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| author | Grant Likely <grant.likely@arm.com> | 2018-09-06 19:29:27 +0100 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2018-09-09 14:46:44 -0600 |
| commit | 9331e5e7b848edfced6b35547888eae913e3e189 (patch) | |
| tree | b7094b1bb308f5c6c2a7ab85c3073cc6fc80a697 /Documentation/efi-stub.txt | |
| parent | 2f4830ef96d21e144b742c394eb12888b0e233cc (diff) | |
| download | linux-9331e5e7b848edfced6b35547888eae913e3e189.tar.gz linux-9331e5e7b848edfced6b35547888eae913e3e189.tar.bz2 linux-9331e5e7b848edfced6b35547888eae913e3e189.zip | |
efi_stub: update documentation on dtb= parameter
The dtb= parameter is no longer the primary mechanism for providing a
devicetree to the kernel. Now either firmware or the boot selector (ex.
Grub) should provide the devicetree and dtb= should only be used for
debug or when using firmware that doesn't understand DT.
Update the EFI stub documentation to reflect the current usage.
Signed-off-by: Grant Likely <grant.likely@arm.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Acked-by: Leif Lindholm <leif.lindholm@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/efi-stub.txt')
| -rw-r--r-- | Documentation/efi-stub.txt | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/Documentation/efi-stub.txt b/Documentation/efi-stub.txt index 41df801f9a50..833edb0d0bc4 100644 --- a/Documentation/efi-stub.txt +++ b/Documentation/efi-stub.txt @@ -83,7 +83,18 @@ is passed to bzImage.efi. The "dtb=" option ----------------- -For the ARM and arm64 architectures, we also need to be able to provide a -device tree to the kernel. This is done with the "dtb=" command line option, -and is processed in the same manner as the "initrd=" option that is +For the ARM and arm64 architectures, a device tree must be provided to +the kernel. Normally firmware shall supply the device tree via the +EFI CONFIGURATION TABLE. However, the "dtb=" command line option can +be used to override the firmware supplied device tree, or to supply +one when firmware is unable to. + +Please note: Firmware adds runtime configuration information to the +device tree before booting the kernel. If dtb= is used to override +the device tree, then any runtime data provided by firmware will be +lost. The dtb= option should only be used either as a debug tool, or +as a last resort when a device tree is not provided in the EFI +CONFIGURATION TABLE. + +"dtb=" is processed in the same manner as the "initrd=" option that is described above. |