Linux/AM5728: Default muxmode pins values

Ilya Kravchuk

Part Number: AM5728

Tool/software: Linux

I'm trying to configure pin muxmodes via dts file for a custom board, based on sitara am5728.
In the datasheet notes, that default pin muxemodes are pointed in the RESET REL. MUXMODE column. This column has same values, which means "Driver off" pin state. As I understand, almost all pins are disabled after power is on.
But in the am57xx-beagle-x15.dts and am57xx-evm.dts files I've seen just only mmc pin multiplexing.
I can't understand, how other pins for periphery works without pinctrl assigments in the dts, if all default states set to the "Driver off"?

over 8 years ago

0 Pavel Botev over 8 years ago

TI__Guru**** 170625 points

Hi Ilya,

The ROM Code also make some pinmux, see TRM for details, ch33 Initialization

Regards,
Pavel

0 Pavel Botev over 8 years ago in reply to Pavel Botev

TI__Guru**** 170625 points

Seems like you refer to dts in linux kernel:

linux-kernel/arch/arm/boot/dts/am57xx-evm.dts

Note that u-boot also makes some pinmux (like ROM Code and kernel) and these pinmux settings are valid in user space (unless overwritten).

Regards,
Pavel

0 Ilya Kravchuk over 8 years ago in reply to Pavel Botev

Expert 1520 points

Thanks for fast reply.
And in addition, is in the linux user space some mechanism, which provide pin multiplexing functionality?

0 Pavel Botev over 8 years ago in reply to Ilya Kravchuk

TI__Guru**** 170625 points

Ilya,

Changing the pinmux from user space is not recommended, you will hit silicon errata i869.

All pinmux or IODelay configurations (with the exception of MMC) need to occur in isolation mode. However, as described in the "Isolation Requirements" section of the AM572x TRM: "when the IOs are isolated, code must execute only from internal RAM." This is because isolation mode impacts all IOs and the DDR will not be accessible. Therefore, isolation mode and pinmux configuration must be done at boot time. Run-time pinmux changes in the kernel are not supported.

Regards,
Pavel

0 Pavel Botev over 8 years ago in reply to Pavel Botev

TI__Guru**** 170625 points

We have pinmux tool also:

www.ti.com/.../pinmuxtool

Regards,
Pavel

0 Ilya Kravchuk over 8 years ago in reply to Pavel Botev

Expert 1520 points

Now everything is clear.
Thanks a lot for your help.

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Linux/AM5728: Default muxmode pins values