[PATCH 02/13] arm: imx: Remove unused CONFIG_xxx_TAG support

[Fabio Estevam]

Hi Tom,

[Adding Bryan]

On Thu, Feb 4, 2021 at 12:49 AM Tom Rini <trini at konsulko.com> wrote:

> CONFIG_SERIAL_TAG is only used to configure the ATAG serial record.  It
> does nothing else.  On i.MX8* this is already being discarded.  On i.MX7
> we see things like:
>             warp7          : all -144 rodata +32 text -176
>                u-boot: add: 0/-2, grow: 0/-2 bytes: 0/-160 (-160)
>                  function                                   old     new   delta
>                  params                                       4       -      -4
>                  get_board_serial                            20       -     -20
>                  board_late_init                             96      56     -40
>                  boot_prep_linux                            156      60     -96

But then it will remove the support of reading serial number via fuses
which was added by:

commit 852cc548b3fdf6d5b46e2a96f876d14608ccdcf4
Author: Bryan O'Donoghue <bryan.odonoghue at linaro.org>
Date:   Mon Mar 26 15:27:34 2018 +0100

    warp7: Set u-boot serial# based on OTP value

    u-boot has a standard "serial#" environment variable that is suitable
    for storing the iSerial number we will supply via the USB device
    descriptor. serial# is automatically picked up by the disk subsystem in
    u-boot - thus providing a handy unique identifier in /dev/disk/by-id as
    detailed below.

    Storing the hardware serial identifier in serial# means we can change the
    serial# if we want before USB enumeration - thus making iSerial automatic
    via OTP but overridable if necessary.

    This patch reads the defined OTP fuse and sets environment variable
    "serial#" to the value read.

    With this patch in place the USB mass storage device will appear in
    /dev/disk/by-id with a unique name based on the OTP value. For example

    /dev/disk/by-id/usb-Linux_UMS_disk_0_WaRP7-0xf42400d3000001d4-0:0

    Signed-off-by: Bryan O'Donoghue <bryan.odonoghue at linaro.org>
    Cc: Fabio Estevam <fabio.estevam at nxp.com>
    Cc: Rui Miguel Silva <rui.silva at linaro.org>
    Cc: Ryan Harkin <ryan.harkin at linaro.org>
    Reviewed-by: Fabio Estevam <fabio.estevam at nxp.com>

> Currently, yes.  Historically ever?  Or even if so, you're OK just removing all
> of that code as well?  Thanks.

mx5 and mx6 used to boot board files in the past (NXP kernel 2.6.35
for mx5 or 3.0.x for mx6).

Such kernels are not even maintained by the NXP, so we should not
worry about booting non-DT with i.MX.