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diff --git a/Documentation/dmaengine/client.txt b/Documentation/dmaengine/client.txt
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+                        DMA Engine API Guide
+                        ====================
+                 Vinod Koul <vinod dot koul at intel.com>
+NOTE: For DMA Engine usage in async_tx please see:
+        Documentation/crypto/async-tx-api.txt
+Below is a guide to device driver writers on how to use the Slave-DMA API of the
+DMA Engine. This is applicable only for slave DMA usage only.
+The slave DMA usage consists of following steps:
+1. Allocate a DMA slave channel
+2. Set slave and controller specific parameters
+3. Get a descriptor for transaction
+4. Submit the transaction
+5. Issue pending requests and wait for callback notification
+1. Allocate a DMA slave channel
+   Channel allocation is slightly different in the slave DMA context,
+   client drivers typically need a channel from a particular DMA
+   controller only and even in some cases a specific channel is desired.
+   To request a channel dma_request_channel() API is used.
+   Interface:
+        struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
+                        dma_filter_fn filter_fn,
+                        void *filter_param);
+   where dma_filter_fn is defined as:
+        typedef bool (*dma_filter_fn)(struct dma_chan *chan, void *filter_param);
+   The 'filter_fn' parameter is optional, but highly recommended for
+   slave and cyclic channels as they typically need to obtain a specific
+   DMA channel.
+   When the optional 'filter_fn' parameter is NULL, dma_request_channel()
+   simply returns the first channel that satisfies the capability mask.
+   Otherwise, the 'filter_fn' routine will be called once for each free
+   channel which has a capability in 'mask'.  'filter_fn' is expected to
+   return 'true' when the desired DMA channel is found.
+   A channel allocated via this interface is exclusive to the caller,
+   until dma_release_channel() is called.
+2. Set slave and controller specific parameters
+   Next step is always to pass some specific information to the DMA
+   driver.  Most of the generic information which a slave DMA can use
+   is in struct dma_slave_config.  This allows the clients to specify
+   DMA direction, DMA addresses, bus widths, DMA burst lengths etc
+   for the peripheral.
+   If some DMA controllers have more parameters to be sent then they
+   should try to embed struct dma_slave_config in their controller
+   specific structure. That gives flexibility to client to pass more
+   parameters, if required.
+   Interface:
+        int dmaengine_slave_config(struct dma_chan *chan,
+                                  struct dma_slave_config *config)
+   Please see the dma_slave_config structure definition in dmaengine.h
+   for a detailed explanation of the struct members.  Please note
+   that the 'direction' member will be going away as it duplicates the
+   direction given in the prepare call.
+3. Get a descriptor for transaction
+   For slave usage the various modes of slave transfers supported by the
+   DMA-engine are:
+   slave_sg     - DMA a list of scatter gather buffers from/to a peripheral
+   dma_cyclic   - Perform a cyclic DMA operation from/to a peripheral till the
+                  operation is explicitly stopped.
+   interleaved_dma - This is common to Slave as well as M2M clients. For slave
+                 address of devices' fifo could be already known to the driver.
+                 Various types of operations could be expressed by setting
+                 appropriate values to the 'dma_interleaved_template' members.
+   A non-NULL return of this transfer API represents a "descriptor" for
+   the given transaction.
+   Interface:
+        struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
+                struct dma_chan *chan, struct scatterlist *sgl,
+                unsigned int sg_len, enum dma_data_direction direction,
+                unsigned long flags);
+        struct dma_async_tx_descriptor *dmaengine_prep_dma_cyclic(
+                struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
+                size_t period_len, enum dma_data_direction direction);
+        struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
+                struct dma_chan *chan, struct dma_interleaved_template *xt,
+                unsigned long flags);
+   The peripheral driver is expected to have mapped the scatterlist for
+   the DMA operation prior to calling dmaengine_prep_slave_sg(), and must
+   keep the scatterlist mapped until the DMA operation has completed.
+   The scatterlist must be mapped using the DMA struct device.
