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[03/16] riscv: qemu: Explain how to extract the generate devicetree

Message ID 20211013010120.96851-4-sjg@chromium.org
State New
Headers show
Series fdt: Make OF_BOARD a boolean option | expand

Commit Message

Simon Glass Oct. 13, 2021, 1:01 a.m. UTC 
QEMU currently generates a devicetree for use with U-Boot. Explain how to
obtain it.

Signed-off-by: Simon Glass <sjg@chromium.org>
---

 doc/board/emulation/qemu-riscv.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)
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Patch

diff --git a/doc/board/emulation/qemu-riscv.rst b/doc/board/emulation/qemu-riscv.rst
index 4b8e104a215..b3cf7085847 100644
--- a/doc/board/emulation/qemu-riscv.rst
+++ b/doc/board/emulation/qemu-riscv.rst
@@ -113,3 +113,15 @@  An attached disk can be emulated by adding::
     -device ide-hd,drive=mydisk,bus=ahci.0
 
 You will have to run 'scsi scan' to use it.
+
+Obtaining the QEMU devicetree
+-----------------------------
+
+QEMU generates its own devicetree to pass to U-Boot and does this by default.
+You can use `-dtb u-boot.dtb` to force QEMU to use U-Boot's in-tree version.
+
+To obtain the devicetree that qemu generates, add `-machine dumpdtb=dtb.dtb`,
+e.g.::
+
+    qemu-system-riscv64 -nographic -machine virt -bios u-boot \
+	    -machine dumpdtb=dtb.dtb