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Commit 59b5ec21 authored by Dan Williams's avatar Dan Williams
Browse files

dmaengine: introduce dma_request_channel and private channels 



This interface is primarily for device-to-memory clients which need to
search for dma channels with platform-specific characteristics.  The
prototype is:

struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
                                     dma_filter_fn filter_fn,
                                     void *filter_param);

When the optional 'filter_fn' parameter is set to NULL
dma_request_channel simply returns the first channel that satisfies the
capability mask.  Otherwise, when the mask parameter is insufficient for
specifying the necessary channel, the filter_fn routine can be used to
disposition the available channels in the system. The filter_fn routine
is called once for each free channel in the system.  Upon seeing a
suitable channel filter_fn returns DMA_ACK which flags that channel to
be the return value from dma_request_channel.  A channel allocated via
this interface is exclusive to the caller, until dma_release_channel()
is called.

To ensure that all channels are not consumed by the general-purpose
allocator the DMA_PRIVATE capability is provided to exclude a dma_device
from general-purpose (memory-to-memory) consideration.

Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Acked-by: default avatarMaciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent f67b4599

drivers/dma/dmaengine.c

+139 −16
Original line number Diff line number Diff line
@@ -134,14 +134,14 @@ static struct class dma_devclass = { 


/* --- client and device registration --- */



#define dma_chan_satisfies_mask(chan, mask) \

	__dma_chan_satisfies_mask((chan), &(mask))

#define dma_device_satisfies_mask(device, mask) \

	__dma_device_satisfies_mask((device), &(mask))

static int

__dma_chan_satisfies_mask(struct dma_chan *chan, dma_cap_mask_t *want)

__dma_device_satisfies_mask(struct dma_device *device, dma_cap_mask_t *want)

{

	dma_cap_mask_t has;



	bitmap_and(has.bits, want->bits, chan->device->cap_mask.bits,

	bitmap_and(has.bits, want->bits, device->cap_mask.bits,

		DMA_TX_TYPE_END);

	return bitmap_equal(want->bits, has.bits, DMA_TX_TYPE_END);

}
@@ -195,7 +195,7 @@ static int dma_chan_get(struct dma_chan *chan) 
			err = desc_cnt;

			chan->client_count = 0;

			module_put(owner);

		} else

		} else if (!dma_has_cap(DMA_PRIVATE, chan->device->cap_mask))

			balance_ref_count(chan);

	}
@@ -232,14 +232,16 @@ static void dma_client_chan_alloc(struct dma_client *client) 


	/* Find a channel */

	list_for_each_entry(device, &dma_device_list, global_node) {

		if (dma_has_cap(DMA_PRIVATE, device->cap_mask))

			continue;

		/* Does the client require a specific DMA controller? */

		if (client->slave && client->slave->dma_dev

				&& client->slave->dma_dev != device->dev)

			continue;

		if (!dma_device_satisfies_mask(device, client->cap_mask))

			continue;



		list_for_each_entry(chan, &device->channels, device_node) {

			if (!dma_chan_satisfies_mask(chan, client->cap_mask))

				continue;

			if (!chan->client_count)

				continue;

			ack = client->event_callback(client, chan,
@@ -320,11 +322,12 @@ static int __init dma_channel_table_init(void) 


	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

	/* 'interrupt', 'private', 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_PRIVATE, dma_cap_mask_all.bits);

	clear_bit(DMA_SLAVE, dma_cap_mask_all.bits);



	for_each_dma_cap_mask(cap, dma_cap_mask_all) {
@@ -378,10 +381,13 @@ void dma_issue_pending_all(void) 
		  "client called %s without a reference", __func__);



	rcu_read_lock();

	list_for_each_entry_rcu(device, &dma_device_list, global_node)

	list_for_each_entry_rcu(device, &dma_device_list, global_node) {

		if (dma_has_cap(DMA_PRIVATE, device->cap_mask))

			continue;

		list_for_each_entry(chan, &device->channels, device_node)

			if (chan->client_count)

				device->device_issue_pending(chan);

