[PATCH AUTOSEL 6.18-5.10] ata: libata-pmp: add JMicron JMS562 quirk
From: Sasha Levin
Date: Mon Aug 31 2026 - 13:12:33 EST
From: Xu Rao <raoxu@xxxxxxxxxxxxx>
[ Upstream commit c62aff1174cf88e10716c7513702443c47551fc6 ]
JMicron JMS562, as used in QNAP QDA-A2AR RAID1 adapters, may
keep the exported ATA device not ready while the array is rebuilding.
In this state, libata may repeatedly try to softreset and classify
the fan-out link. On the affected adapter, this can time out, make
PMP/SCR access fail, and eventually disable the fan-out link before
the RAID volume is exported.
A failing boot shows the fan-out link failing SRST, PMP access
timing out, SCR read failing, and the link being disabled:
ata4.00: softreset failed (device not ready)
ata4.15: qc timeout after 3000 msecs (cmd 0xe4)
ata4.00: failed to read SCR 0 (Emask=0x4)
ata4.00: failed to recover link after 3 tries, disabling
After that, the root filesystem on the exported RAID volume cannot
be found.
Add JMS562 to the existing JMicron PMP quirk that disables LPM,
avoids softreset on fan-out links, and assumes an ATA device. This
prevents libata from dropping the exported RAID volume during rebuild
recovery.
Signed-off-by: Xu Rao <raoxu@xxxxxxxxxxxxx>
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
Signed-off-by: Niklas Cassel <cassel@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
LLM Generated explanations, may be completely bogus:
## Phase 1: Commit Message Forensics
**Step 1.1 — Subject line**
- Record: `[ata: libata-pmp] [add] JMicron JMS562 quirk for QNAP
QDA-A2AR RAID adapter boot failure during array rebuild`
**Step 1.2 — Tags**
- Record:
- `Signed-off-by: Xu Rao <raoxu@xxxxxxxxxxxxx>` (author)
- `Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>` (libata
maintainer)
- `Signed-off-by: Niklas Cassel <cassel@xxxxxxxxxx>` (committer)
- No `Fixes:`, `Reported-by:`, `Tested-by:`, `Cc:
stable@xxxxxxxxxxxxxxx`, or `Link:` tags
- Notable: maintainer review from Damien Le Moal; no syzbot/fuzzer
involvement
**Step 1.3 — Body analysis**
- Record:
- **Bug:** JMicron JMS562 PMP (QNAP QDA-A2AR RAID1 adapter) keeps
exported ATA device "not ready" during RAID rebuild
- **Symptom:** libata repeatedly softresets/classifies fan-out link →
PMP/SCR timeouts → link disabled → root filesystem on RAID volume
not found at boot
- **Failure log:** `softreset failed (device not ready)`, `qc
timeout`, `failed to read SCR 0`, `failed to recover link after 3
tries, disabling`
- **Root cause:** Missing quirk; libata error-handling path
incompatible with JMS562 behavior during rebuild
- **Fix approach:** Add device ID `0x0562` to existing JMicron quirk
block (disable LPM, avoid SRST, assume ATA)
- **Version info:** None stated in commit message
**Step 1.4 — Hidden bug fix detection**
- Record: Not hidden — this is an explicit hardware quirk fix. "Add
quirk" language is standard for ATA PMP workarounds; the commit
clearly describes a real boot failure.
---
## Phase 2: Diff Analysis
**Step 2.1 — Inventory**
- Record:
- Files: `drivers/ata/libata-pmp.c` (+6, -1)
- Function: `sata_pmp_quirks()`
- Scope: Single-file, surgical quirk addition (~7 lines net)
**Step 2.2 — Code flow change**
- Record:
- **Before:** JMicron vendor `0x197b` quirk applied only to device IDs
`0x2352` (JMB350) and `0x0325` (JMB394)
- **After:** Same quirk also applied to `0x0562` (JMS562)
- **Affected path:** PMP attach → `sata_pmp_quirks()` → per-link flags
set at initialization, before normal I/O
- **Flags set:** `ATA_LFLAG_NO_LPM | ATA_LFLAG_NO_SRST |
ATA_LFLAG_ASSUME_ATA` on all fan-out links
**Step 2.3 — Bug mechanism**
- Record:
- **Category:** Hardware workaround / logic correctness fix
- **Mechanism:** Without quirk, libata performs softreset (SRST) and
link classification on a device that legitimately reports "not
ready" during RAID rebuild. SRST/classify timeouts trigger error
recovery that disables the link before the RAID volume becomes
available. Quirk prevents SRST and assumes ATA class, matching
proven JMicron PMP behavior.
