Add debug knobs to pcie_brcmstb #6745
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pelwell
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Mar 27, 2025
P33M
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Mar 27, 2025
Add two features that assist in diagnosing link instability issues. The debugfs additions allow for snapshots of the Physical Layer statistics registers to be taken, during either free-running capture or after a hardware-controlled capture interval. To arm the capture engine (and reset the stats counters), write an integer N to: /sys/kernel/debug/pcie@<addr>/stats_trigger The engine will run forever with a value of 0, or disarm after N microseconds. To snapshot the hardware stats counters, write to: /sys/kernel/debug/pcie@<addr>/stats_snapshot Reading this file will return the snapshot. If no writes have occurred since boot, the snapshot will be of the initial link training period. The ltssm_trace module parameter printk's the states during initial link startup, in situations where failure to establish the link is a fatal error. Signed-off-by: Jonathan Bell <[email protected]>
pelwell
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Mar 28, 2025
popcornmix
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Mar 31, 2025
kernel: overlay: Rework/fix the Pi 5 MIDI UART overlays See: raspberrypi/linux#6743 kernel: Add debug knobs to pcie_brcmstb See: raspberrypi/linux#6745 kernel: ARM64: dts: Add sd and sd_poll_once params to CM5 See: raspberrypi/linux#6744 firmware: Vl805 reset improvements
popcornmix
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kernel: overlay: Rework/fix the Pi 5 MIDI UART overlays See: raspberrypi/linux#6743 kernel: Add debug knobs to pcie_brcmstb See: raspberrypi/linux#6745 kernel: ARM64: dts: Add sd and sd_poll_once params to CM5 See: raspberrypi/linux#6744 firmware: Vl805 reset improvements
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Flaky NVMe HATs/drives will frequently bounce the link, degrading performance. Or completely fall over, if the link is so bad that a completion timeout occurs. Capturing error counts (with manual triggers for intermittent failures) sheds light on this.
Bad layout and routing on a CM4/5 interface board isn't going to be diagnosable from a link trace, but you can at least tell if your remote terminations are being sensed and/or the remote EP is trying to talk to you.