Board-level Linux integration, U-Boot, device trees, kernel drivers and peripheral bring-up. Separate power and hardware checks from software adaptation, and define a recoverable boot path.
Use /sys/power/pm_wakeup_irq as a bounded attribution clue, then correlate it with the same suspend attempt’s trace and device evidence. In Linux v6.12 it exposes the current first recorded wake IRQ, not the interrupt armed first, an exhaustive event list, or proof of the physical cause of every wake. Applicability: this article pins Linux v6.12 wakeup.c,…
Validate a voltage/frequency change as an ordered transaction with observable intermediate states. A final frequency readback cannot show whether the supply was prepared first, whether a later step failed, or whether software still describes the previous operating point. Review the exact transition implementation before designing the capture or recovery test. Applicability: this article pins Linux…
A device can be runtime-suspended while its shared power domain remains on. Test the device state and domain state separately, then identify the peer, subdomain, policy, or provider decision that keeps the domain active. Treating every successful device suspension as a domain power-off guarantee produces false failures and unsafe workarounds. Applicability: this article pins Linux…
Separate an RTC alarm match from an asserted interrupt pin and a successful host wake. On the NXP PCF8523, a latched alarm flag can coexist with disabled alarm output or a pin still configured as CLKOUT. A later read showing that time passed the alarm is not evidence that the sleeping host received a usable…
A failed suspend attempt needs two kinds of recovery: the failing callback must undo its own partial changes, and the power-management core must unwind phases that other devices completed successfully. Do not assume that returning an error automatically schedules the matching resume callback for the failed phase. Applicability: this article pins Linux v6.12 system suspend…
Give every latency-sensitive operation an explicit PM QoS owner and remove its request when that operation finishes. The effective CPU latency constraint is aggregated across owners, so closing one application’s request need not relax the system. Diagnose the surviving owner before changing idle-state policy globally. Applicability: this article pins Linux v6.12 with CONFIG_CPU_IDLE and the…
Compare the USB configuration descriptor, the host’s successful remote-wakeup feature request, and the device controller’s actual signaling path before blaming a host that stays asleep. These are separate pieces of evidence. A device can advertise remote wakeup and remember host permission while its selected driver still lacks the software operation needed to initiate it. Applicability:…
A device can return its runtime-PM usage count to zero and still miss every apparent autosuspend opportunity because its last-busy timestamp keeps moving. Trace the timestamp updates and autosuspend requests together. Do not diagnose a reference leak from active status alone, and do not shorten the delay until the source of the updates is understood….
Make resume dependencies explicit in both topology and callback phase. Linux can order a child after its parent and a consumer after a declared supplier, but that does not make a resource initialized in a later phase available to an earlier callback. Diagnose the first invalid dependency edge instead of adding an arbitrary delay. Applicability:…
Diagnose a non-waking device by recording three distinct Linux facts: the driver declares wake capability, policy currently permits system wake, and the IRQ or bus wake mechanism was actually armed for the selected sleep state. A working runtime interrupt or a successful sysfs write proves less than this complete chain. Applicability: this guide pins device…