BFE Engineering
42fb386f60
Replace every em dash with real punctuation (rewrites, not hyphen swaps) in docs, code comments, scripts, configs, and the port records; convert en dashes, curly quotes, ellipsis glyphs, arrows, and section signs to ASCII; drop machine-writing tell phrases from living docs. ADR titles now use a colon. The M2 bring-up DTS model string carried an em dash into the patch series and its record echoes; fixed at both, and the full series re-verified to apply cleanly onto pristine 6.18.46. One comment in freshness.h deliberately names the em dash glyph the UI renders as the unknown mark; that is data, kept as prose naming it. Verified: cargo tests (sim, config-lint, rs485-bridge), shellcheck, both driver MC/DC harnesses, patches-apply.
58 lines
2.4 KiB
Markdown
58 lines
2.4 KiB
Markdown
# GT911 capacitive touch: VERIFIED on warden-c8a3 (2026-08-25)
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Touch works on our self-built 6.18.46 (`_b`): the WardenOS UI responds to
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taps/swipes (confirmed by hand on the physical panel). Objective evidence:
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```
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Goodix-TS 3-0014: ID 911, version: 1060
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input: Goodix Capacitive TouchScreen as .../i2c-3/3-0014/input/input0
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```
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`/dev/input/event0` is created and held open by `warden-ui` (pid 517, exclusive
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EVIOCGRAB: which is why a second reader sees 0 bytes; the events go to the UI).
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## Root cause on `_b`
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Touch was dead on `_b` while fine on `_a`. dmesg showed:
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```
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module goodix: .gnu.linkonce.this_module section size must match the kernel's
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built struct module size at run time
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```
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The **stock rootfs ships `goodix.ko` built for the 5.10 kernel**; it cannot load
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on our 6.18 (`struct module` layout mismatch). Our 6.18 `.config` did **not** have
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the driver at all (`# CONFIG_TOUCHSCREEN_GOODIX is not set`), and the DTS had no
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GT911 node, so nothing drove the GT911.
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## Fix
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1. **`CONFIG_TOUCHSCREEN_GOODIX=y`**: build the mainline Goodix driver *into* the
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kernel (no module -> no vermagic/struct mismatch; the stale rootfs `.ko` still
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fails to insmod but is now harmless).
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2. **GT911 DT node** under `&i2c3` (matches the vendor 86-panel wiring):
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```
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touchscreen@14 {
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compatible = "goodix,gt911";
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reg = <0x14>;
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interrupt-parent = <&gpio0>;
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interrupts = <RK_PA0 IRQ_TYPE_EDGE_FALLING>;
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irq-gpios = <&gpio0 RK_PA0 GPIO_ACTIVE_HIGH>;
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reset-gpios = <&gpio3 RK_PD0 GPIO_ACTIVE_HIGH>;
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};
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```
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plus `pinctrl-0 = <&i2c3m2_xfer &tp_rst &tp_irq>` on `&i2c3` and the `tp_rst`
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(GPIO3_D0) / `tp_irq` (GPIO0_A0) pin groups.
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Polarity note: mainline goodix drives reset **logical 0 = hold, 1 = release**, and
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the GT911 reset is physically active-low, so `reset-gpios` is **ACTIVE_HIGH**
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(logical==physical), NOT the ACTIVE_LOW the vendor 5.10 driver used. Confirmed
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against mainline gt911 DT examples (sun7i-a20-wexler-tab7200 etc.): both irq-gpios
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and reset-gpios are ACTIVE_HIGH; reg 0x14 needs irq-gpios for address select.
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Non-fatal: `Direct firmware load for goodix_911_cfg.bin failed (-2)`; the GT911
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uses its flashed internal config; touch works without a cfg.bin.
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## Files changed (research/linux-6.18.46)
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- `.config`: `CONFIG_TOUCHSCREEN_GOODIX=y`.
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- `arch/arm/boot/dts/rockchip/rv1106-warden.dts`: GT911 node on `&i2c3`,
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`tp_rst`/`tp_irq` pin groups under `&pinctrl`.
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