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TLP Headers traced by HiSilicon PCIe tune and trace device (PTT) in
4DW format are shown in the document as below:
bits [31:30] [ 29:25 ][24][23][22][21][ 20:11 ][ 10:0 ]
|-----|---------|---|---|---|---|-------------|-------------|
DW0 [ Fmt ][ Type ][T9][T8][TH][SO][ Length ][ Time ]
DW1 [ Header DW1 ]
DW2 [ Header DW2 ]
DW3 [ Header DW3 ]
Problem:
The DW0 bit field layout of the hisi_ptt_4dw union does not match the
actual bit ordering in little-endian memory, causing incorrect field
decoding.
Test on Kunpeng 930 SOC, generating data flow with `iperf` commands:
- server side:
iperf -s
- client side:
iperf -c $ip_addr -t 30
Trace the TLP headers with hisi_ptt on server side at the same time:
perf record -e hisi_ptt12_0/type=4,filter=0x05101,direction=2,format=0/ \
--max-size 50M -o perf.data &
The trace aims to capture completion TLPs, learn more in the document:
https://docs.kernel.org/trace/hisi-ptt.html
Decode perf.data with hisi_ptt decoder:
perf report -D
The hisi_ptt decoder produces the following result:
[...perf headers and other information]
. ... HISI PTT data: size 8388608 bytes
. 00000000: 68 87 20 94 Format 3 Type 1a T9 0 T8 1 TH 1 SO 1 Length 10 Time 4a1
. 00000004: 40 00 00 00 Header DW1
. 00000008: 40 00 01 51 Header DW2
. 0000000c: 00 00 00 00 Header DW3
[...other hisi_ptt TLP headers]
According to PCIe r5.0 sec 2.2.1, the Fmt & Type of Cpl/CplD is supposed
to be 8b'00001010' / 8b'01001010'
However, the Format & Type decoder analyzing result is 8b'01111010'.
It does not match field encodings of any TLP.
Correct decoder result should be:
[...perf headers and other information]
. ... HISI PTT data: size 8388608 bytes
. 00000000: 94 20 87 68 Format 2 Type a T9 0 T8 0 TH 0 SO 1 Length 10 Time 768
. 00000004: 00 00 00 40 Header DW1
. 00000008: 51 01 00 40 Header DW2
. 0000000c: 00 00 00 00 Header DW3
[...other hisi_ptt TLP headers]
To solve the problem:
1. Drop the union and C bitfield struct, store the raw DW value in
a plain uint32_t, and extract the fields with FIELD_GET() against
GENMASK/BIT masks declared in the header so they can be reused by
other translation units. The masks are portable across endianness and
compilers.
2. Print all DW hex values in big-endian byte order for readability,
matching the bit field layout shown in the 4DW format diagram.
3. Read the DW value with get_unaligned_le32() instead of an unaligned
pointer cast, avoiding both strict-aliasing violations and
alignment hazards on hosts that do not support unaligned access.
Cc: stable@vger.kernel.org
Fixes:
|
||
|---|---|---|
| .. | ||
| coresight | ||
| postprocess | ||
| rv | ||
| boottime-trace.rst | ||
| debugging.rst | ||
| eprobetrace.rst | ||
| events-kmem.rst | ||
| events-msr.rst | ||
| events-nmi.rst | ||
| events-pci-controller.rst | ||
| events-pci.rst | ||
| events-power.rst | ||
| events.rst | ||
| fprobe.rst | ||
| fprobetrace.rst | ||
| ftrace-design.rst | ||
| ftrace-uses.rst | ||
| ftrace.rst | ||
| function-graph-fold.vim | ||
| hisi-ptt.rst | ||
| histogram-design.rst | ||
| histogram.rst | ||
| hwlat_detector.rst | ||
| index.rst | ||
| intel_th.rst | ||
| kprobes.rst | ||
| kprobetrace.rst | ||
| mmiotrace.rst | ||
| osnoise-tracer.rst | ||
| remotes.rst | ||
| ring-buffer-design.rst | ||
| ring-buffer-map.rst | ||
| stm.rst | ||
| sys-t.rst | ||
| timerlat-tracer.rst | ||
| tracepoint-analysis.rst | ||
| tracepoints.rst | ||
| uprobetracer.rst | ||
| user_events.rst | ||