2
0
mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-25 05:34:00 +08:00
linux-next/Documentation/devicetree/bindings/chosen.txt
Scott Wood 567cf94dc7 powerpc/book3e-64/kexec: Enable SMP release
The SMP release mechanism for FSL book3e is different from when booting
with normal hardware.  In theory we could simulate the normal spin
table mechanism, but not at the addresses U-Boot put in the device tree
-- so there'd need to be even more communication between the kernel and
kexec to set that up.  Instead, kexec-tools will set a boolean property
linux,booted-from-kexec in the /chosen node.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: devicetree@vger.kernel.org
2015-10-27 18:13:29 -05:00

55 lines
1.6 KiB
Plaintext

The chosen node
---------------
The chosen node does not represent a real device, but serves as a place
for passing data between firmware and the operating system, like boot
arguments. Data in the chosen node does not represent the hardware.
stdout-path property
--------------------
Device trees may specify the device to be used for boot console output
with a stdout-path property under /chosen, as described in ePAPR, e.g.
/ {
chosen {
stdout-path = "/serial@f00:115200";
};
serial@f00 {
compatible = "vendor,some-uart";
reg = <0xf00 0x10>;
};
};
If the character ":" is present in the value, this terminates the path.
The meaning of any characters following the ":" is device-specific, and
must be specified in the relevant binding documentation.
For UART devices, the preferred binding is a string in the form:
<baud>{<parity>{<bits>{<flow>}}}
where
baud - baud rate in decimal
parity - 'n' (none), 'o', (odd) or 'e' (even)
bits - number of data bits
flow - 'r' (rts)
For example: 115200n8r
Implementation note: Linux will look for the property "linux,stdout-path" or
on PowerPC "stdout" if "stdout-path" is not found. However, the
"linux,stdout-path" and "stdout" properties are deprecated. New platforms
should only use the "stdout-path" property.
linux,booted-from-kexec
-----------------------
This property is set (currently only on PowerPC, and only needed on
book3e) by some versions of kexec-tools to tell the new kernel that it
is being booted by kexec, as the booting environment may differ (e.g.
a different secondary CPU release mechanism)