/* * 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/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; 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_rcu(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 */ if (depend_tx) { /* if ack is already set then we cannot be sure * we are referring to the correct operation */ BUG_ON(async_tx_test_ack(depend_tx)); if (dma_wait_for_async_tx(depend_tx) == DMA_ERROR) panic("%s: DMA_ERROR waiting for depend_tx\n", __func__); } async_tx_sync_epilog(flags, depend_tx, cb_fn, cb_param); } return tx; } EXPORT_SYMBOL_GPL(async_trigger_callback); module_init(async_tx_init); module_exit(async_tx_exit); MODULE_AUTHOR("Intel Corporation"); MODULE_DESCRIPTION("Asynchronous Bulk Memory Transactions API"); MODULE_LICENSE("GPL");