From: Haikun Zhou <[email protected]> [ Upstream commit 844e71ba7d7a50c5ffa29d147afaeaafb19b39e4 ]
MB116AS01'3 raw edid: 00 ff ff ff ff ff ff 00 21 63 03 12 00 00 00 00 00 23 01 04 95 1a 0e 78 23 e7 05 9c 5b 56 93 27 21 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 36 1c 56 92 50 00 1c 30 60 18 a8 00 00 90 10 00 00 18 00 00 00 fd 00 28 3c 30 30 07 01 0a 20 20 20 20 20 20 00 00 00 fe 00 48 4b 43 20 4d 59 20 20 20 20 0a 20 20 00 00 00 fe 00 4d 42 31 31 36 41 53 30 31 27 33 20 20 01 cb 70 20 79 02 00 22 00 14 1c 1a 01 84 55 05 91 00 5f 00 17 00 ff 02 1b 00 09 00 07 00 2b 00 06 27 00 28 3b 00 00 81 00 13 72 1a 00 00 03 01 28 3c 00 00 00 00 00 00 3c 00 00 00 00 25 01 09 1c 1a 01 1c 1a 01 28 3c 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 e7 90 Signed-off-by: Haikun Zhou <[email protected]> Reviewed-by: Douglas Anderson <[email protected]> Signed-off-by: Douglas Anderson <[email protected]> Link: https://patch.msgid.link/20260701013018.2621972-1-zhouhaik...@huaqin.corp-partner.google.com Signed-off-by: Sasha Levin <[email protected]> --- LLM Generated explanations, may be completely bogus: Local tree is **6.18.y** (`v6.18.53`, `VERSION=6 PATCHLEVEL=18`). The MB116AS01'3 table entry is **not** in `v6.18.53`. The driver, HKC table, `delay_200_500_e80`, and unknown-panel `WARN_ON` path are present. This is a one-line panel ID / quirk for an existing driver. =============================================================== PHASE 1: COMMIT MESSAGE FORENSICS =============================================================== Step 1.1: PARSE THE SUBJECT LINE Record: `[drm/panel-edp] [Support] [add MB116AS01'3 eDP panel table entry]` - Subsystem: `drm/panel-edp` - Verb: "Support" — hardware enablement / ID addition, not a refactor Step 1.2: PARSE ALL COMMIT MESSAGE TAGS Record: - `Signed-off-by: Haikun Zhou <[email protected] partner.google.com>` (author; Huaqin/Google partner) - `Reviewed-by: Douglas Anderson <[email protected]>` (panel-edp reviewer in MAINTAINERS) - `Signed-off-by: Douglas Anderson <[email protected]>` (maintainer applied it) - `Link: https://patch.msgid.link/20260701013018.2621972-1- [email protected]` - No `Fixes:`, `Reported-by:`, `Tested-by:`, `Cc: stable` (absence expected for this review) - Ignored: `Signed-off-by: Sasha Levin` and `[Upstream commit ...]` (pipeline markers) Step 1.3: ANALYZE THE COMMIT BODY TEXT Record: - Bug description: the panel is missing from `edp_panels[]`. The body is the raw EDID (base block + extension), not a crash log. - Symptom: unmatched generic `edp-panel` uses conservative delays and hits `WARN_ON(!detected_panel)` at probe. - Version info: none in the message. Author date is 2026-07-01; `v6.18` is 2025-11-30, so this landed after this series branched. - Root cause: HKC ID `0x1203` was not in the delay/quirk table. Step 1.4: DETECT HIDDEN BUG FIXES Record: Not a disguised cleanup. It is an explicit panel ID / power- sequencing quirk. That is the same class as PCI/USB ID additions. =============================================================== PHASE 2: DIFF ANALYSIS - LINE BY LINE =============================================================== Step 2.1: INVENTORY THE CHANGES Record: - File: `drivers/gpu/drm/panel/panel-edp.c` (`+1 / -0`) - Function/table: `edp_panels[]` - Scope: single-file, one-line surgical addition Step 2.2: UNDERSTAND THE CODE FLOW CHANGE Record: - Before: HKC `0x1203` is not in `edp_panels[]`. `find_edp_panel()` returns NULL. - After: match `EDP_PANEL_ENTRY('H', 'K', 'C', 0x1203, &delay_200_500_e80, "MB116AS01'3")`. - Path: `panel_edp_probe()` → compatible `"edp-panel"` → `generic_edp_panel_probe()` → EDID panel ID lookup. - After match: `desc->delay = *detected_panel->delay` (`hpd_absent=200`, `unprepare=500`, `enable=80`). - Unmatched: `WARN_ON` plus `panel_edp_set_conservative_timings()` (`unprepare=2000`, `enable=200`). Step 2.3: IDENTIFY THE BUG MECHANISM Record: **Hardware workaround / device ID** (category h). - Mechanism: EDID mfg `HKC` (bytes `21 63`) and product `0x1203` (bytes `03 12`) were not mapped to delays. The panel name in EDID descriptor 0xFE is `MB116AS01'3` (`0x27` = `'`). - Fix: add the existing `delay_200_500_e80` preset (already used by many 11.6" BOE/CMN entries). Step 2.4: ASSESS THE FIX QUALITY Record: - Obviously correct: one table row, sorted under existing HKC entries (`0x1203` before `0x2d51`). - Minimal; no unrelated edits. - Regression risk: very low. Lookup is ID-specific; other panels unchanged. - `delay_200_500_e80` already exists in this tree (verified at `panel- edp.c:1760` on `v6.18.53`). =============================================================== PHASE 3: GIT HISTORY INVESTIGATION =============================================================== Step 3.1: BLAME THE CHANGED LINES Record: - Table introduced with `panel-edp` split: `5f04e7ce392db` ("Split eDP panels out of panel-simple"). - HKC rows already in `v6.18` / `v6.18.53` (`0x2d51`, `0x2d5b` MB116AN01, `0x2d5c` MB116AN01-2). - `delay_200_500_e80` from `4d53cf8147950` ("Add several generic edp panels"), present in this tree. - This ID is new; the table and delay helper are old. Step 3.2: FOLLOW THE FIXES: TAG Record: No `Fixes:` tag. N/A. The gap is a missing table row, not a later regression. Step 3.3: CHECK FILE HISTORY FOR RELATED CHANGES Record: - `v6.18..v6.18.53` already contains many similar one-line panel adds (AUO, BOE, CSW, LG, Sharp, mt8189 Chromebook panels). - Standalone; not `patch X/Y`. Step 3.4: CHECK THE AUTHOR'S OTHER COMMITS Record: - Haikun Zhou has other `panel-edp` ID/delay commits (`CSW MNB601LS1-4`, `CMN N116BCJ-EAK`). - Reviewer Douglas Anderson is `R:` for "DRM DRIVER FOR GENERIC EDP PANELS" in MAINTAINERS. Step 3.5: CHECK FOR DEPENDENT/PREREQUISITE COMMITS Record: None. Needs only `EDP_PANEL_ENTRY`, HKC table, and `delay_200_500_e80`, all in `v6.18.53`. Dry-run against the `v6.18.53` blob: hunk applied (offset -5). Standalone apply: yes. =============================================================== PHASE 4: MAILING LIST AND EXTERNAL RESEARCH =============================================================== Step 4.1: FIND THE ORIGINAL PATCH DISCUSSION Record: - `b4 dig -c 9e55b14301666`: V2 at https://patch.msgid.link/202607010130 [email protected] - `b4 dig -a`: - v1 2026-06-29: `MB116AS01-3` (hyphen), msgid `20260629012200.248066-1-...` - v2 2026-07-01: `MB116AS01'3` (apostrophe, matches EDID) - Applied version is v2. - Doug Anderson: Reviewed-by and pushed to drm-misc-next as `844e71ba7d7a`. - No NAK found. - UNVERIFIED: exact v1 review text (lore 403, MARC 404). Name change v1→v2 is verified from the two patches. Step 4.2: CHECK WHO REVIEWED THE PATCH Record (`b4 dig -w`): - To/Cc: `[email protected]`, `[email protected]`, `[email protected]`, `[email protected]`, `linux- [email protected]`, `[email protected]`, `[email protected]` - Subsystem reviewer included and signed off. Step 4.3: SEARCH FOR THE BUG REPORT Record: No syzbot/bugzilla. Evidence is the EDID dump in the patch. Author is a hardware partner, typical for ChromeOS panel IDs. Step 4.4: CHECK FOR RELATED PATCHES AND SERIES Record: Standalone 1/1. drm-misc pull for 7.3-rc1 lists it under **panel-edp: quirks** with MB116AS01 (https://lists.openwall.net/linux- kernel/2026/08/20/246). Step 4.5: CHECK STABLE MAILING LIST HISTORY Record: lore.kernel.org/stable search returned 403. UNVERIFIED: no stable-list thread found. Official `v6.18.53` already took the same class of panel-edp ID patches, so there is no local policy against this type. =============================================================== PHASE 5: CODE SEMANTIC ANALYSIS =============================================================== Step 5.1: IDENTIFY KEY FUNCTIONS IN THE DIFF Record: No function body change. Data: `edp_panels[]`. Consumers: `find_edp_panel()`, `generic_edp_panel_probe()`. Step 5.2: TRACE CALLERS Record: - `find_edp_panel()` ← `generic_edp_panel_probe()` - `generic_edp_panel_probe()` ← `panel_edp_probe()` when OF compatible is `"edp-panel"` - `panel_edp_probe()` ← `panel_edp_platform_probe()` / `panel_edp_dp_aux_ep_probe()` - Context: device probe / display bring-up, not IRQ-hot. Step 5.3: TRACE CALLEES Record: Table is data only. Probe reads EDID, matches ID, copies `panel_delay`. Delays used in `panel_edp_prepare_once()` (`hpd_absent`) and `panel_edp_enable()` (`enable`). Step 5.4: FOLLOW THE CALL CHAIN Record: Userspace does not call this directly. Plug in the panel (Chromebook/laptop DT `edp-panel` on DP AUX) and it runs at probe/resume. Reachable on machines with this HKC panel. Step 5.5: SEARCH FOR SIMILAR PATTERNS Record: Same file is a long ID table. HKC already has three entries. Many sibling "Add … panel" commits are already in official 6.18.y. =============================================================== PHASE 6: CROSS-REFERENCING AGAINST THE LOCAL TREE =============================================================== Step 6.1: DOES THE BUGGY CODE EXIST IN THIS TREE? Record: Yes. `v6.18.53` has `edp_panels[]`, HKC rows, `find_edp_panel()`, and: ``` if (WARN_ON(!panel->detected_panel)) { ... "Unknown panel ... using conservative timings" ``` `MB116AS01` / `0x1203` is **not** in `v6.18` or `v6.18.53`. Bug = missing quirk for hardware that this driver already enumerates. Step 6.2: CHECK FOR BACKPORT COMPLICATIONS Record: Clean apply to `v6.18.53` (dry-run succeeded, offset -5). Surrounding HKC context matches. Difficulty: clean apply. Step 6.3: CHECK IF RELATED FIXES ARE ALREADY HERE Record: No other MB116AS01'3 / HKC `0x1203` fix in this series. Nearby HKC MB116AN01 entries do not cover `0x1203`. =============================================================== PHASE 7: SUBSYSTEM AND MAINTAINER CONTEXT =============================================================== Step 7.1: IDENTIFY THE SUBSYSTEM AND ITS CRITICALITY Record: `drivers/gpu/drm/panel/` — DRM panel. Criticality: **IMPORTANT** for devices with this panel (blank/slow display, boot `WARN_ON`); **PERIPHERAL** for everyone else (ID match is a no-op). Step 7.2: ASSESS SUBSYSTEM ACTIVITY Record: Mature table, still getting ID/quirk adds. Official 6.18.y already backports them. Not a new subsystem. =============================================================== PHASE 8: IMPACT AND RISK ASSESSMENT =============================================================== Step 8.1: DETERMINE WHO IS AFFECTED Record: Driver-specific / hardware-specific: machines whose eDP EDID is HKC `0x1203` (MB116AS01'3), typically ChromeOS/partner laptops. No effect on other panels. Step 8.2: DETERMINE THE TRIGGER CONDITIONS Record: Every probe of `"edp-panel"` with that EDID (boot and often resume). Not a race. Unprivileged users do not trigger it except by using the device. Step 8.3: DETERMINE THE FAILURE MODE SEVERITY Record: - Without the entry: `WARN_ON` stack on probe (noisy, can trip panic-on- warn) **plus** conservative delays (2s unprepare vs 500ms; 200ms enable vs 80ms). Conservative path is designed so the panel still usually works. - Failure mode: boot warning + slower power sequencing, not a universal oops. - Severity: **MEDIUM** for affected hardware (warning + wrong timings); **LOW** globally. - Still qualifies under the device-ID / quirk exception. Step 8.4: CALCULATE RISK-BENEFIT RATIO Record: - Benefit: high for that panel (correct T3/T12-style delays, no `WARN_ON`); zero for others. - Risk: very low (1 line, existing delay struct, ID-gated). - Ratio: strongly favors backport. =============================================================== PHASE 9: FINAL SYNTHESIS =============================================================== Step 9.1: COMPILE THE EVIDENCE FOR: - One-line ID/quirk in an existing driver (`panel-edp.c` / `edp_panels[]`). - Matches stable exceptions: **device ID** and **hardware quirk** (drm- misc pull even labeled it "panel-edp: quirks"). - Avoids `WARN_ON` and 2s conservative unprepare on this panel. - `delay_200_500_e80`, HKC table, and lookup path exist in this 6.18 tree. - Reviewed and applied by the panel-edp maintainer. - Official 6.18.y already contains many identical panel-edp ID backports. - Applies cleanly to `v6.18.53`. AGAINST: - Not a UAF/crash/corruption fix for all users; unmatched panels usually still work with conservative delays. - No `Reported-by` from end users; vendor EDID add. UNRESOLVED: - Exact v1 review comments (lore/MARC fetch failed). - Whether this was discussed on stable@ (lore/stable 403). Step 9.2: APPLY THE STABLE RULES CHECKLIST 1. Obviously correct and tested? **PASS** — one sorted table row; maintainer Reviewed-by and merged. 