In the source for L4T (r21.4 in this case) for TK1, there are two folders under sound/soc/ - tegra and tegra-alt.
Judging by DTS compatible tags, tegra-alt appears to be the one to use with the K1 SoC.
I have some questions:
Is it correct that tegra-alt contains the drivers intended to be used with a K1 based system?
What is the reason for the fork? I can’t see any concrete reason myself that the ASoC drivers have been split into two, and some context on why this is the case would be helpful.
Actually if you look at the arch/arm/configs/tegra21_defconfig which is used to build the kernel, you will see it is using CONFIG_SND_SOC_TEGRA which is the sound/soc/tegra driver and not the ‘alt’ variant.
Essentially the ‘alt’ variant implements the various sound drivers (i2s, dmic, etc) as codecs and this provides more flexibility with routing audio through the audio crossbar dynamically from userspace and adding mixer controls to control certain features for the different drivers. For L4T on Tegra210 onwards we use the ‘alt’ sound driver variant.