[Letux-kernel] LetuxOS: Kernel: m-rc 5.3-rc1 successful

H. Nikolaus Schaller hns at goldelico.com
Tue Jul 30 17:21:18 CEST 2019


> Am 30.07.2019 um 16:29 schrieb N. Jackson <nljlistbox2 at gmail.com>:
> At 10:22 +0200 on Tuesday 2019-07-23, H. Nikolaus Schaller wrote:
>> a) the AESS patches by Peter we are carrying along did no
>> longer compile.
>> Reason is that some members of the dai_link struct have
>> been replaced by pointers to other structs. The macros
>> used to initialize them can no longer be used.
>> Therefore I have simply disabled the offending code
>> lines.
>> Note: this is not yet fixed in the letux/pyra-minimal tree.
>> Generally we need someone who looks at this code pile
>> and brings them into a better shape. Ideally it would
>> be made working incl. AESS firmware load and pushed
>> upstream :)
> What is the rationale for the AESS patches in Letux? Does Linux
> currently have no AESS support, or do these patches modify
> existing Linux AESS support? If the latter, are the AESS patches
> in Letux fixing bugs or adding features?

No, there is no AESS in kernel.org. Andrej did port an older
version written by Peter (CC:) and I made it work (well compile)
again on newer mainline kernels.

What is not working is firmware loading.

And there are bugs in the integration (API to setup DAI links etc.
has changed).

So we carry that code along in the hope that Peter or someone
else finds the time to fix the issues introduced by not having
it upstream.

> If the former (no existing AESS support in Linux), then does the
> hardware targeted by Letux not have audio capabilities
> (alternative to AESS) for which there is existing support in
> Linux?

Yes. Of course. Think of it as a coprocessor like a GPU.

Without AESS we can use the upstream twl6040 driver directly
and use it as a simple sound card through aplay. This is the
status you get if you use omap2plus_defconfig and/or build a
kernel for Pandaboard or OMAP5EVM.

But AESS has some nice features:
* can run independently of OMAP5
* allows to mix headset, modem audio, bluetooth microphone etc.
  i.e. between all McBSP interfaces
* audio filters

These features make it interesting to use. But: this needs a
binary blob (like GPU or WiFi chips), which is a no-go for FLOSS

BTW: the OMAP4 + twl6040 (PandaBoard) has the same AESS.


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