Chapter 10
Pixel Pipeline (PxP) DMA-ENGINE Driver
10.1 Introduction
The Pixel Pipeline (PxP) DMA-ENGINE driver provides a unique API, which are
implemented as a dmaengine client that smooths over the details of different hardware
offload engine implementations. Typically, the users of PxP DMA-ENGINE driver
include EPDC driver, V4L2 Output driver, and the PxP user-space library.
10.2 Hardware Operation
The PxP driver uses PxP registers to interact with the hardware. For detailed hardware
operation, please refer to the i.MX 6Solo/6DualLite Multimedia Applications Processor
Reference Manual.
10.3 Software Operation
10.3.1 Key Data Structs
The PxP DMA Engine driver implementation depends on the DMA Engine Framework.
There are three important structs in the DMA Engine Framework which are extended by
the PxP driver: struct dma_device, struct dma_chan, struct dma_async_tx_descriptor. The
PxP driver implements several callback functions which are called by the DMA Engine
Framework (or DMA slave) when a DMA slave (client) interacts with the DMA Engine.
The PxP driver implements the following callback functions in struct dma_device:
device_alloc_chan_resources /* allocate resources and descriptors */
device_free_chan_resources /* release DMA channel's resources */
i.MX 6Solo/6DualLite Linux Reference Manual, Rev. L3.0.35_4.1.0, 09/2013
Freescale Semiconductor, Inc.
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