2. Fixes a real bug that affects users? **PASS** — missing quirk: `WARN_ON` + wrong power delays on this panel. 3. Important issue? **PASS** under the device-ID/quirk exception (boot warning + incorrect sequencing on real hardware). Not a core panic. 4. Small and contained? **PASS** — +1 line, one file. 5. No new features or APIs? **PASS** — no new driver, syscall, or userspace API; only a table ID. 6. Can apply to the local tree? **PASS** — dry-run against `v6.18.53` succeeded. Step 9.3: CHECK FOR EXCEPTION CATEGORIES Record: **Device ID addition to existing driver** and **hardware quirk/workaround**. Automatic YES class. Step 9.4: MAKE YOUR DECISION This tree is 6.18.y. The driver already identifies unknown eDP panels and warns. Adding HKC `0x1203` is the same kind of ID/quirk 6.18.y already takes. Benefit is real for that hardware; risk is negligible. What it solves for stable users: Chromebook/laptop panels with EDID HKC `0x1203` get the intended 200/500/80 ms sequencing and stop hitting the unknown-panel `WARN_ON`. Risk vs benefit: one ID-gated line vs boot warning and multi-second conservative delays. Favor backport. Verification: - [Phase 1] Tags: Haikun Zhou SOB, Douglas Anderson Reviewed-by + SOB, lore msgid link; no Fixes/Reported-by/Cc:stable - [Phase 1] Body is raw EDID; decoded mfg HKC (`0x2163`) product `0x1203`; name `MB116AS01'3` - [Phase 2] Diff: +1 `EDP_PANEL_ENTRY` in `edp_panels[]`; delay `&delay_200_500_e80` - [Phase 2] Unmatched path: `WARN_ON` + `unprepare=2000`/`enable=200` in `generic_edp_panel_probe()` (verified in this tree and `v6.18.53`) - [Phase 3] `git describe HEAD` → `v6.18.53-5049-g0f0bdc2b0dffb`; `make kernelversion` → 6.18.53 - [Phase 3] `git merge-base --is-ancestor 9e55b14301666 v6.18.53` → NO (not in official 6.18.53) - [Phase 3] `git grep MB116AS01 v6.18.53 -- panel-edp.c` → not present; HKC `0x2d51/0x2d5b/0x2d5c` present - [Phase 3] `delay_200_500_e80` present at line 1760 on `v6.18.53` - [Phase 3] `v6.18..v6.18.53` already has multiple `drm/panel-edp: Add … panel` commits - [Phase 4] `b4 dig -c`: V2 lore URL; `b4 dig -a`: v1 hyphen name, v2 apostrophe; `b4 dig -w`: dianders, dri-devel, drm maintainers - [Phase 4] LKML: Doug Reviewed-by, pushed `844e71ba7d7a` to drm-misc- next - [Phase 4] drm 7.3-rc1 pull lists MB116AS01 under panel-edp quirks - [Phase 4] UNVERIFIED: v1 review text; stable@ discussion (HTTP 403/404) - [Phase 5] Call chain: `panel_edp_probe` → `generic_edp_panel_probe` → `find_edp_panel`; delays used in prepare/enable - [Phase 6] Dry-run `patch --dry-run` of this commit onto `v6.18.53` `panel-edp.c`: succeeded (offset -5) - [Phase 7] MAINTAINERS: Douglas Anderson is `R:` for panel-edp.c - [Phase 8] Severity: WARN_ON + wrong delays on this panel; ID-gated so other hardware unaffected **YES** drivers/gpu/drm/panel/panel-edp.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c index f2ae333a32d8c..0da04d75e4e96 100644 --- a/drivers/gpu/drm/panel/panel-edp.c +++ b/drivers/gpu/drm/panel/panel-edp.c @@ -2061,6 +2061,7 @@ static const struct edp_panel_entry edp_panels[] = { EDP_PANEL_ENTRY('E', 'T', 'C', 0x0000, &delay_50_500_e200_d200_po2e335, "LP079QX1-SP0V"), + EDP_PANEL_ENTRY('H', 'K', 'C', 0x1203, &delay_200_500_e80, "MB116AS01'3"), EDP_PANEL_ENTRY('H', 'K', 'C', 0x2d51, &delay_200_500_e200, "Unknown"), EDP_PANEL_ENTRY('H', 'K', 'C', 0x2d5b, &delay_200_500_e200, "MB116AN01"), EDP_PANEL_ENTRY('H', 'K', 'C', 0x2d5c, &delay_200_500_e200, "MB116AN01-2"), -- 2.53.0
