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[Qemu-devel] [Bug 1826827] Re: dtc crash; pnv_dt_serial cannot find lpc'
[Qemu-devel] [Bug 1826827] Re: dtc crash; pnv_dt_serial cannot find lpc's phandle
Thu, 04 Jul 2019 03:25:53 -0000
This assertion should be fixed by upstream commit 8f695676227 "Avoid
assertion in check_interrupts_property()". That should be included in
dtc v1.5.1 which I hope to release soon.
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dtc crash; pnv_dt_serial cannot find lpc's phandle
Status in QEMU:
QEMU emulator version 4.0.50 (v4.0.0-142-ge0fb2c3d89)
Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers
Version: DTC 1.5.0-g5c3513f6
pnv_dt_serial has a line which is supposed to set the interrupt-parent of the
"isa-serial@i3f8" node to the phandle of "lpc@0".
To that end, it calls fdt_get_phandle as shown below:
_FDT((fdt_setprop_cell(fdt, node, "interrupt-parent", fdt_get_phandle(fdt,
The function fdt_get_phandle fails to find the property "phandle" (or
"linux,phandle") for the lpc node. Consequently, pnv_dt_serial sets
the interrupt-parent to 0.
Now boot the qemu-system-ppc64 powernv machine, and extract the fdt by
using the qemu monitor's pmemsave command, taking help of the OPAL
firmware's messages to locate the fdt in the physical ram.
qemu-system-ppc64 -m 1g -machine powernv,num-chips=1 \
-cpu power9 -smp 2,cores=2,threads=1 -accel tcg,thread=multi \
-kernel ./vmlinux \
-append 'disable_radix' \
-serial mon:stdio -nographic -nodefaults
The kernel vmlinux contains nothing but a single instruction which
loops infintely, so that we can gather OPAL's messages, especially the
[ 0.168845963,5] INIT: Starting kernel at 0x20000000, fdt at
0x304b0b70 14404 bytes
Once the fdt is dumped to a file, run the following:
'dtc -O dtb -I dts -o out.dts dtb'
After a few warnings, the dtc application crashes because an assertion
out.dts: Warning (unit_address_vs_reg): /lpcm-opb@6030000000000/lpc@0: node
has a unit name, but no reg property
out.dts: Warning (simple_bus_reg): /lpcm-opb@6030000000000/lpc@0: missing or
empty reg/ranges property
out.dts: Warning (avoid_unnecessary_addr_size): /ibm,opal: unnecessary
#address-cells/#size-cells without "ranges" or child "reg" property
out.dts: Warning (unique_unit_address): /interrupt-controller@0: duplicate
unit-address (also used in node /memory@0)
out.dts: Warning (chosen_node_stdout_path): /chosen:linux,stdout-path: Use
dtc: livetree.c:575: get_node_by_phandle: Assertion `generate_fixups' failed.
Aborted (core dumped)
The assertion is fired because get_node_by_phandle receives a phandle
value of 0, which is unexpected, unless fixups are needed (They are
not, when running the dtc command).
Back inside pnv_dt_serial, if the line that sets "interrupt-parent"
for the serial device node is commented out, the dtc crash is
prevented. Looking at hw/ppc/e500.c, it takes care of allocating
necessary phandle values in the nodes, so a similar method can be
adopted for powernv.
The dtb is attached.
Edit: Add version, Correct filenames.
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