path: root/Documentation/dmaengine
AgeCommit message (Collapse)Author
2016-08-08dmaengine: documentation to the new callback mechanismDave Jiang
Adding documentation in dmaengine/provider.txt on the usage of callback with result, callback_result, function pointer to retrieve transanction result from a DMA submission. Signed-off-by: Dave Jiang <dave.jiang@intel.com> Reviewed-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2016-06-03Documentation: dmaengine: fix typo for device_resumeNiklas Söderlund
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2016-01-06Merge branch 'topic/async' into for-linusVinod Koul
2015-12-18dmaengine: core: Introduce new, universal API to request a channelPeter Ujfalusi
The two API function can cover most, if not all current APIs used to request a channel. With minimal effort dmaengine drivers, platforms and dmaengine user drivers can be converted to use the two function. struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask); To request any channel matching with the requested capabilities, can be used to request channel for memcpy, memset, xor, etc where no hardware synchronization is needed. struct dma_chan *dma_request_chan(struct device *dev, const char *name); To request a slave channel. The dma_request_chan() will try to find the channel via DT, ACPI or in case if the kernel booted in non DT/ACPI mode it will use a filter lookup table and retrieves the needed information from the dma_slave_map provided by the DMA drivers. This legacy mode needs changes in platform code, in dmaengine drivers and finally the dmaengine user drivers can be converted: For each dmaengine driver an array of DMA device, slave and the parameter for the filter function needs to be added: static const struct dma_slave_map da830_edma_map[] = { { "davinci-mcasp.0", "rx", EDMA_FILTER_PARAM(0, 0) }, { "davinci-mcasp.0", "tx", EDMA_FILTER_PARAM(0, 1) }, { "davinci-mcasp.1", "rx", EDMA_FILTER_PARAM(0, 2) }, { "davinci-mcasp.1", "tx", EDMA_FILTER_PARAM(0, 3) }, { "davinci-mcasp.2", "rx", EDMA_FILTER_PARAM(0, 4) }, { "davinci-mcasp.2", "tx", EDMA_FILTER_PARAM(0, 5) }, { "spi_davinci.0", "rx", EDMA_FILTER_PARAM(0, 14) }, { "spi_davinci.0", "tx", EDMA_FILTER_PARAM(0, 15) }, { "da830-mmc.0", "rx", EDMA_FILTER_PARAM(0, 16) }, { "da830-mmc.0", "tx", EDMA_FILTER_PARAM(0, 17) }, { "spi_davinci.1", "rx", EDMA_FILTER_PARAM(0, 18) }, { "spi_davinci.1", "tx", EDMA_FILTER_PARAM(0, 19) }, }; This information is going to be needed by the dmaengine driver, so modification to the platform_data is needed, and the driver map should be added to the pdata of the DMA driver: da8xx_edma0_pdata.slave_map = da830_edma_map; da8xx_edma0_pdata.slavecnt = ARRAY_SIZE(da830_edma_map); The DMA driver then needs to configure the needed device -> filter_fn mapping before it registers with dma_async_device_register() : ecc->dma_slave.filter_map.map = info->slave_map; ecc->dma_slave.filter_map.mapcnt = info->slavecnt; ecc->dma_slave.filter_map.fn = edma_filter_fn; When neither DT or ACPI lookup is available the dma_request_chan() will try to match the requester's device name with the filter_map's list of device names, when a match found it will use the information from the dma_slave_map to get the channel with the dma_get_channel() internal function. Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2015-11-16dmaengine: Add transfer termination synchronization supportLars-Peter Clausen
The DMAengine API has a long standing race condition that is inherent to the API itself. Calling dmaengine_terminate_all() is supposed to stop and abort any pending or active transfers that have previously been submitted. Unfortunately it is possible that this operation races against a currently running (or with some drivers also scheduled) completion callback. Since the API allows dmaengine_terminate_all() to be called from atomic context as well as from within a completion callback it is not possible to synchronize to the execution of the completion callback from within dmaengine_terminate_all() itself. This means that a user of the DMAengine API does not know when it is safe to free resources used in the completion callback, which can result in a use-after-free race condition. This patch addresses the issue by introducing an explicit synchronization primitive to the DMAengine API called dmaengine_synchronize(). The existing dmaengine_terminate_all() is deprecated in favor of dmaengine_terminate_sync() and dmaengine_terminate_async(). The former aborts all pending and active transfers and synchronizes to the current context, meaning it will wait until all running completion callbacks have finished. This means it is only possible to call this function from non-atomic context. The later function does not synchronize, but can still be used in atomic context or from within a complete callback. It has to be followed up by dmaengine_synchronize() before a client can free the resources used in a completion callback. In addition to this the semantics of the device_terminate_all() callback are slightly relaxed by this patch. It is now OK for a driver to only schedule the termination of the active transfer, but does not necessarily have to wait until the DMA controller has completely stopped. The driver must ensure though that the controller has stopped and no longer accesses any memory when the device_synchronize() callback returns. This was in part done since most drivers do not pay attention to this anyway at the moment and to emphasize that this needs to be done when the device_synchronize() callback is implemented. But it also helps with implementing support for devices where stopping the controller can require operations that may sleep. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2015-08-17Documentation: dmaengine: Add DMA_CTRL_REUSE documentationVinod Koul
