rk_gpio: implement PIC masking methods and mask unhandled IRQs

[b1nc0d3x]

Summary

The Rockchip GPIO controller implements PIC operations for the INTRNG framework but is missing four masking methods that INTRNG calls during the filter / ithread handoff:

• pic_disable_intr
• pic_enable_intr
• pic_pre_ithread
• pic_post_ithread

Without them, level-sensitive interrupt sources connected to a Rockchip GPIO pin re-fire continuously while their ithread runs. On a RockPro64 with a FUSB302B Type-C controller (i2c) attached to gpio1 INT_N, the system enters a ~210 kHz interrupt storm the moment the fusb302 driver attaches and INT_N goes low. Observed via:

dtrace -n 'fbt::intr_event_schedule_thread:entry { @[stack()]=count(); }'

Edge-triggered GPIO IRQs were already self-acking and unaffected.

Two complementary changes:

1. Add the four pic_disable_intr / pic_enable_intr / pic_pre_ithread / pic_post_ithread method bodies. Each toggles the pin's RK_GPIO_INTMASK bit so the source is masked during the in-flight ithread window and unmasked on return. This honours the generic INTRNG mask/unmask sequence and mirrors what other arm64 GPIO drivers do (qoriq_gpio, bcm2835_gpio).

2. When the GPIO IRQ filter dispatches a pin and finds no consumer registered, mask the pin at the controller (INTMASK=1, INTEN=0) before continuing. Level-triggered sources keep asserting until acked, so a single stuck pin (e.g. fusb302 INT_N during attach races or after detach) used to flood the console with thousands of "Interrupt pin=N unhandled" lines per second. The mask survives until something re-attaches and re-enables the IRQ via the standard pic_enable_intr path. The single warning line is preserved (now reading "unhandled -- masked") so the underlying issue is still visible.

Test plan

• RockPro64 (rk3399), level-triggered IRQ on gpio1 RK_PA2 (fusb302 INT_N). Before: ~210 kHz storm, top -SH shows swi1:gpio1 pinned. After: 0 spurious IRQs at steady state; pin masks correctly after a detach.
• Same board, edge-triggered IRQ on gpio0 (button input) — still fires once per press, no regression.
• Synthesize an unhandled IRQ by raising a GPIO pin with no FDT consumer wired: console shows one "unhandled -- masked" line, storm does not recur.

Suggested reviewers

manu, mhorne, andrew, mmel — arm64 / Rockchip / INTRNG maintainers per git log. Not @-mentioned to avoid spam if the GitHub handles don't match; happy to ping on request.

Notes

First in a series of patches landing the RockPro64 USB-C DisplayPort + audio path. Successor patches (drm_fb_helper hotplug fix, usbc PD framework, fusb302, rk_typec_phy DP altmode, rk_cdn_dp) will follow in their own PRs after this one gets a sign-of-life from a reviewer.

This patch is independent of the rest of that series and useful on its own for anyone running a Rockchip board with a level-triggered GPIO interrupt source.

Author: Kyle Crenshaw <B1nc0d3x@gmail.com>

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@evadot wants to review changes to sys/arm64/rockchip