**Step 2.4 — Fix quality**
- Record:
- Obviously correct: extends an existing, proven quirk pattern for the
same vendor
- Minimal scope: one device ID + comment
- Low regression risk: only affects JMS562 PMP hardware; flags mirror
those already used for sibling JMicron chips
- No API, structure, or behavioral changes beyond this device
---
## Phase 3: Git History Investigation
**Step 3.1 — Blame**
- Record:
- JMicron quirk block introduced by `0afc6f5ba9541` (2011, Thermaltake
BlackX Duet / JMB350)
- JMB394 added by `efb9e0f4f4378` (2014) — that commit included `Cc:
stable@xxxxxxxxxxxxxxx`
- Current tree has the quirk for `0x2352` and `0x0325` but not
`0x0562`
- Bug is not from a recent regression — it's a missing quirk for
hardware that was never covered
**Step 3.2 — Fixes: tag**
- Record: No `Fixes:` tag present; not applicable.
**Step 3.3 — Related file history**
- Record:
- Recent `libata-pmp.c` changes in this tree are unrelated (FBS/CBS
defer, tracepoints, spelling)
- Commit `c62aff1174cf8` is the only mainline change to this quirk
block since v6.18
- Standalone: v2 submission notes "sent as [PATCH 6/6], but this is a
standalone patch"
**Step 3.4 — Author context**
- Record: Xu Rao (UnionTech) — first ATA contribution in this tree.
Patch reviewed and committed by libata maintainers (Damien Le Moal,
Niklas Cassel).
**Step 3.5 — Dependencies**
- Record: No dependencies. `git apply --check` against current tree
succeeds. Quirk infrastructure and target `else if` block both exist
in v6.18.44.
---
## Phase 4: Mailing List and External Research
**Step 4.1 — Original discussion**
- Record:
- Lore URL: https://patch.msgid.link/71B4D0BBEC4F886F+20260610052835.1
111181-1-raoxu@xxxxxxxxxxxxx
- Series: v1 as `[PATCH 6/6]`, v2 as standalone `[PATCH v2]`
(committed version)
- Damien Le Moal: "It is really unfortunate that JMicron keeps having
these issues. But I do not see any way around this" → `Reviewed-by:`
- No NAKs found
- No explicit stable nomination in thread
**Step 4.2 — Reviewers**
- Record: CC'd to `dlemoal@xxxxxxxxxx`, `cassel@xxxxxxxxxx`, `linux-
ide@xxxxxxxxxxxxxxx`. Reviewed by libata maintainer Damien Le Moal.
**Step 4.3 — Bug report**
- Record: Real-world hardware bug on QNAP QDA-A2AR; concrete dmesg log
in commit message. No external bug tracker link. Severity for affected
users: cannot boot when root is on rebuilding RAID volume.
**Step 4.4 — Related patches**
- Record: Originally part of a 6-patch series but maintainer confirmed
v2 is standalone with no code changes from v1. No other series patches
required.
**Step 4.5 — Stable list history**
- Record: No stable-list discussion found for this specific fix.
Precedent: JMB394 quirk (`efb9e0f4f4378`) was explicitly nominated for
stable.
---
## Phase 5: Code Semantic Analysis
**Step 5.1 — Key functions**
- Record: `sata_pmp_quirks()` (modified), called from
`sata_pmp_attach()`
**Step 5.2 — Callers**
- Record:
- `sata_pmp_attach()` defined in `libata-pmp.c`, called from `libata-
eh.c` during error-handling/recovery when attaching a PMP device
- Triggered during SATA PMP enumeration at boot or hot-plug
**Step 5.3 — Callees**
- Record: Uses `sata_pmp_gscr_vendor()`, `sata_pmp_gscr_devid()`,
`ata_for_each_link()` — all standard libata PMP helpers
**Step 5.4 — Reachability**
- Record: Triggered whenever a JMicron JMS562 PMP is detected. Affects
boot path for systems using QNAP QDA-A2AR as root storage. Not
userspace-triggerable directly, but affects every boot on affected
hardware.
