Noise while booting armstoneA9r3

    Dear support team,


    on our armstoneA9r3 sample with Buildroot fsimx6-B2022.10 release we have the effect/problem of some noise on the Audio Line Out while loading the kernel until the audio output is initialized. Can someone confirm that effect? If yes, what do we need to change in the device tree or in u-boot to initialize the Audio Line Out pins to silence while booting?


    Thanks in advance

    RS

    Hello,


    we can reproduce the issue if we play a sound in Linux and reboot.

    We than here a frequent noise starting from Uboot until the SGTL driver loads.

    The issue does not occur from a cold start.


    Is this correct?


    We will have to further investigate on this.


    Your F&S Support Team

    Yes, I tested and you are right (it's also new to me). On a cold start this effect does not occur only after software reboot. But that's also a problem for us, because our customers create projects for our devices and every time they load the projects, the device reboots.


    Kind regards

    Hello,


    we have further investigated the issue and a Hotfix would be to mute the Lineout before rebooting

    amixer sset 'Lineout' mute

    reboot


    We will create a patch that will do this automatically when unloading the driver.

    This however will not fix the issue if the Board is resetted by a Hardware reset.

    We will have to further investigate this.


    Your F&S Support Team