new file mode 100644
@@ -0,0 +1,271 @@
+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.
+
+DMA usage
+---------
+
+The slave DMA usage consists of following steps:
+
+ - Allocate a DMA slave channel
+
+ - Set slave and controller specific parameters
+
+ - Get a descriptor for transaction
+
+ - Submit the transaction
+
+ - Issue pending requests and wait for callback notification
+
+The details of these operations are:
+
+ 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_chan() API is used.
+
+ Interface:
+
+ .. code-block:: c
+
+ struct dma_chan *dma_request_chan(struct device *dev, const char *name);
+
+ Which will find and return the ``name`` DMA channel associated with the 'dev'
+ device. The association is done via DT, ACPI or board file based
+ dma_slave_map matching table.
+
+ 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:
+
+ .. code-block:: c
+
+ 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:
+
+ .. code-block:: c
+
+ 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:
+
+
+ .. code-block:: c
+
+ 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_async().
+
+ 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:
+
+ .. code-block:: c
+
+ 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:
+
+ .. code-block:: c
+
+ void dma_async_issue_pending(struct dma_chan *chan);
+
+Further APIs:
+------------
+
+ 1. Terminate APIs
+
+ .. code-block:: c
+
+ int dmaengine_terminate_sync(struct dma_chan *chan)
+ int dmaengine_terminate_async(struct dma_chan *chan)
+ int dmaengine_terminate_all(struct dma_chan *chan) /* DEPRECATED */
+
+ 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.
+
+ Two variants of this function are available.
+
+ dmaengine_terminate_async() might not wait until the DMA has been fully
+ stopped or until any running complete callbacks have finished. But it is
+ possible to call dmaengine_terminate_async() from atomic context or from
+ within a complete callback. dmaengine_synchronize() must be called before it
+ is safe to free the memory accessed by the DMA transfer or free resources
+ accessed from within the complete callback.
+
+ dmaengine_terminate_sync() will wait for the transfer and any running
+ complete callbacks to finish before it returns. But the function must not be
+ called from atomic context or from within a complete callback.
+
+ dmaengine_terminate_all() is deprecated and should not be used in new code.
+
+ 2. Pause API
+
+ .. code-block:: c
+
+ int dmaengine_pause(struct dma_chan *chan)
+
+ This pauses activity on the DMA channel without data loss.
+
+ 3. Resume API
+
+ .. code-block:: c
+
+ 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. Check Txn complete
+
+ .. code-block:: c
+
+ 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.
+
+ 5. Synchronize termination API
+
+ .. code-block:: c
+
+ void dmaengine_synchronize(struct dma_chan *chan)
+
+ Synchronize the termination of the DMA channel to the current context.
+
+ This function should be used after dmaengine_terminate_async() to synchronize
+ the termination of the DMA channel to the current context. The function will
+ wait for the transfer and any running complete callbacks to finish before it
+ returns.
+
+ If dmaengine_terminate_async() is used to stop the DMA channel this function
+ must be called before it is safe to free memory accessed by previously
+ submitted descriptors or to free any resources accessed within the complete
+ callback of previously submitted descriptors.
+
+ The behavior of this function is undefined if dma_async_issue_pending() has
+ been called between dmaengine_terminate_async() and this function.
deleted file mode 100644
@@ -1,222 +0,0 @@
- 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_chan() API is used.
-
- Interface:
- struct dma_chan *dma_request_chan(struct device *dev, const char *name);
-
- Which will find and return the 'name' DMA channel associated with the 'dev'
- device. The association is done via DT, ACPI or board file based
- dma_slave_map matching table.
-
- 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_async().
-
- 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_sync(struct dma_chan *chan)
- int dmaengine_terminate_async(struct dma_chan *chan)
- int dmaengine_terminate_all(struct dma_chan *chan) /* DEPRECATED */
-
- 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.
-
- Two variants of this function are available.
-
- dmaengine_terminate_async() might not wait until the DMA has been fully
- stopped or until any running complete callbacks have finished. But it is
- possible to call dmaengine_terminate_async() from atomic context or from
- within a complete callback. dmaengine_synchronize() must be called before it
- is safe to free the memory accessed by the DMA transfer or free resources
- accessed from within the complete callback.
-
- dmaengine_terminate_sync() will wait for the transfer and any running
- complete callbacks to finish before it returns. But the function must not be
- called from atomic context or from within a complete callback.
-
- dmaengine_terminate_all() is deprecated and should not be used in new code.
-
-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.
-
-5. void dmaengine_synchronize(struct dma_chan *chan)
-
- Synchronize the termination of the DMA channel to the current context.
-
- This function should be used after dmaengine_terminate_async() to synchronize
- the termination of the DMA channel to the current context. The function will
- wait for the transfer and any running complete callbacks to finish before it
- returns.
-
- If dmaengine_terminate_async() is used to stop the DMA channel this function
- must be called before it is safe to free memory accessed by previously
- submitted descriptors or to free any resources accessed within the complete
- callback of previously submitted descriptors.
-
- The behavior of this function is undefined if dma_async_issue_pending() has
- been called between dmaengine_terminate_async() and this function.
@@ -16,6 +16,17 @@ driver writers.
provider
+DMAEngine client documentation
+------------------------------
+
+This book is a guide to device driver writers on how to use the Slave-DMA
+API of the DMAEngine. This is applicable only for slave DMA usage only.
+
+.. toctree::
+ :maxdepth: 1
+
+ client
+
.. only:: subproject
Indices
This converts client API file with some format changes for RST style Signed-off-by: Vinod Koul <vinod.koul@intel.com> --- Documentation/dmaengine/client.rst | 271 +++++++++++++++++++++++++++++++++++++ Documentation/dmaengine/client.txt | 222 ------------------------------ Documentation/dmaengine/index.rst | 11 ++ 3 files changed, 282 insertions(+), 222 deletions(-) create mode 100644 Documentation/dmaengine/client.rst delete mode 100644 Documentation/dmaengine/client.txt