+   If a mapping needs to be synchronized later, dma_sync_*_for_*() must be
+   called using the DMA struct device, too.
+   So, normal setup should look like this:
+        nr_sg = dma_map_sg(chan->device->dev, sgl, sg_len);
+        if (nr_sg == 0)
+                /* error */
+        desc = dmaengine_prep_slave_sg(chan, sgl, nr_sg, direction, flags);
+   Once a descriptor has been obtained, the callback information can be
+   added and the descriptor must then be submitted.  Some DMA engine
+   drivers may hold a spinlock between a successful preparation and
+   submission so it is important that these two operations are closely
+   paired.
+   Note:
+        Although the async_tx API specifies that completion callback
+        routines cannot submit any new operations, this is not the
+        case for slave/cyclic DMA.
+        For slave DMA, the subsequent transaction may not be available
+        for submission prior to callback function being invoked, so
+        slave DMA callbacks are permitted to prepare and submit a new
+        transaction.
+        For cyclic DMA, a callback function may wish to terminate the
+        DMA via dmaengine_terminate_all().
+        Therefore, it is important that DMA engine drivers drop any
+        locks before calling the callback function which may cause a
+        deadlock.
+        Note that callbacks will always be invoked from the DMA
+        engines tasklet, never from interrupt context.
+4. Submit the transaction
+   Once the descriptor has been prepared and the callback information
+   added, it must be placed on the DMA engine drivers pending queue.
+   Interface:
+        dma_cookie_t dmaengine_submit(struct dma_async_tx_descriptor *desc)
+   This returns a cookie can be used to check the progress of DMA engine
+   activity via other DMA engine calls not covered in this document.
+   dmaengine_submit() will not start the DMA operation, it merely adds
+   it to the pending queue.  For this, see step 5, dma_async_issue_pending.
+5. Issue pending DMA requests and wait for callback notification
+   The transactions in the pending queue can be activated by calling the
+   issue_pending API. If channel is idle then the first transaction in
+   queue is started and subsequent ones queued up.
+   On completion of each DMA operation, the next in queue is started and
+   a tasklet triggered. The tasklet will then call the client driver
+   completion callback routine for notification, if set.
+   Interface:
+        void dma_async_issue_pending(struct dma_chan *chan);
+Further APIs:
+1. int dmaengine_terminate_all(struct dma_chan *chan)
+   This causes all activity for the DMA channel to be stopped, and may
+   discard data in the DMA FIFO which hasn't been fully transferred.
+   No callback functions will be called for any incomplete transfers.
+2. int dmaengine_pause(struct dma_chan *chan)
+   This pauses activity on the DMA channel without data loss.
+3. int dmaengine_resume(struct dma_chan *chan)
+   Resume a previously paused DMA channel.  It is invalid to resume a
+   channel which is not currently paused.
+4. enum dma_status dma_async_is_tx_complete(struct dma_chan *chan,
+        dma_cookie_t cookie, dma_cookie_t *last, dma_cookie_t *used)
+   This can be used to check the status of the channel.  Please see
+   the documentation in include/linux/dmaengine.h for a more complete
+   description of this API.
+   This can be used in conjunction with dma_async_is_complete() and
+   the cookie returned from dmaengine_submit() to check for
+   completion of a specific DMA transaction.
+   Note:
+        Not all DMA engine drivers can return reliable information for
+        a running DMA channel.  It is recommended that DMA engine users
+        pause or stop (via dmaengine_terminate_all()) the channel before
+        using this API.

