Xilinx Machines
===============

Xilinx uses an inheritence model to define defaults in a heirarchical
model.  This allows for machines to include other machines and then
override defaults.

For example, a carrier board with a system on module using a zynqmp ev
can be implements as:

k26_kv -> k26 -> zynqmp-ev-generic -> zynqmp-generic

The above needs to result MACHINEOVERRIDES and PACKAGE_ARCHS that include
all 4 machines.  To accomplish this, each machine.conf file should contain
the following preamble and postamble.

#### Preamble
MACHINEOVERRIDES =. "${@['', '<machine>:']['<machine>' != '${MACHINE}']}"
#### Regular settings follow


#### No additional settings should be after the Postamble
#### Postamble
PACKAGE_EXTRA_ARCHS:append = "${@['', ' <machine_arch>']['<machine>' != "${MACHINE}"]}"


Typically the first thing after the preamble will be a requires of the machine
configuration that we depend on.  After the machine would be changes to various
defaults.  The exception is when a different microblaze tune and/or defaulttune
is desired; these must be set before require of the inherited machine.

Typical case example (my-example.conf):

#### Preamble
MACHINEOVERRIDES =. "${@['', 'my-example:']['my-example' != '${MACHINE}']}"
#### Regular settings follow

require conf/machine/zynqmp-ev-generic.conf

HDF_MACHINE = "zcu102-zynqmp"
MACHINE_FEATURES += "pci"

#### No additional settings should be after the Postamble
#### Postamble
PACKAGE_EXTRA_ARCHS:append = "${@['', ' my_example']['my-example' != "${MACHINE}"]}"


Example of defaulttune override:

#### Preamble
MACHINEOVERRIDES =. "${@['', 'my-example:']['my-example' != '${MACHINE}']}"
#### Regular settings follow

DEFAULTTUNE = "aarch64"

require conf/machine/zynqmp-ev-generic.conf

HDF_MACHINE = "zcu102-zynqmp"
MACHINE_FEATURES += "pci"

#### No additional settings should be after the Postamble
#### Postamble
PACKAGE_EXTRA_ARCHS:append = "${@['', ' my_example']['my-example' != "${MACHINE}"]}"


Example of microblaze tune override:

#### Preamble
MACHINEOVERRIDES =. "${@['', 'my-example:']['my-example' != '${MACHINE}']}"
#### Regular settings follow

TUNE_FEATURES:tune-microblaze ?= "microblaze v8.50 barrel-shift reorder pattern-compare divide-hard multiply-high fpu-hard"

require conf/machine/microblaze-generic.conf

HDF_MACHINE = "ml605"
SERIAL_CONSOLE = "115200,ttyUL0"

#### No additional settings should be after the Postamble
#### Postamble
PACKAGE_EXTRA_ARCHS:append = "${@['', ' my_example']['my-example' != "${MACHINE}"]}"