blob: c96b8f7109053e21edca880f580c21bbdd325946 [file] [log] [blame]
Mugunthan V Nc8336972016-01-16 21:33:58 +05301The chosen node
2---------------
3The chosen node does not represent a real device, but serves as a place
4for passing data like which serial device to used to print the logs etc
5
6
7stdout-path property
8--------------------
9Device trees may specify the device to be used for boot console output
10with a stdout-path property under /chosen.
11
12Example
13-------
14/ {
15 chosen {
16 stdout-path = "/serial@f00:115200";
17 };
18
19 serial@f00 {
20 compatible = "vendor,some-uart";
21 reg = <0xf00 0x10>;
22 };
23};
24
25tick-timer property
26-------------------
27In a system there are multiple timers, specify which timer to be used
28as the tick-timer. Earlier it was hardcoded in the timer driver now
29since device tree has all the timer nodes. Specify which timer to be
30used as tick timer.
31
32Example
33-------
34/ {
35 chosen {
36 tick-timer = "/timer2@f00";
37 };
38
39 timer2@f00 {
40 compatible = "vendor,some-timer";
41 reg = <0xf00 0x10>;
42 };
43};
Philipp Tomsichd02d11f2017-03-28 11:03:00 +020044
45u-boot,spl-boot-order property
46------------------------------
47
48In a system using an SPL stage and having multiple boot sources
49(e.g. SPI NOR flash, on-board eMMC and a removable SD-card), the boot
50device may be probed by reading the image and verifying an image
51signature.
52
53If the SPL is configured through the device-tree, the boot-order can
54be configured with the spl-boot-order property under the /chosen node.
55Each list element of the property should specify a device to be probed
56in the order they are listed: references (i.e. implicit paths), a full
57path or an alias is expected for each entry.
58
Philipp Tomsich80e9f882017-09-29 19:27:57 +020059A special specifier "same-as-spl" can be used at any position in the
60boot-order to direct U-Boot to insert the device the SPL was booted
61from there. Whether this is indeed inserted or silently ignored (if
62it is not supported on any given SoC/board or if the boot-device is
63not available to continue booting from) is implementation-defined.
64Note that if "same-as-spl" expands to an actual node for a given
65board, the corresponding node may appear multiple times in the
66boot-order (as there currently exists no mechanism to suppress
67duplicates from the list).
68
Philipp Tomsichd02d11f2017-03-28 11:03:00 +020069Example
70-------
71/ {
72 chosen {
Philipp Tomsich80e9f882017-09-29 19:27:57 +020073 u-boot,spl-boot-order = "same-as-spl", &sdmmc, "/sdhci@fe330000";
Philipp Tomsichd02d11f2017-03-28 11:03:00 +020074 };
75};