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There are a set of custom u-boot environmental variables used during boot, which either are set dynamically by custom u-boot commands, or are imported from an additional protected u-boot environment or are part of the regular SPI u-boot environment but are used to control the runtime behavior.
The PlutoSDR or M2k firmware (FIT image) supports multiple HW revisions. It’s being done reading a voltage divider which is unique for a given HW revision using the on chip XADC. This voltage is then mapped into 10 possible values which are then set in the fit_config
environmental variable. Values are in the form of config@%d
where %d is in the range from 0..9. This variable is then being used to load the corresponding FIT config which is right now only a dedicated device tree, however when necessary can be extended to also load a different bitfile.
The adi_hwref
command will set fit_config
and for Pulto Rev.A it will additionally set the PlutoRevA
variable.
variable | comment |
---|---|
fit_config | config@ number |
PlutoRevA | set only for Rev.A |
During factory calibration the onboard TCXO reference frequency is measured and the actual reference clock frequency is stored in an additional protected SPI environment which is imported during boot.
Later on this value is used to patch the device tree property clock-frequency
in the /clocks/clock@0
path.
This step can be skipped by the user when setting the ad936x_skip_ext_refclk
variable.
This allows for custom reference clock frequency set in the regular device tree.
variable | device tree destination | Comment |
---|---|---|
ad936x_ext_refclk | /clocks/clock@0 clock-frequency | Skip this by setting the ad936x_skip_ext_refclk variable |
model | /model | Model string |
attr_name | /amba/spi@e0006000/ad9361-phy@0 ${attr_name} ${attr_val} | |
attr_val | /amba/spi@e0006000/ad9361-phy@0 ${attr_name} ${attr_val} |
The DFU altsetting of the DFU interface is stored in the dfu_alt_num
variable and the transfers size is stored in the filesize
variable.
variable | comment |
---|---|
dfu_alt_num | altsetting of the DFU interface in progress |
filesize | filesize of the transferred firmware image |
variable | comment |
---|---|
uboot-version | u-boot version string set by the envversion command |