask_all.bits, DMA_TX_TYPE_END);
/* an interrupt will never be an explicit operation type.
* clearing this bit prevents allocation to a slot in 'channel_table'
*/
clear_bit(DMA_INTERRUPT, dma_cap_mask_all.bits);
for_each_dma_cap_mask(cap, dma_cap_mask_all) {
channel_table[cap] = alloc_percpu(struct chan_ref_percpu);
if (!channel_table[cap])
goto err;
}
channel_table_initialized = 1;
dma_async_client_register(&async_tx_dma);
dma_async_client_chan_request(&async_tx_dma);
printk(KERN_INFO "async_tx: api initialized (async)\n");
return 0;
err:
printk(KERN_ERR "async_tx: initialization failure\n");
while (--cap >= 0)
free_percpu(channel_table[cap]);
return 1;
}
static void __exit async_tx_exit(void)
{
enum dma_transaction_type cap;
channel_table_initialized = 0;
for_each_dma_cap_mask(cap, dma_cap_mask_all)
if (channel_table[cap])
free_percpu(channel_table[cap]);
dma_async_client_unregister(&async_tx_dma);
}
/**
* __async_tx_find_channel - find a channel to carry out the operation or let
* the transaction execute synchronously
* @depend_tx: transaction dependency
* @tx_type: transaction type
*/
struct dma_chan *
__async_tx_find_channel(struct dma_async_tx_descriptor *depend_tx,
enum dma_transaction_type tx_type)
{
/* see if we can keep the chain on one channel */
if (depend_tx &&
dma_has_cap(tx_type, depend_tx->chan->device->cap_mask))
return depend_tx->chan;
else if (likely(channel_table_initialized)) {
struct dma_chan_ref *ref;
int cpu = get_cpu();
ref = per_cpu_ptr(channel_table[tx_type], cpu)->ref;
put_cpu();
return ref ? ref->chan : NULL;
} else
return NULL;
}
EXPORT_SYMBOL_GPL(__async_tx_find_channel);
#else
static int __init async_tx_init(void)
{
printk(KERN_INFO "async_tx: api initialized (sync-only)\n");
return 0;
}
static void __exit async_tx_exit(void)
{
do { } while (0);
}
#endif
/**
* async_tx_channel_switch - queue an interrupt descriptor with a dependency
* pre-attached.
* @depend_tx: the operation that must finish before the new operation runs
* @tx: the new operation
*/
static void
async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
struct dma_async_tx_descriptor *tx)
{
struct dma_chan *chan;
struct dma_device *device;
struct dma_async_tx_descriptor *intr_tx = (void *) ~0;
/* first check to see if we can still append to depend_tx */
spin_lock_bh(&depend_tx->lock);
if (depend_tx->parent && depend_tx->chan == tx->chan) {
tx->parent = depend_tx;
depend_tx->next = tx;
intr_tx = NULL;
}
spin_unlock_bh(&depend_tx->lock);
if (!intr_tx)
return;
chan = depend_tx->chan;
device = chan->device;
/* see if we can schedule an interrupt
* otherwise poll for completion
*/
if (dma_has_cap(DMA_INTERRUPT, device->cap_mask))
intr_tx = device->device_prep_dma_interrupt(chan, 0);
else
intr_tx = NULL;
if (intr_tx) {
intr_tx->callback = NULL;
intr_tx->callback_param = NULL;
tx->parent = intr_tx;
/* safe to set ->next outside the lock since we know we are
* not submitted yet
*/
intr_tx->next = tx;
/* check if we need to append */
spin_lock_bh(&depend_tx->lock);
if (depend_tx->parent) {
intr_tx->parent = depend_tx;
depend_tx->next = intr_tx;
async_tx_ack(intr_tx);
intr_tx = NULL;
}
spin_unlock_bh(&depend_tx->lock);
if (intr_tx) {
intr_tx->parent = NULL;
intr_tx->tx_submit(intr_tx);
async_tx_ack(intr_tx);
}
} else {
if (dma_wait_for_async_tx(depend_tx) == DMA_ERROR)
panic("%s: DMA_ERROR waiting for depend_tx\n",
__func__);
tx->tx_submit(tx);
}
}
/**
* submit_disposition - while holding depend_tx->lock we must avoid submitting
* new operations to prevent a circular locking dependency with
* drivers that already hold a channel lock when calling
* async_tx_run_dependencies.
