util: Add scripts to recreate amdgpu ROM and MMIOs

Although the binary ROM blob and MMIO trace will be placed in
gem5-resources later as 'golden' versions, the scripts are added to
provide instructions for power users of Full System amdgpu that may want
to recreate the files themselves or use a GPU other than the Vega10 GPU
currently modeled.

Change-Id: Ica7ef3b9820b30be32a148ce6cf1d2f81dc2adf9
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/46162
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>

util/amdgpu/fs_files/README.md

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+The utility scripts provided in this directly can be used to recreate the
+files needed to run Full System amdgpu. Golden versions of these files are
+provided in the gem5-resources repository.
+
+These scripts are intended to be run on a Linux system with a discrete AMD
+GPU card running the same kernel version as the disk image which will be used
+for Full System simulations. To ensure the kernel versions match, it is
+recommended that the user uses the `dd` utility to make a copy of the disk
+image to a secondary physical disk and then boot from that disk image.
+
+# MMIO Trace collection
+
+The script `collect_mmio_trace.sh` collects an MMIO trace. For this to work,
+MMIO tracing must be enabled in the kernel. Using the disk image approach
+above and/or using recent kernel versions based on Ubuntu, this is enabled
+by default.
+
+Before collecting the trace, the amdgpu module must be blacklisted such that
+we can enable tracing before the modprobe occurs and disabled once modprobe
+is complete.
+
+This can be done using either:
+    `echo 'blacklist amdgpu' >> /etc/modprobe.d/blacklist.conf`
+or
+    add `modprobe.blacklist=amdgpu` to kernel boot command (e.g., in grub)
+And then reboot.
+
+The script will take care of the proper options and run the mmiotrace
+commands. The output trace will likely contain unrelated from other MMIOs
+and therefore will be around 500MB in size. You will want to reboot again
+as mmiotrace disables SMP.
+
+# GPU ROM Dump
+
+The script `dump_gpu_rom.sh` dumps the GPU ROM. The GPU ROM on x86 resides
+in the memory range 0xC0000 - 0xDFFFF. The script simply uses the `dd`
+command to copy this range from /dev/mem. The amdgpu driver must be loaded
+in order for the ROM to be written to this region, so run `modprobe` first.