diff --git a/Documentation/dmaengine/client.txt b/Documentation/dmaengine/client.txt new file mode 100644 index 000000000000..11fb87ff6cd0 --- /dev/null +++ b/Documentation/dmaengine/client.txt
@@ -0,0 +1,199 @@
	1	DMA Engine API Guide
	2	====================
	3
	4	Vinod Koul <vinod dot koul at intel.com>
	5
	6	NOTE: For DMA Engine usage in async_tx please see:
	7	Documentation/crypto/async-tx-api.txt
	8
	9
	10	Below is a guide to device driver writers on how to use the Slave-DMA API of the
	11	DMA Engine. This is applicable only for slave DMA usage only.
	12
	13	The slave DMA usage consists of following steps:
	14	1. Allocate a DMA slave channel
	15	2. Set slave and controller specific parameters
	16	3. Get a descriptor for transaction
	17	4. Submit the transaction
	18	5. Issue pending requests and wait for callback notification
	19
	20	1. Allocate a DMA slave channel
	21
	22	Channel allocation is slightly different in the slave DMA context,
	23	client drivers typically need a channel from a particular DMA
	24	controller only and even in some cases a specific channel is desired.
	25	To request a channel dma_request_channel() API is used.
	26
	27	Interface:
	28	struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
	29	dma_filter_fn filter_fn,
	30	void *filter_param);
	31	where dma_filter_fn is defined as:
	32	typedef bool (dma_filter_fn)(struct dma_chan chan, void *filter_param);
	33
	34	The 'filter_fn' parameter is optional, but highly recommended for
	35	slave and cyclic channels as they typically need to obtain a specific
	36	DMA channel.
	37
	38	When the optional 'filter_fn' parameter is NULL, dma_request_channel()
	39	simply returns the first channel that satisfies the capability mask.
	40
	41	Otherwise, the 'filter_fn' routine will be called once for each free
	42	channel which has a capability in 'mask'. 'filter_fn' is expected to
	43	return 'true' when the desired DMA channel is found.
	44
	45	A channel allocated via this interface is exclusive to the caller,
	46	until dma_release_channel() is called.
	47
	48	2. Set slave and controller specific parameters
	49
	50	Next step is always to pass some specific information to the DMA
	51	driver. Most of the generic information which a slave DMA can use
	52	is in struct dma_slave_config. This allows the clients to specify
	53	DMA direction, DMA addresses, bus widths, DMA burst lengths etc
	54	for the peripheral.
	55
	56	If some DMA controllers have more parameters to be sent then they
	57	should try to embed struct dma_slave_config in their controller
	58	specific structure. That gives flexibility to client to pass more
	59	parameters, if required.
	60
	61	Interface:
	62	int dmaengine_slave_config(struct dma_chan *chan,
	63	struct dma_slave_config *config)
	64
	65	Please see the dma_slave_config structure definition in dmaengine.h
	66	for a detailed explanation of the struct members. Please note
	67	that the 'direction' member will be going away as it duplicates the
	68	direction given in the prepare call.
	69
	70	3. Get a descriptor for transaction
	71
	72	For slave usage the various modes of slave transfers supported by the
	73	DMA-engine are:
	74
	75	slave_sg - DMA a list of scatter gather buffers from/to a peripheral
	76	dma_cyclic - Perform a cyclic DMA operation from/to a peripheral till the
	77	operation is explicitly stopped.
	78	interleaved_dma - This is common to Slave as well as M2M clients. For slave
	79	address of devices' fifo could be already known to the driver.
	80	Various types of operations could be expressed by setting
	81	appropriate values to the 'dma_interleaved_template' members.
	82
	83	A non-NULL return of this transfer API represents a "descriptor" for
	84	the given transaction.
	85
	86	Interface:
	87	struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
	88	struct dma_chan chan, struct scatterlist sgl,
	89	unsigned int sg_len, enum dma_data_direction direction,
	90	unsigned long flags);
	91
	92	struct dma_async_tx_descriptor *dmaengine_prep_dma_cyclic(
	93	struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
	94	size_t period_len, enum dma_data_direction direction);
	95
	96	struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
	97	struct dma_chan chan, struct dma_interleaved_template xt,
	98	unsigned long flags);
	99
	100	The peripheral driver is expected to have mapped the scatterlist for
	101	the DMA operation prior to calling dmaengine_prep_slave_sg(), and must
	102	keep the scatterlist mapped until the DMA operation has completed.