* @ASYNC_TX_SUBMITTED: we were able to append the new operation under the lock
* @ASYNC_TX_CHANNEL_SWITCH: when the lock is dropped schedule a channel switch
* @ASYNC_TX_DIRECT_SUBMIT: when the lock is dropped submit directly
*/
enum submit_disposition {
ASYNC_TX_SUBMITTED,
ASYNC_TX_CHANNEL_SWITCH,
ASYNC_TX_DIRECT_SUBMIT,
};
void
async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
enum async_tx_flags flags, struct dma_async_tx_descriptor *depend_tx,
dma_async_tx_callback cb_fn, void *cb_param)
{
tx->callback = cb_fn;
tx->callback_param = cb_param;
if (depend_tx) {
enum submit_disposition s;
/* sanity check the dependency chain:
* 1/ if ack is already set then we cannot be sure
* we are referring to the correct operation
* 2/ dependencies are 1:1 i.e. two transactions can
* not depend on the same parent
*/
BUG_ON(async_tx_test_ack(depend_tx) || depend_tx->next ||
tx->parent);
/* the lock prevents async_tx_run_dependencies from missing
* the setting of ->next when ->parent != NULL
*/
spin_lock_bh(&depend_tx->lock);
if (depend_tx->parent) {
/* we have a parent so we can not submit directly
* if we are staying on the same channel: append
* else: channel switch
*/
if (depend_tx->chan == chan) {
tx->parent = depend_tx;
depend_tx->next = tx;
s = ASYNC_TX_SUBMITTED;
} else
s = ASYNC_TX_CHANNEL_SWITCH;
} else {
/* we do not have a parent so we may be able to submit
* directly if we are staying on the same channel
*/
if (depend_tx->chan == chan)
s = ASYNC_TX_DIRECT_SUBMIT;
else
s = ASYNC_TX_CHANNEL_SWITCH;
}
spin_unlock_bh(&depend_tx->lock);
switch (s) {
case ASYNC_TX_SUBMITTED:
break;
case ASYNC_TX_CHANNEL_SWITCH:
async_tx_channel_switch(depend_tx, tx);
break;
case ASYNC_TX_DIRECT_SUBMIT:
tx->parent = NULL;
tx->tx_submit(tx);
break;
}
} else {
tx->parent = NULL;
tx->tx_submit(tx);
}
if (flags & ASYNC_TX_ACK)
async_tx_ack(tx);
if (depend_tx && (flags & ASYNC_TX_DEP_ACK))
async_tx_ack(depend_tx);
}
EXPORT_SYMBOL_GPL(async_tx_submit);
/**
* async_trigger_callback - schedules the callback function to be run after
* any dependent operations have been completed.
* @flags: ASYNC_TX_ACK, ASYNC_TX_DEP_ACK
* @depend_tx: 'callback' requires the completion of this transaction
* @cb_fn: function to call after depend_tx completes
* @cb_param: parameter to pass to the callback routine
*/
struct dma_async_tx_descriptor *
async_trigger_callback(enum async_tx_flags flags,
struct dma_async_tx_descriptor *depend_tx,
dma_async_tx_callback cb_fn, void *cb_param)
{
struct dma_chan *chan;
struct dma_device *device;
struct dma_async_tx_descriptor *tx;
if (depend_tx) {
chan = depend_tx->chan;
device = chan->device;
/* see if we can schedule an interrupt
* otherwise poll for completion
*/
if (device && !dma_has_cap(DMA_INTERRUPT, device->cap_mask))
device = NULL;
tx = device ? device->device_prep_dma_interrupt(chan, 0) : NULL;
} else
tx = NULL;
if (tx) {
pr_debug("%s: (async)\n", __func__);
async_tx_submit(chan, tx, flags, depend_tx, cb_fn, cb_param);
} else {
pr_debug("%s: (sync)\n", __func__);
/* wait for any prerequisite operations */
async_tx_quiesce(&depend_tx);
async_tx_sync_epilog(cb_fn, cb_param);
}
return tx;
}
EXPORT_SYMBOL_GPL(async_trigger_callback);
/**
* async_tx_quiesce - ensure tx is complete and freeable upon return
* @tx - transaction to quiesce
*/
void async_tx_quiesce(struct dma_async_tx_descriptor **tx)
{
if (*tx) {
/* if ack is already set then we cannot be sure
* we are referring to the correct operation
*/
BUG_ON(async_tx_test_ack(*tx));
if (dma_wait_for_async_tx(*tx) == DMA_ERROR)
panic("DMA_ERROR waiting for transaction\n");
async_tx_ack(*tx);
*tx = NULL;
}
}
EXPORT_SYMBOL_GPL(async_tx_quiesce);
module_init(async_tx_init);
module_exit(async_tx_exit);
MODULE_AUTHOR("Intel Corporation");
MODULE_DESCRIPTION("Asynchronous Bulk Memory Transactions API");
MODULE_LICENSE("GPL");