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authorTomaz Solc <tomaz.solc@tablix.org>2019-02-27 14:22:15 +0100
committerSascha Hauer <s.hauer@pengutronix.de>2019-03-04 08:48:15 +0100
commit67e38cdac3e94b3a3f6aa38a539073e659fea52c (patch)
tree607db5316d6df5f504d0905f3fa5172eb212380d /Documentation
parente390c8799d914bc4ef84c934b7875078489c26ab (diff)
downloadbarebox-67e38cdac3e94b3a3f6aa38a539073e659fea52c.tar.gz
ARM: rpi: save bootargs from VC FDT to vc.bootargs
When booting a Raspberry Pi, it is useful to extract bootargs from the device tree that was created by the VideoCore firmware. These bootargs contain for example settings for the framebuffer that the kernel needs to properly set the video output. This commit extracts the bootargs in the board initialization code and saves them to the vc.bootargs global variable. For example, a bootloader environment can then add the contents of this variable to linux.bootargs.vc, which then gets included into the final bootargs for the kernel using CONFIG_FLEXIBLE_BOOTARGS. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/boards/bcm2835.rst6
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/boards/bcm2835.rst b/Documentation/boards/bcm2835.rst
index 95e9108..e9ad1d4 100644
--- a/Documentation/boards/bcm2835.rst
+++ b/Documentation/boards/bcm2835.rst
@@ -34,5 +34,11 @@ VideoCore firmware creates a device tree based on the entries in ``config.txt``.
bootm -o /vc.dtb /boot/kernel7.img
+VideoCore device tree also contains the kernel command-line that is constructed from ``cmdline.txt`` and other parameters internally determined by the VideoCore firmware. Normally in Barebox this command-line gets overwritten on boot by the Linux bootargs (see :ref:`booting_linux`).
+
+The original command-line from VideoCore device tree is available to the Barebox environment in the ``vc.bootargs`` global variable. For example, to append it to the Linux bootargs::
+
+ global linux.bootargs.vc="$global.vc.bootargs"
+
.. _Raspberry Pi firmware: https://codeload.github.com/raspberrypi/firmware/zip/80e1fbeb78f9df06701d28c0ed3a3060a3f557ef
.. _documentation for config.txt: https://www.raspberrypi.org/documentation/configuration/config-txt/