	103	The scatterlist must be mapped using the DMA struct device.
	104	If a mapping needs to be synchronized later, dma_sync__for_() must be
	105	called using the DMA struct device, too.
	106	So, normal setup should look like this:
	107
	108	nr_sg = dma_map_sg(chan->device->dev, sgl, sg_len);
	109	if (nr_sg == 0)
	110	/* error */
	111
	112	desc = dmaengine_prep_slave_sg(chan, sgl, nr_sg, direction, flags);
	113
	114	Once a descriptor has been obtained, the callback information can be
	115	added and the descriptor must then be submitted. Some DMA engine
	116	drivers may hold a spinlock between a successful preparation and
	117	submission so it is important that these two operations are closely
	118	paired.
	119
	120	Note:
	121	Although the async_tx API specifies that completion callback
	122	routines cannot submit any new operations, this is not the
	123	case for slave/cyclic DMA.
	124
	125	For slave DMA, the subsequent transaction may not be available
	126	for submission prior to callback function being invoked, so
	127	slave DMA callbacks are permitted to prepare and submit a new
	128	transaction.
	129
	130	For cyclic DMA, a callback function may wish to terminate the
	131	DMA via dmaengine_terminate_all().
	132
	133	Therefore, it is important that DMA engine drivers drop any
	134	locks before calling the callback function which may cause a
	135	deadlock.
	136
	137	Note that callbacks will always be invoked from the DMA
	138	engines tasklet, never from interrupt context.
	139
	140	4. Submit the transaction
	141
	142	Once the descriptor has been prepared and the callback information
	143	added, it must be placed on the DMA engine drivers pending queue.
	144
	145	Interface:
	146	dma_cookie_t dmaengine_submit(struct dma_async_tx_descriptor *desc)
	147
	148	This returns a cookie can be used to check the progress of DMA engine
	149	activity via other DMA engine calls not covered in this document.
	150
	151	dmaengine_submit() will not start the DMA operation, it merely adds
	152	it to the pending queue. For this, see step 5, dma_async_issue_pending.
	153
	154	5. Issue pending DMA requests and wait for callback notification
	155
	156	The transactions in the pending queue can be activated by calling the
	157	issue_pending API. If channel is idle then the first transaction in
	158	queue is started and subsequent ones queued up.
	159
	160	On completion of each DMA operation, the next in queue is started and
	161	a tasklet triggered. The tasklet will then call the client driver
	162	completion callback routine for notification, if set.
	163
	164	Interface:
	165	void dma_async_issue_pending(struct dma_chan *chan);
	166
	167	Further APIs:
	168
	169	1. int dmaengine_terminate_all(struct dma_chan *chan)
	170
	171	This causes all activity for the DMA channel to be stopped, and may
	172	discard data in the DMA FIFO which hasn't been fully transferred.
	173	No callback functions will be called for any incomplete transfers.
	174
	175	2. int dmaengine_pause(struct dma_chan *chan)
	176
	177	This pauses activity on the DMA channel without data loss.
	178
	179	3. int dmaengine_resume(struct dma_chan *chan)
	180
	181	Resume a previously paused DMA channel. It is invalid to resume a
	182	channel which is not currently paused.
	183
	184	4. enum dma_status dma_async_is_tx_complete(struct dma_chan *chan,
	185	dma_cookie_t cookie, dma_cookie_t last, dma_cookie_t used)
	186
	187	This can be used to check the status of the channel. Please see
	188	the documentation in include/linux/dmaengine.h for a more complete
	189	description of this API.
	190
	191	This can be used in conjunction with dma_async_is_complete() and
	192	the cookie returned from dmaengine_submit() to check for
	193	completion of a specific DMA transaction.
	194
	195	Note:
	196	Not all DMA engine drivers can return reliable information for
	197	a running DMA channel. It is recommended that DMA engine users
	198	pause or stop (via dmaengine_terminate_all()) the channel before
	199	using this API.