Re: [Alsa-user] Firewire Audio Setting RME FF400 into Ubuntu 20.10

[Takashi S. <o-t...@sa...>]

Hi,

On Mon, Nov 30, 2020 at 09:22:13PM +0000, Riccardo Wanke via Alsa-user wrote:
> I try to compile my kernel adding the ieee1394 drivers and all other
> possible things that may help (adding the CONFIG_SND_FIREFACE).

In Ubuntu distribution, the package named as 'linux-modules-extra' includes
kernel modules relevant to Linux FireWire subsystem. For example of
5.7.0-15-generic kernel:
https://packages.ubuntu.com/groovy/amd64/linux-modules-extra-5.7.0-15-generic/filelist

> I know that I may use FFADO, but actually the things seems to be more
> complicated: the problem seems actually the connection that does not
> work properly (with the use of two adapters).

As long as I experienced, in Linux system, launching interrupt handler
triggered by peripherals on PCI-Express bus via PCI-Express protocol in
Thunderbolt 3 bus includes large jitter. I guess that Linux driver for
Thunderbolt chipset uses spin-locks carelessly and CPU waits release of
the spin-lock with IRQ-disabled state, but I didn't investigate further
because current my focus is on protocol implementation for audio and
music units on IEEE 1394 bus.

Anyway it's required to have extra care of the jitter so that any driver
processes content of isochronous packet of IEEE 1394 within interval of
interrupt scheduled by the driver via 1394 OHCI.


Regards

Takashi Sakamoto