U-Boot support board detection at run time and based on it change DT.
This feature is implemented for SOM Kria platforms which contain two
eeproms which contain information about SOM module and CC (Carrier card).
Full U-Boot starts with minimal DT file defined by
CONFIG_DEFAULT_DEVICE_TREE which is available in multi DTB fit image.
It is using default setup of board_name variable initializaed to
DEVICE_TREE which corresponds to CONFIG_DEFAULT_DEVICE_TREE option.
When DTB_RESELECT is enabled board_detection() is called. Keep it your mind
that this code is called before relocation. board_detection() is calling
xilinx_read_eeprom() which fills board_info (xilinx_board_description)
structure which are parsed in board_name_decode().
Based on DT configuration and amount of nvmemX aliases name of the board is
composed by concatenating CONFIG_SYS_BOARD "-" <board_name> "-rev"
<board_revision> "-" <cc_name> "-rev" <cc_revision>.
If CC is not present or more are available it keeps going.
When board name is composed and returned from board_name_decode() it is
assigned to board_name variable which is used by
board_fit_config_name_match() which is called via fdtdec_setup() when it
goes over config options in multi dtb FIT image.
From practical point of view multi DTB image is key point here which has to
contain configs for detected combinations. Unfortunately as of now they
have to be full DTBs and DTBOs are not supported.
That's why configuration like:
config_X {
description = "zynqmp-board-cc";
fdt = "board", "cc";
};
needs to be squashed together with:
fdtoverlay -o zynqmp-board-cc -i arch/arm/dts/zynqmp-board.dtb \
arch/arm/dts/zynqmp-cc.dtbo
and only one dtb is in fit:
config_X {
description = "zynqmp-board-cc";
fdt = "board-cc";
};
For creating multi DTBs fit image use mkimage -E, e.g.:
mkimage -E -f all.its all.dtb
When DTB_RESELECT is enabled xilinx_read_eeprom() is called before
relocation and it uses calloc for getting a buffer. Because this is dynamic
memory it is not relocated that's why xilinx_read_eeprom() is called again
as the part of board_init(). This second read with calloc buffer placed in
proper position board_late_init_xilinx() can setup u-boot variables as
before.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
DT files have been added this year but forgot to update it that's why do it
in separate patch now.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
It is not recommended to have aliases for gpio. In past it was used in
Linux for assigning numbers via sysfs which is deprecated and libgpiod
should be used instead.
In U-Boot this number is used for seq number but gpio offset are not
counted from this number. That's why having these aliases only for seq
number is not needed. As is done in Linux it is the best to use full gpio
name instead of sequence number which depends on sequence in binding.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
The patch contains several DT files for SOM platform.
Carrier card is sck-kv (KV260) revA/B. SMK-K26 is description for starter
kit which doesn't have EMMC populated. And SM-K26 is full som with EMMC.
Files are divided in this way to make sure that SOM can be plugged to
different carrier card and all peripherals on SOM (or defined by a spec) can
be used by U-Boot. Full DT for SOM+CC can be merged together as overlays.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
