arm(64)/dts/connect4: Reduce SPI frequency of KSZ9897 #30
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iluminat23
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Aug 4, 2021
| @@ -199,7 +199,7 @@ | |||
| ksz9897: ksz9897@0 { | |||
| compatible = "microchip,ksz9897"; | |||
| reg = <0>; | |||
| spi-max-frequency = <50000000>; | |||
| spi-max-frequency = <25000000>; | |||
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It turned out that if the SPI frequency for accessing the KSZ9897 is too high (more than 33MHz) the data read from the PHY registers may be corrupted if at the same time the USB is accessed. This may be caused by interferences between the SPI and USB signals. However reducing the frequency to a value below or equal to 33MHz for the SPI communication with the switch eliminates this effect. To be on the save side choose a value of 25MHz. Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
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[ Upstream commit d412137 ] The perf_buffer fails on system with offline cpus: # test_progs -t perf_buffer test_perf_buffer:PASS:nr_cpus 0 nsec test_perf_buffer:PASS:nr_on_cpus 0 nsec test_perf_buffer:PASS:skel_load 0 nsec test_perf_buffer:PASS:attach_kprobe 0 nsec test_perf_buffer:PASS:perf_buf__new 0 nsec test_perf_buffer:PASS:epoll_fd 0 nsec skipping offline CPU #24 skipping offline CPU #25 skipping offline CPU #26 skipping offline CPU #27 skipping offline CPU #28 skipping offline CPU #29 skipping offline CPU #30 skipping offline CPU #31 test_perf_buffer:PASS:perf_buffer__poll 0 nsec test_perf_buffer:PASS:seen_cpu_cnt 0 nsec test_perf_buffer:FAIL:buf_cnt got 24, expected 32 Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED Changing the test to check online cpus instead of possible. Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20211021114132.8196-2-jolsa@kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org>
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It turned out that if the SPI frequency for accessing the KSZ9897 is too
high (more than 33MHz) the data read from the PHY registers may be
corrupted if at the same time the USB is accessed. This may be caused by
interferences between the SPI and USB signals.
However reducing the frequency to a value below or equal to 33MHz for the
SPI communication with the switch eliminates this effect.
To be on the save side choose a value of 25MHz.
Signed-off-by: Lino Sanfilippo l.sanfilippo@kunbus.com