diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/dma/dmaengine.c | 168 |
1 files changed, 167 insertions, 1 deletions
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index d4d925912c4..87a8cd4791e 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -295,6 +295,164 @@ static void dma_chan_release(struct dma_chan *chan) } /** + * dma_cap_mask_all - enable iteration over all operation types + */ +static dma_cap_mask_t dma_cap_mask_all; + +/** + * dma_chan_tbl_ent - tracks channel allocations per core/operation + * @chan - associated channel for this entry + */ +struct dma_chan_tbl_ent { + struct dma_chan *chan; +}; + +/** + * channel_table - percpu lookup table for memory-to-memory offload providers + */ +static struct dma_chan_tbl_ent *channel_table[DMA_TX_TYPE_END]; + +static int __init dma_channel_table_init(void) +{ + enum dma_transaction_type cap; + int err = 0; + + bitmap_fill(dma_cap_mask_all.bits, DMA_TX_TYPE_END); + + /* 'interrupt' and 'slave' are channel capabilities, but are not + * associated with an operation so they do not need an entry in the + * channel_table + */ + clear_bit(DMA_INTERRUPT, dma_cap_mask_all.bits); + clear_bit(DMA_SLAVE, dma_cap_mask_all.bits); + + for_each_dma_cap_mask(cap, dma_cap_mask_all) { + channel_table[cap] = alloc_percpu(struct dma_chan_tbl_ent); + if (!channel_table[cap]) { + err = -ENOMEM; + break; + } + } + + if (err) { + pr_err("dmaengine: initialization failure\n"); + for_each_dma_cap_mask(cap, dma_cap_mask_all) + if (channel_table[cap]) + free_percpu(channel_table[cap]); + } + + return err; +} +subsys_initcall(dma_channel_table_init); + +/** + * dma_find_channel - find a channel to carry out the operation + * @tx_type: transaction type + */ +struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type) +{ + struct dma_chan *chan; + int cpu; + + WARN_ONCE(dmaengine_ref_count == 0, + "client called %s without a reference", __func__); + + cpu = get_cpu(); + chan = per_cpu_ptr(channel_table[tx_type], cpu)->chan; + put_cpu(); + + return chan; +} +EXPORT_SYMBOL(dma_find_channel); + +/** + * nth_chan - returns the nth channel of the given capability + * @cap: capability to match + * @n: nth channel desired + * + * Defaults to returning the channel with the desired capability and the + * lowest reference count when 'n' cannot be satisfied. Must be called + * under dma_list_mutex. + */ +static struct dma_chan *nth_chan(enum dma_transaction_type cap, int n) +{ + struct dma_device *device; + struct dma_chan *chan; + struct dma_chan *ret = NULL; + struct dma_chan *min = NULL; + + list_for_each_entry(device, &dma_device_list, global_node) { + if (!dma_has_cap(cap, device->cap_mask)) + continue; + list_for_each_entry(chan, &device->channels, device_node) { + if (!chan->client_count) + continue; + if (!min) + min = chan; + else if (chan->table_count < min->table_count) + min = chan; + + if (n-- == 0) { + ret = chan; + break; /* done */ + } + } + if (ret) + break; /* done */ + } + + if (!ret) + ret = min; + + if (ret) + ret->table_count++; + + return ret; +} + +/** + * dma_channel_rebalance - redistribute the available channels + * + * Optimize for cpu isolation (each cpu gets a dedicated channel for an + * operation type) in the SMP case, and operation isolation (avoid + * multi-tasking channels) in the non-SMP case. Must be called under + * dma_list_mutex. + */ +static void dma_channel_rebalance(void) +{ + struct dma_chan *chan; + struct dma_device *device; + int cpu; + int cap; + int n; + + /* undo the last distribution */ + for_each_dma_cap_mask(cap, dma_cap_mask_all) + for_each_possible_cpu(cpu) + per_cpu_ptr(channel_table[cap], cpu)->chan = NULL; + + list_for_each_entry(device, &dma_device_list, global_node) + list_for_each_entry(chan, &device->channels, device_node) + chan->table_count = 0; + + /* don't populate the channel_table if no clients are available */ + if (!dmaengine_ref_count) + return; + + /* redistribute available channels */ + n = 0; + for_each_dma_cap_mask(cap, dma_cap_mask_all) + for_each_online_cpu(cpu) { + if (num_possible_cpus() > 1) + chan = nth_chan(cap, n++); + else + chan = nth_chan(cap, -1); + + per_cpu_ptr(channel_table[cap], cpu)->chan = chan; + } +} + +/** * dma_chans_notify_available - broadcast available channels to the clients */ static void dma_clients_notify_available(void) @@ -339,7 +497,12 @@ void dma_async_client_register(struct dma_client *client) dev_name(&chan->dev), err); } - + /* if this is the first reference and there were channels + * waiting we need to rebalance to get those channels + * incorporated into the channel table + */ + if (dmaengine_ref_count == 1) + dma_channel_rebalance(); list_add_tail(&client->global_node, &dma_client_list); mutex_unlock(&dma_list_mutex); } @@ -473,6 +636,7 @@ int dma_async_device_register(struct dma_device *device) } } list_add_tail(&device->global_node, &dma_device_list); + dma_channel_rebalance(); mutex_unlock(&dma_list_mutex); dma_clients_notify_available(); @@ -514,6 +678,7 @@ void dma_async_device_unregister(struct dma_device *device) mutex_lock(&dma_list_mutex); list_del(&device->global_node); + dma_channel_rebalance(); mutex_unlock(&dma_list_mutex); list_for_each_entry(chan, &device->channels, device_node) { @@ -768,3 +933,4 @@ static int __init dma_bus_init(void) } subsys_initcall(dma_bus_init); + |