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authorBin Meng <bin.meng@windriver.com>2021-04-30 15:13:00 +0800
committerAlistair Francis <alistair.francis@wdc.com>2021-06-08 09:59:42 +1000
commit0147af69abb17a1ab5780821659c2e71d081c1e2 (patch)
tree2ffc6276f465dae8ac47c6ee1e5c734cbf772ba4 /docs
parent3ede8967c8a586c226da21d04283c72e24a2385e (diff)
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docs/system/riscv: sifive_u: Document '-dtb' usage
Update the 'sifive_u' machine documentation to mention the '-dtb' option that can be used to pass a custom DTB to QEMU. Signed-off-by: Bin Meng <bin.meng@windriver.com> Reviewed-by: Alistair Francis <alistair.francis@wdc.com> Message-id: 20210430071302.1489082-6-bmeng.cn@gmail.com Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Diffstat (limited to 'docs')
-rw-r--r--docs/system/riscv/sifive_u.rst47
1 files changed, 41 insertions, 6 deletions
diff --git a/docs/system/riscv/sifive_u.rst b/docs/system/riscv/sifive_u.rst
index dcdfbda..32d0a1b 100644
--- a/docs/system/riscv/sifive_u.rst
+++ b/docs/system/riscv/sifive_u.rst
@@ -36,12 +36,21 @@ Hardware configuration information
----------------------------------
The ``sifive_u`` machine automatically generates a device tree blob ("dtb")
-which it passes to the guest. This provides information about the addresses,
-interrupt lines and other configuration of the various devices in the system.
-Guest software should discover the devices that are present in the generated
-DTB instead of using a DTB for the real hardware, as some of the devices are
-not modeled by QEMU and trying to access these devices may cause unexpected
-behavior.
+which it passes to the guest, if there is no ``-dtb`` option. This provides
+information about the addresses, interrupt lines and other configuration of
+the various devices in the system. Guest software should discover the devices
+that are present in the generated DTB instead of using a DTB for the real
+hardware, as some of the devices are not modeled by QEMU and trying to access
+these devices may cause unexpected behavior.
+
+If users want to provide their own DTB, they can use the ``-dtb`` option.
+These DTBs should have the following requirements:
+
+* The /cpus node should contain at least one subnode for E51 and the number
+ of subnodes should match QEMU's ``-smp`` option
+* The /memory reg size should match QEMU’s selected ram_size via ``-m``
+* Should contain a node for the CLINT device with a compatible string
+ "riscv,clint0" if using with OpenSBI BIOS images
Boot options
------------
@@ -122,6 +131,32 @@ To boot the newly built Linux kernel in QEMU with the ``sifive_u`` machine:
-initrd /path/to/rootfs.ext4 \
-append "root=/dev/ram"
+Alternatively, we can use a custom DTB to boot the machine by inserting a CLINT
+node in fu540-c000.dtsi in the Linux kernel,
+
+.. code-block:: none
+
+ clint: clint@2000000 {
+ compatible = "riscv,clint0";
+ interrupts-extended = <&cpu0_intc 3 &cpu0_intc 7
+ &cpu1_intc 3 &cpu1_intc 7
+ &cpu2_intc 3 &cpu2_intc 7
+ &cpu3_intc 3 &cpu3_intc 7
+ &cpu4_intc 3 &cpu4_intc 7>;
+ reg = <0x00 0x2000000 0x00 0x10000>;
+ };
+
+with the following command line options:
+
+.. code-block:: bash
+
+ $ qemu-system-riscv64 -M sifive_u -smp 5 -m 8G \
+ -display none -serial stdio \
+ -kernel arch/riscv/boot/Image \
+ -dtb arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dtb \
+ -initrd /path/to/rootfs.ext4 \
+ -append "root=/dev/ram"
+
To build a Linux mainline kernel that can be booted by the ``sifive_u`` machine
in 32-bit mode, use the rv32_defconfig configuration. A patch is required to
fix the 32-bit boot issue for Linux kernel v5.10.