Linux/DRA756: Using only UART3 for serial in u-boot

Tonu Zalpure

Part Number: DRA756

Tool/software: Linux

Hi All,

We have a Custom Board based on J6 EVK/DRA7xx SOC, We have only UART3 available for serial and no provision to set it via switch settings.

In u-boot 2016.05 we are trying to figure out code changes which disables reading switch settings and hard code UART3 as the only serial option.

We have done following changes :

Files changed:

1) include/configs/dra7xx_evm.h

2) arch/arm/include/asm/arch-omap5/mux_dra7xx.h

3) board/ti/dra7xx/mux_data.h

Code changes:

#define CONFIG_CONS_INDEX 3

#define CONFIG_SYS_NS16550_COM3 UART3_BASE

After this we expect only UART3 to work but getting u-boot logs with both ON/OFF settings on SW5 pin 5.

Regards,

Tonu Zalpure

BlackPepper Technologies

over 8 years ago

0 Yordan Kamenov over 8 years ago

TI__Mastermind 42515 points

Hi Tonu,

can you try to change in "arch/arm/dts/dra7-evm-common.dtsi" (or the correct .dts you use for your board) this:

chosen {
stdout-path = &uart1;
tick-timer = &timer2;
};

to this:

chosen {
stdout-path = &uart3;
tick-timer = &timer2;
};

Regards,
Yordan

0 Tonu Zalpure over 8 years ago in reply to Yordan Kamenov

Intellectual 320 points

Thanks Yordan,

That resolves the issue.

Regards,
Tonu

0 Tonu Zalpure over 8 years ago in reply to Yordan Kamenov

Intellectual 320 points

Hi Yordan,

Is there any way to select only UART1 now instead of UART3 .
If there is any wiki link or document, could you please share?

Thanks,
Tonu

0 Yordan Kamenov over 8 years ago in reply to Tonu Zalpure

TI__Mastermind 42515 points

Hi Tonu,

I have pinged an expert to help further.

Regards,
Yordan

0 Shravan Karthik over 8 years ago in reply to Yordan Kamenov

TI__Genius 14650 points

Hi Tonu,

Just to be clear, with the changes suggested previously, you could get the logs on UART-3 correct?
By default UART-1 is used, so if I understand your use-case correctly, you wouldn't need to make any changes.

Regards
Shravan

0 Tonu Zalpure over 8 years ago in reply to Shravan Karthik

Intellectual 320 points

Hi Shravan,

Yes, I could configure just to get logs only on UART-3.

We have a custom board where there is no switch to select UART1/3.
We can only use UART-1 as serial(correction from yesterday information*).

Currently we are trying experiments on EVM where we want to:
1. make this code changes to hard code only UART-1 and there should be no logs on UART-3
2.Disable code which reads this switch setting as we don't have any

Any Direct/Indirect Inputs over this will be valuable.

Thanks,
Tonu

0 Shravan Karthik over 8 years ago in reply to Tonu Zalpure

TI__Genius 14650 points

Hi Tonu,

Can you please provide the changes you've made? Also can you attach the your u-boot config file (.config file in the u-boot repo).

If you revert to the default configuration, the serial logs will be output on UART-1, since by default UART-1 is used on DRA75x. In your config file CONFIG_CONS_INDEX must be 1.

We don't have any code that reads switch setting to and selects between UART-1 and UART-3 -- both can be used independently.

Regards

Shravan

0 Tonu Zalpure over 8 years ago in reply to Shravan Karthik

Intellectual 320 points

Hi Shravan,

Thanks for your inputs.It has clarified lot of our doubts.

Yes ,in default config file CONFIG_CONS_INDEX is 1.
As UART-1 is default , I understand we won't any further changes in code to get it working.

Thanks for clarifying that there is no code which reads switch settings selects between UART-1 and UART-3.
So, SW 5 pin 5 toggle should not make any difference? Then is there any way to confirm which UART-1/3 is being used for logs?

Also I would like to keep this thread open for next few days until we try these experiments on custom board and get UART working.If any inputs/clarification required will update here.

Thanks,
Tonu

0 Shravan Karthik over 8 years ago in reply to Tonu Zalpure

TI__Genius 14650 points

Hi Tonu,

I'm not sure about the mux configuration at your end, however unless you're toggling the mux configuration for UART-1, it should work. To ensure UART-1 is used disable UART-3 from the device-tree.

As requested, I shall keep the thread open.

Regards

Shravan

0 Tonu Zalpure over 8 years ago in reply to Shravan Karthik

Intellectual 320 points

Hi Shravan,Yordan,

UART on Custom board is up,
Thanks for all the support.
We can close this thread.

Regards,
Tonu

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Linux/DRA756: Using only UART3 for serial in u-boot