	}

	rcu_read_unlock();

}

EXPORT_SYMBOL(dma_issue_pending_all);
@@ -403,7 +409,8 @@ static struct dma_chan *nth_chan(enum dma_transaction_type cap, int n) 
	struct dma_chan *min = NULL;



	list_for_each_entry(device, &dma_device_list, global_node) {

		if (!dma_has_cap(cap, device->cap_mask))

		if (!dma_has_cap(cap, device->cap_mask) ||

		    dma_has_cap(DMA_PRIVATE, device->cap_mask))

			continue;

		list_for_each_entry(chan, &device->channels, device_node) {

			if (!chan->client_count)
@@ -452,9 +459,12 @@ static void dma_channel_rebalance(void) 
		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(device, &dma_device_list, global_node) {

		if (dma_has_cap(DMA_PRIVATE, device->cap_mask))

			continue;

		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)
@@ -473,6 +483,111 @@ static void dma_channel_rebalance(void) 
		}

}



static struct dma_chan *private_candidate(dma_cap_mask_t *mask, struct dma_device *dev)

{

	struct dma_chan *chan;

	struct dma_chan *ret = NULL;



	if (!__dma_device_satisfies_mask(dev, mask)) {

		pr_debug("%s: wrong capabilities\n", __func__);

		return NULL;

	}

	/* devices with multiple channels need special handling as we need to

	 * ensure that all channels are either private or public.

	 */

	if (dev->chancnt > 1 && !dma_has_cap(DMA_PRIVATE, dev->cap_mask))

		list_for_each_entry(chan, &dev->channels, device_node) {

			/* some channels are already publicly allocated */

			if (chan->client_count)

				return NULL;

		}



	list_for_each_entry(chan, &dev->channels, device_node) {

		if (chan->client_count) {

			pr_debug("%s: %s busy\n",

				 __func__, dev_name(&chan->dev));

			continue;

		}

		ret = chan;

		break;

	}



	return ret;

}



/**

 * dma_request_channel - try to allocate an exclusive channel

 * @mask: capabilities that the channel must satisfy

 * @fn: optional callback to disposition available channels

 * @fn_param: opaque parameter to pass to dma_filter_fn

 */

struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param)

{

	struct dma_device *device, *_d;

	struct dma_chan *chan = NULL;

	enum dma_state_client ack;

	int err;



	/* Find a channel */

	mutex_lock(&dma_list_mutex);

	list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {

		chan = private_candidate(mask, device);

		if (!chan)

			continue;



		if (fn)

			ack = fn(chan, fn_param);

		else

			ack = DMA_ACK;



		if (ack == DMA_ACK) {

			/* Found a suitable channel, try to grab, prep, and

			 * return it.  We first set DMA_PRIVATE to disable

			 * balance_ref_count as this channel will not be

			 * published in the general-purpose allocator

			 */

			dma_cap_set(DMA_PRIVATE, device->cap_mask);

			err = dma_chan_get(chan);



			if (err == -ENODEV) {

				pr_debug("%s: %s module removed\n", __func__,

					 dev_name(&chan->dev));

				list_del_rcu(&device->global_node);

			} else if (err)

				pr_err("dmaengine: failed to get %s: (%d)\n",

				       dev_name(&chan->dev), err);

			else

				break;

		} else if (ack == DMA_DUP) {

			pr_debug("%s: %s filter said DMA_DUP\n",

				 __func__, dev_name(&chan->dev));

		} else if (ack == DMA_NAK) {

			pr_debug("%s: %s filter said DMA_NAK\n",

				 __func__, dev_name(&chan->dev));

			break;

		} else

			WARN_ONCE(1, "filter_fn: unknown response?\n");

		chan = NULL;

	}

	mutex_unlock(&dma_list_mutex);



	pr_debug("%s: %s (%s)\n", __func__, chan ? "success" : "fail",

		 chan ? dev_name(&chan->dev) : NULL);



	return chan;