Signed-off-by: Vinod Koul <vinod.koul@intel.com> Acked-by:Robert Jarzmik <robert.jarzmik@free.fr>
2015-08-17Documentation: dmaengine: fix the DMA_CTRL_ACK documentationVinod Koul
As discussed recently the meaning of DMA_CTRL_ACK is that a desc cannot be reused by provider until the client acknowledges receipt, i.e. has has a chance to establish any dependency chains. So update documentation Signed-off-by: Vinod Koul <vinod.koul@intel.com> Acked-by:Robert Jarzmik <robert.jarzmik@free.fr>
2015-06-25Merge branch 'topic/pxa' into for-linusVinod Koul
2015-06-17Documentation: dmaengine: document DMA_CTRL_ACKRobert Jarzmik
Add documentation about acking the transfers, and their reusability. Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2015-05-26Documentation: dmaengine: pxa-dma designRobert Jarzmik
Document the new design of the pxa dma driver. Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2015-02-18Merge branch 'for-linus' of git://git.infradead.org/users/vkoul/slave-dmaLinus Torvalds
Pull dmaengine updates from Vinod Koul: "This update brings: - the big cleanup up by Maxime for device control and slave capabilities. This makes the API much cleaner. - new IMG MDC driver by Andrew - new Renesas R-Car Gen2 DMA Controller driver by Laurent along with bunch of fixes on rcar drivers - odd fixes and updates spread over driver" * 'for-linus' of git://git.infradead.org/users/vkoul/slave-dma: (130 commits) dmaengine: pl330: add DMA_PAUSE feature dmaengine: pl330: improve pl330_tx_status() function dmaengine: rcar-dmac: Disable channel 0 when using IOMMU dmaengine: rcar-dmac: Work around descriptor mode IOMMU errata dmaengine: rcar-dmac: Allocate hardware descriptors with DMAC device dmaengine: rcar-dmac: Fix oops due to unintialized list in error ISR dmaengine: rcar-dmac: Fix spinlock issues in interrupt dmaenegine: edma: fix sparse warnings dmaengine: rcar-dmac: Fix uninitialized variable usage dmaengine: shdmac: extend PM methods dmaengine: shdmac: use SET_RUNTIME_PM_OPS() dmaengine: pl330: fix bug that cause start the same descs in cyclic dmaengine: at_xdmac: allow muliple dwidths when doing slave transfers dmaengine: at_xdmac: simplify channel configuration stuff dmaengine: at_xdmac: introduce save_cc field dmaengine: at_xdmac: wait for in-progress transaction to complete after pausing a channel ioat: fail self-test if wait_for_completion times out dmaengine: dw: define DW_DMA_MAX_NR_MASTERS dmaengine: dw: amend description of dma_dev field dmatest: move src_off, dst_off, len inside loop ...
2014-12-29Update of Documentation/dmaengine/00-INDEXHenrik Austad
- client.txt was moved by f36d2e67 (dmaengine: Move the current doc to a folder of its own) - dmatmest.txt was moved by 935cdb56 (dmanegine: move dmatest.txt to dmaengine folder) - provider.txt was added by c4d2ae967 (Documentation: dmaengine: Add a documentation for the dma controller API). Cc: Maxime Ripard <maxime.ripard@free-electrons.com> Cc: Vinod Koul <vinod.koul@intel.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: dmaengine@vger.kernel.org Cc: linux-doc@vger.kernel.org Signed-off-by: Henrik Austad <henrik@austad.us> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2014-12-22Documentation: dmaengine: clarify dma_slave_config expectationsVinod Koul
dma_slave_config is expected to be set for slave operations Only, not for memcpy ones Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2014-12-22Documentation: dmaengine: Update the documentationMaxime Ripard
Now that we have splitted device_control and removed device_slave_caps in favor of a few dma_device variables, update the documentation accordingly. Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2014-11-06Documentation: dmanegine: move dmatest.txt to dmaengine folderVinod Koul
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2014-11-06Documentation: dmaengine: Add a documentation for the dma controller APIMaxime Ripard
The dmaengine is neither trivial nor properly documented at the moment, which means a lot of trial and error development, which is not that good for such a central piece of the system. Attempt at making such a documentation. Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> [fixed some minor typos] Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2014-11-06Documentation: dmaengine: Move the current doc to a folder of its ownMaxime Ripard
Move the current client-side documentation to a subfolder to prepare the introduction of a provider-side API documentation. Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>