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

H. Nikolaus Schaller hns at goldelico.com
Tue Jul 30 17:45:45 CEST 2019

> Am 30.07.2019 um 17:41 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> Some additional thoughts:
> * here is the "Issue" record: http://projects.goldelico.com/p/gta04-kernel/issues/883/
> * the letux/pyra-minimal branch is without any AESS patch (on top of 5.3-rc2).
>  I tried audio yesterday on the Pyra but did not get more than scratchy noise :(
> * There was a really good description on omappedia but I think it has gone.

I think I have found it: http://omappedia.org/wiki/Audio_Drive_Arch#Audio_Back_End_.28ABE.29

"AESS" is also called "ABE" in other contexts. Somehow confusing.

ABE = Audio Back End (= inside OMAP4/5) - Audio Front End = twl6040 + speakers or other sound sources
AESS = Audio Engine Sub-system (is part of ABE).

> * I think the Droid 4 is omap4430 + twl6040 + telephony modem and therefore the
> developers may also be interested in this.
>> Am 30.07.2019 um 17:21 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
>> Hi,
>>> 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 been replaced by pointers to other structs.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
>> purists.
>> BTW: the OMAP4 + twl6040 (PandaBoard) has the same AESS.
>> BR,
>> Nikolaus
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