Intel SOF firmware

[Jaroslav Kysela]

Hi all,

   I would like you to introduce the situation with the Intel's Sound Open 
Firmware. We have finally a stable version of the driver in the Fedora kernel 
(5.5.7), so it's time to discuss this.

   The issue is that Intel need to deal with three type of files. The first 
file is the firmware (binary instruction blob which is executed in DSP, suffix 
.ri). The second file is the topology and configuration for the ALSA's ASoC 
core / SOF driver (suffix .tplg). Those both files are loaded via the firmware 
load calls from the kernel. The names for those files are determined using the 
hardware probe. The .ri files are platform (Broadwell etc.) dependent. The 
topology files might differ more (HDMI configuration, codec configuration etc.).

   The third file is not loaded via the firmware call, it contains the debug 
strings (SOF firmware is stripped, thus only pointers are returned through the 
trace interface and there's utility sof-logger which converts those pointers 
back to the strings using those .ldc files). It's just for the debugging 
purposes and for the normal operation, it is not used at all.

   The last piece is the signing. Intel has a secure mechanism which is 
activated in DSP, so DSP doesn't accept the unsigned firmware, if the hardware 
vendor wants (and they usually wants this security). So, although, the SOF 
firmware is being developed as open source, we cannot do own modifications, 
because we don't have the signing keys. Of course, there is open hardware 
where the public keys are used (like UP^2 or some Chromebooks). But Lenovo, 
Dell and others requires firmware signed by Intel.

   Personally, I'm trying to convince Intel's people to release the stable 
signed firmware files to linux-firmware, but so far, I have not been 
successful so far. My opinion is that the tested and verified binary topology 
files should belong to the linux-firmware, too. Intel do not agree on this 
(distributions should compile the topology binaries from the sources). 
Unfortunately, the topology sources are not distributed separately from the 
SOF firmware, so we need to deal with the whole SOF tree.

   For Fedora, I'm packaging the SOF firmware, topology and debug (.ldc) 
bundle (https://www.alsa-project.org/files/pub/misc/sof/) via the 
alsa-firmware package for now (this package is not installed by default which 
causes another bug iteration 'install this package' for users). Note that this 
is not in the upstream alsa-firmware tar ball. It's an extra thing.

   The last activity from the Intel is the sof-bin repository: 
https://github.com/thesofproject/sof-bin/tree/stable-v1.4.2 . It's probably a 
good step forward to have this reference, but it's outside the linux-firmware 
repository. I don't know if they want to mirror this to linux-firmware.

   The objective: Fedora/RHEL users should have sound available after the 
initial installation, thus we need to find the way to add those files to 
linux-firmware or install alsa-firmware package by default. Maybe, the best 
way will be to create another alsa-sof-bin package for the Intel's sof-bin 
releases and install it by default like iwl*-firmware files for their WiFi chips.

   I would like to hear your comments or proposals.

   Upstream discussions:

https://mailman.alsa-project.org/pipermail/sound-open-firmware/2020-Janua...
https://github.com/thesofproject/sof/issues/2200
https://github.com/thesofproject/sof-bin/pull/2 [Discussion]

				Thank you,
						Jaroslav

-- 
Jaroslav Kysela <jkysela(a)redhat.com&gt;
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.