info needed on u-boot.imx dts files.

[prasannakulkarni]

Hi,

       We have tried porting of Android Oreo on our customized board(based on imx6dl). there was some changes related to UART muxing for our board, those related changes I have made in  "uboot-imx/board/freescale/mx6sabresd/mx6sabresd.c" .  we have built mfg u-boot placed in appropriate path flashed the images successfully. after that when we tried to boot board, UART was not working 4-5 days we have worked on that to resolve the issue.

      How come UART worked in mfg_u-boot and didn't work in actual android u-boot? After trying many things we found that android u-boot makes use of dts files which we need to modify UART muxing related changes here also !!!. It worked

after this change.

     My question is,  why nxp developers have kept muxing at both the places?

1. uboot-imx/board/freescale/mx6sabresd/mx6sabresd.c

2. uboot-imx/arch/arm/dts/imx6qdl-sabresd.dtsi

      There are no documents which tells about these information. By seeing "uboot-imx/board/freescale/mx6sabresd/mx6sabresd.c" board file and PIN muxing in that file also,  we had assumed that kernel onwards dts files are being used.

Our understanding is like this,

Is it so, mfg_u-boot.imx doesn't make use of dts

where as,  android u-boot.imx makes use of dts files?

Kindly update us.

[igorpadykov]

Hi  Prasanna

you did not provide info what version was used, so it makes sense to recheck

nxp official software documentation

i.MX Software | NXP 

As stated on below link, nxp documentation described usage of uboot dts files

Device Tree(DTS) in Uboot 

General info about uboot vs linux dts usage can be found on web:

arm - Why Device Tree Structure (DTS) file is needed both in bootloader and kernel source code? - St... 

Best regards
igor
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[prasannakulkarni]

Hi Igorpadykov , 

       Why pin muxing is done at two places in board file as well as in dts files... My basic question is still not answered.....

[igorpadykov]

it is answered on arm - Why Device Tree Structure (DTS) file is needed both in bootloader and kernel source code? - St... 

"The u-boot version allows different version of u-boot to run on several boards"

Best regards
igor

[prasannakulkarni]

Hi Igorpadykov ,

         I am not questioning about dts at kernel, in u-boot only why at two places the PIN muxing is done at boardfile as well as in dts file. here am not at all talking on kernel....  

1. About u-boot

                            Has board file and dts files of its own copy.

2. kernel

                             fully implemented FDT so no board file concept it has its own copy of dts files.

 Here am not at all questioning about kernel and its dts.

my question is simple why in uboot alone twice PIN muxing is done? in board file as well as in dts file. like kernel they would have only used dts alone in uboot also...

this creates ambiguity that two places I need to change muxing in uboot.

1. at board file of uboot

2. dts file of uboot.

Again am repeating about kernel and its dts am clear I dont have any doubts on kernel. my doubts are only with uboot.

[prasannakulkarni]

Hi,

    It is u- boot version 2017.x which is used along with imx6 Android O 8.0.0_1.0.0 release...