Merge tag 'pull-or1k-20220904' of https://github.com/stffrdhrn/qemu into staging

OpenRISC updates for 7.2.0

Updates to add the OpenRISC virt plaform to QEMU. Highlights
include:

- New virt plaform with, virtio and pci bus support
- OpenRISC support for MTTCG
- Goldfish RTC device endianness is configurable now

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* tag 'pull-or1k-20220904' of https://github.com/stffrdhrn/qemu:
  docs/system: openrisc: Add OpenRISC documentation
  hw/openrisc: virt: pass random seed to fdt
  target/openrisc: Interrupt handling fixes
  target/openrisc: Enable MTTCG
  target/openrisc: Add interrupted CPU to log
  hw/openrisc: Initialize timer time at startup
  hw/openrisc: Add PCI bus support to virt
  hw/openrisc: Add the OpenRISC virtual machine
  goldfish_rtc: Add big-endian property
  target/openrisc: Fix memory reading in debugger
  hw/openrisc: Split re-usable boot time apis out to boot.c

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/docs/system/target-openrisc.rst b/docs/system/target-openrisc.rst
new file mode 100644
index 0000000000..22cb2217a6
--- /dev/null
+++ b/docs/system/target-openrisc.rst
@@ -0,0 +1,71 @@
+.. _OpenRISC-System-emulator:
+
+OpenRISC System emulator
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+QEMU can emulate 32-bit OpenRISC CPUs using the ``qemu-system-or1k`` executable.
+
+OpenRISC CPUs are generally built into "system-on-chip" (SoC) designs that run
+on FPGAs.  These SoCs are based on the same core architecture as the or1ksim
+(the original OpenRISC instruction level simulator) which QEMU supports. For
+this reason QEMU does not need to support many different boards to support the
+OpenRISC hardware ecosystem.
+
+The OpenRISC CPU supported by QEMU is the ``or1200``, it supports an MMU and can
+run linux.
+
+Choosing a board model
+======================
+
+For QEMU's OpenRISC system emulation, you must specify which board model you
+want to use with the ``-M`` or ``--machine`` option; the default machine is
+``or1k-sim``.
+
+If you intend to boot Linux, it is possible to have a single kernel image that
+will boot on any of the QEMU machines. To do this one would compile all required
+drivers into the kernel. This is possible because QEMU will create a device tree
+structure that describes the QEMU machine and pass a pointer to the structure to
+the kernel.  The kernel can then use this to configure itself for the machine.
+
+However, typically users will have specific firmware images for a specific machine.
+
+If you already have a system image or a kernel that works on hardware and you
+want to boot with QEMU, check whether QEMU lists that machine in its ``-machine
+help`` output. If it is listed, then you can probably use that board model. If
+it is not listed, then unfortunately your image will almost certainly not boot
+on QEMU. (You might be able to extract the filesystem and use that with a
+different kernel which boots on a system that QEMU does emulate.)
+
+If you don't care about reproducing the idiosyncrasies of a particular
+bit of hardware, such as small amount of RAM, no PCI or other hard disk, etc.,
+and just want to run Linux, the best option is to use the ``virt`` board. This
+is a platform which doesn't correspond to any real hardware and is designed for
+use in virtual machines. You'll need to compile Linux with a suitable
+configuration for running on the ``virt`` board. ``virt`` supports PCI, virtio
+and large amounts of RAM.
+
+Board-specific documentation
+============================
+
+..
+   This table of contents should be kept sorted alphabetically
+   by the title text of each file, which isn't the same ordering
+   as an alphabetical sort by filename.
+
+.. toctree::
+   :maxdepth: 1
+
+   openrisc/or1k-sim
+   openrisc/virt
+
+Emulated CPU architecture support
+=================================
+
+.. toctree::
+   openrisc/emulation
+
+OpenRISC CPU features
+=====================
+
+.. toctree::
+   openrisc/cpu-features