BeagleBoard/DSP Clarification

This article tries to explain all the different Linux DSP systems for OMAP3 chips (e.g. used on BeagleBoard), how they are similar and different.

dsp-gateway
DSP Gateway was developed by Nokia for the Maemo Internet Tablets. It's the first open implementation and currently the more open. The open code consists not only of the Linux kernel side, but also the DSP operating system. Unfortunately the development is essentially halted.

It works on OMAP1 and OMAP2, it's production ready, used on the Nokia N800 and N810, it follows Linux standards and it's close to upstream acceptance. There's code for OMAP3 but it hasn't been thoroughly tested.

It is maintained by Hiroshi DOYU.

There are a few user space applications that use it. Essentially GStreamer Nokia DSP plug-ins and a few others developed by the Maemo community.

However, it's mostly unmaintained.

dsp-bridge
tidspbridge originally developed by TI, after its release in open source it has received many more contributions, primarily from TI and Nokia.

It still doesn't meet Linux standards although there has been a lot of progress. Only the ARM side is available as open source; unlike the dsp-gateway, the DSP side is completely closed.

There has been a lot of work spent into cleaning up the code to live up to linux standards, and currently it's on the staging tree with a strong push to merge it on mainline.

It shares the mailbox code with dsp-gateway, and soon iommu too.

There are more user-space applications using it, including gst-dsp directly, gst-openmax and gst-goo through TI's OpenMAX IL implementation which is also open source. Leonora is a project implementing the Theora codec on the DSP, and is a good example of non-trivial code running on the DSP and communicating with a process running on the ARM core.

For documentation and project overview, visit: TI DSP/Bridge project

dsp-link
A slimmer version of the dsp-bridge, also developed by TI. It supports a wide variety of devices (e.g. DaVinci, OMAP2, OMAP3, and discreet GPP+DSP devices).

The kernel driver doesn't meet the Linux kernel coding conventions. The sources haven't been submitted for review, and it is not currently planned to be merged into upstream kernels.

Some of the key differences with respect to dsp-bridge is the lack of advanced power management features (like DVFS and SmartReflex), and lack of dynamic MMU support.

Codec Engine and DMAI have been built upon it, and there are GStreamer plug-ins provided by TI to use the algorithms.

Unlike the other implementations, it has strong support from the Angstrom distribution precisely because of wider platform support.

See DSPLink articles in Texas Instruments Embedded Processors Wiki, too.

syslink
For OMAP4 a new consolidated bridge is being developed syslink. It's an evolution of previous IPC mechanisms, reusing elements such as iommu and mailbox, and incorporating ideas such as moving the module loading to user-space from dsp-gateway.

Unlike it's predecessors it's supposed to be upstreamed since the get-go, and in fact some patches are already integrated (in iommu and mailbox).

Interesting threads

 * bridge vs link
 * different power management