projects / people / ms / u-boot.git / blame
| Commit | Line | Data |
|---|---|---|
| c8336975 M |
1 | The chosen node |
| 2 | --------------- | |
| 3 | The chosen node does not represent a real device, but serves as a place | |
| 4 | for passing data like which serial device to used to print the logs etc | |
| 5 | ||
| 6 | ||
| 7 | stdout-path property | |
| 8 | -------------------- | |
| 9 | Device trees may specify the device to be used for boot console output | |
| 10 | with a stdout-path property under /chosen. | |
| 11 | ||
| 12 | Example | |
| 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 | ||
| 25 | tick-timer property | |
| 26 | ------------------- | |
| 27 | In a system there are multiple timers, specify which timer to be used | |
| 28 | as the tick-timer. Earlier it was hardcoded in the timer driver now | |
| 29 | since device tree has all the timer nodes. Specify which timer to be | |
| 30 | used as tick timer. | |
| 31 | ||
| 32 | Example | |
| 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 | }; | |
| d02d11f8 PT |
44 | |
| 45 | u-boot,spl-boot-order property | |
| 46 | ------------------------------ | |
| 47 | ||
| 48 | In 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 | |
| 50 | device may be probed by reading the image and verifying an image | |
| 51 | signature. | |
| 52 | ||
| 53 | If the SPL is configured through the device-tree, the boot-order can | |
| 54 | be configured with the spl-boot-order property under the /chosen node. | |
| 55 | Each list element of the property should specify a device to be probed | |
| 56 | in the order they are listed: references (i.e. implicit paths), a full | |
| 57 | path or an alias is expected for each entry. | |
| 58 | ||
| 80e9f88e PT |
59 | A special specifier "same-as-spl" can be used at any position in the |
| 60 | boot-order to direct U-Boot to insert the device the SPL was booted | |
| 61 | from there. Whether this is indeed inserted or silently ignored (if | |
| 62 | it is not supported on any given SoC/board or if the boot-device is | |
| 63 | not available to continue booting from) is implementation-defined. | |
| 64 | Note that if "same-as-spl" expands to an actual node for a given | |
| 65 | board, the corresponding node may appear multiple times in the | |
| 66 | boot-order (as there currently exists no mechanism to suppress | |
| 67 | duplicates from the list). | |
| 68 | ||
| d02d11f8 PT |
69 | Example |
| 70 | ------- | |
| 71 | / { | |
| 72 | chosen { | |
| 80e9f88e | 73 | u-boot,spl-boot-order = "same-as-spl", &sdmmc, "/sdhci@fe330000"; |
| d02d11f8 PT |
74 | }; |
| 75 | }; |