}

EXPORT_SYMBOL_GPL(__dma_request_channel);



void dma_release_channel(struct dma_chan *chan)

{

	mutex_lock(&dma_list_mutex);

	WARN_ONCE(chan->client_count != 1,

		  "chan reference count %d != 1\n", chan->client_count);

	dma_chan_put(chan);

	mutex_unlock(&dma_list_mutex);

}

EXPORT_SYMBOL_GPL(dma_release_channel);



/**

 * dma_chans_notify_available - broadcast available channels to the clients

 */
@@ -506,7 +621,9 @@ void dma_async_client_register(struct dma_client *client) 
	dmaengine_ref_count++;



	/* try to grab channels */

	list_for_each_entry_safe(device, _d, &dma_device_list, global_node)

	list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {

		if (dma_has_cap(DMA_PRIVATE, device->cap_mask))

			continue;

		list_for_each_entry(chan, &device->channels, device_node) {

			err = dma_chan_get(chan);

			if (err == -ENODEV) {
@@ -517,6 +634,7 @@ void dma_async_client_register(struct dma_client *client) 
				pr_err("dmaengine: failed to get %s: (%d)\n",

				       dev_name(&chan->dev), err);

		}

	}



	/* if this is the first reference and there were channels

	 * waiting we need to rebalance to get those channels
@@ -547,9 +665,12 @@ void dma_async_client_unregister(struct dma_client *client) 
	dmaengine_ref_count--;

	BUG_ON(dmaengine_ref_count < 0);

	/* drop channel references */

	list_for_each_entry(device, &dma_device_list, global_node)

	list_for_each_entry(device, &dma_device_list, global_node) {

		if (dma_has_cap(DMA_PRIVATE, device->cap_mask))

			continue;

		list_for_each_entry(chan, &device->channels, device_node)

			dma_chan_put(chan);

	}



	list_del(&client->global_node);

	mutex_unlock(&dma_list_mutex);
@@ -639,9 +760,11 @@ int dma_async_device_register(struct dma_device *device) 
		chan->slow_ref = 0;

		INIT_RCU_HEAD(&chan->rcu);

	}

	device->chancnt = chancnt;



	mutex_lock(&dma_list_mutex);

	if (dmaengine_ref_count)

	/* take references on public channels */

	if (dmaengine_ref_count && !dma_has_cap(DMA_PRIVATE, device->cap_mask))

		list_for_each_entry(chan, &device->channels, device_node) {

			/* if clients are already waiting for channels we need

			 * to take references on their behalf

include/linux/dmaengine.h

+16 −0
Original line number Diff line number Diff line
@@ -89,6 +89,7 @@ enum dma_transaction_type { 
	DMA_MEMSET,

	DMA_MEMCPY_CRC32C,

	DMA_INTERRUPT,

	DMA_PRIVATE,

	DMA_SLAVE,

};
@@ -223,6 +224,18 @@ struct dma_client; 
typedef enum dma_state_client (*dma_event_callback) (struct dma_client *client,

		struct dma_chan *chan, enum dma_state state);



/**

 * typedef dma_filter_fn - callback filter for dma_request_channel

 * @chan: channel to be reviewed

 * @filter_param: opaque parameter passed through dma_request_channel

 *

 * When this optional parameter is specified in a call to dma_request_channel a

 * suitable channel is passed to this routine for further dispositioning before

 * being returned.  Where 'suitable' indicates a non-busy channel that

 * satisfies the given capability mask.

 */

typedef enum dma_state_client (*dma_filter_fn)(struct dma_chan *chan, void *filter_param);



/**

 * struct dma_client - info on the entity making use of DMA services

 * @event_callback: func ptr to call when something happens
@@ -472,6 +485,9 @@ void dma_async_device_unregister(struct dma_device *device); 
void dma_run_dependencies(struct dma_async_tx_descriptor *tx);

struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);

void dma_issue_pending_all(void);

#define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)

struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param);

void dma_release_channel(struct dma_chan *chan);



/* --- Helper iov-locking functions --- */