Add debug knobs to pcie_brcmstb#6745
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pelwell merged 1 commit intoraspberrypi:rpi-6.12.yfrom Mar 28, 2025
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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 <jonathan@raspberrypi.com>
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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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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.