dmaengine: make clients responsible for managing channels (d379b01e) · Commits · 戴 / test

drivers/dma/dmaengine.c

+111 −106

Original line number	Diff line number	Diff line
		@@ -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;

		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", (chan->client ? 1 : 0));
		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) {
		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);
		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;
		}
		} 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;
		@@ -217,70 +240,57 @@ 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) {
		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);
		}
		}
		list_for_each_entry(client, &dma_client_list, global_node)
		dma_client_chan_alloc(client);

		mutex_unlock(&dma_list_mutex);
		}

		/**
		* dma_async_client_register - allocate and register a &dma_client
		* @event_callback: callback for notification of channel addition/removal
		* dma_chans_notify_available - tell the clients that a channel is going away
		* @chan: channel on its way out
		*/
		struct dma_client *dma_async_client_register(dma_event_callback event_callback)
		static void dma_clients_notify_removed(struct dma_chan *chan)
		{
		struct dma_client *client;
		enum dma_state_client ack;

		client = kzalloc(sizeof(*client), GFP_KERNEL);
		if (!client)
		return NULL;
		mutex_lock(&dma_list_mutex);

		INIT_LIST_HEAD(&client->channels);
		spin_lock_init(&client->lock);
		client->chans_desired = 0;
		client->chan_count = 0;
		client->event_callback = event_callback;
		list_for_each_entry(client, &dma_client_list, global_node) {
		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);
		}
		}

		mutex_unlock(&dma_list_mutex);
		}

		/**
		* dma_async_client_register - register a &dma_client
		* @client: ptr to a client structure with valid 'event_callback' and 'cap_mask'
		*/
		void dma_async_client_register(struct dma_client *client)
		{
		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);

drivers/dma/ioatdma.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -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);
		}

drivers/dma/ioatdma.h

+0 −3

Original line number	Diff line number	Diff line
		@@ -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

include/linux/dmaengine.h

+35 −23

Original line number	Diff line number	Diff line
		@@ -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)
		{

net/core/dev.c

+78 −34

Original line number	Diff line number	Diff line
		@@ -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)
		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);
		rcu_read_unlock();
		}
		}
		#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)
		{
		spin_lock(&net_dma_event_lock);
		switch (event) {
		case DMA_RESOURCE_ADDED:
		net_dma_count++;
		net_dma_rebalance();
		static enum dma_state_client
		netdev_dma_event(struct dma_client client, struct dma_chan chan,
		enum dma_state state)
		{
		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;
		}

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