[PATCH 5/5] Add DMA engine driver for Freescale MPC85xx processors.
dan.j.williams at intel.com
Mon Sep 10 08:10:12 EST 2007
On 9/9/07, Timur Tabi <timur at freescale.com> wrote:
> Dan Williams wrote:
> > This routine implies that there is a piece of code somewhere that
> > wants to select which channels it can use. A similar effect can be
> > achieved by registering a dma_client with the dmaengine interface
> > ('dma_async_client_register'). Then when the client code makes a call
> > to 'dma_async_client_chan_request' it receives a 'dma_event_callback'
> > for each channel in the system. It will also be asynchronously
> > notified of channels entering and leaving the system. The goal is to
> > share a common infrastructure for channel management.
> Are you familiar with the "flat device tree" used for PowerPC systems? The
> "piece of code somewhere" is the device tree subsystem that parses the device
> tree, which is compiled from the .dts files in arch/powerpc/boot/dts.
> The FDT is how PowerPC systems specify hardware configuration. In the case of
> 85xx, the FDT contains entries for each DMA device (typically 2), and the
> entries contain sub-entries for each DMA channel as well as the address of the
> register sets for each channel.
Ahh, ok then this code is replacing what would normally be handled by
the PCI bus enumeration code, or the platform device registrations for
iop-adma in arch/arm/mach-iop13xx. Sorry for the noise with this
> Timur Tabi
> Linux Kernel Developer @ Freescale
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