**Step 5.5 — Similar patterns**
- Record: Identical quirk pattern already used for JMB350 (`0x2352`) and
JMB394 (`0x0325`) in the same function. Same vendor, same flags, same
failure mode (SRST breaks detection).
---
## Phase 6: Cross-Reference Against Local Tree
**Step 6.1 — Buggy code present?**
- Record:
- Local tree: **v6.18.44** (`git describe HEAD`)
- Commit `c62aff1174cf8` is **NOT** in this tree (`git merge-base
--is-ancestor` → NOT)
- Buggy code **exists**: lines 460–472 of `drivers/ata/libata-pmp.c`
have JMicron quirk without `0x0562`
- JMicron quirk infrastructure present since v3.x era; bug is absence
of device ID, not post-branch regression
**Step 6.2 — Backport complications**
- Record: Clean apply confirmed (`git apply --check` passes). No
conflicting changes to this hunk in v6.18.y. Expected difficulty:
**clean apply**.
**Step 6.3 — Related fixes already present?**
- Record: No existing fix for JMS562 in this tree. `git log
--grep="JMS562"` returns nothing.
---
## Phase 7: Subsystem and Maintainer Context
**Step 7.1 — Subsystem**
- Record: `drivers/ata/` — libata PMP (Port Multiplier). Criticality:
**IMPORTANT** (storage/boot path for affected hardware).
**Step 7.2 — Activity**
- Record: Mature subsystem with occasional quirk additions. PMP quirk
table is stable; changes are typically small device-ID additions.
---
## Phase 8: Impact and Risk Assessment
**Step 8.1 — Who is affected**
- Record: Users of QNAP QDA-A2AR RAID1 adapters (JMicron JMS562 PMP)
booting from or accessing RAID volumes during rebuild. Driver-
specific, but impact is total for those users (unbootable system).
**Step 8.2 — Trigger conditions**
- Record: Boot or PMP attach while JMS562-managed RAID array is
rebuilding. Reproducible on affected hardware per commit message. Not
timing-dependent race — deterministic behavior mismatch.
**Step 8.3 — Failure severity**
- Record: Link disabled → storage unavailable → root filesystem not
found. **Severity: CRITICAL** for affected users (unbootable system,
potential data access loss during recovery window).
**Step 8.4 — Risk-benefit**
- Record:
- **Benefit: HIGH** — restores bootability on real hardware with
documented failure mode
- **Risk: VERY LOW** — 7-line quirk addition, scoped to one PCI device
ID, mirrors existing proven quirk
- **Ratio: Strongly favors backport**
---
## Phase 9: Final Synthesis
**Step 9.1 — Evidence summary**
FOR backport:
- Real hardware bug with concrete dmesg and boot failure
- Hardware quirk/workaround — explicit stable exception category
- Small, surgical, obviously correct
- Reviewed by libata maintainer
- Applies cleanly to v6.18.44
- Standalone, no dependencies
- Precedent: prior JMicron PMP quirks backported to stable
AGAINST backport:
- Affects narrow hardware population (QNAP QDA-A2AR users)
- No syzbot/security angle
- No explicit stable nomination
UNRESOLVED: None material to the decision.
**Step 9.2 — Stable rules checklist**
1. Obviously correct and tested? **PASS** — extends existing quirk;
reviewed by maintainer
2. Fixes real bug affecting users? **PASS** — boot failure on QNAP
QDA-A2AR
3. Important issue? **PASS** — unbootable system / root FS unavailable
(CRITICAL for affected users)
4. Small and contained? **PASS** — 7 lines, one file
5. No new features or APIs? **PASS** — device quirk only
6. Can apply to local tree? **PASS** — clean apply verified;
prerequisite code present
**Step 9.3 — Exception category**
- Record: **Hardware quirk/workaround** — adding device ID `0x0562` to
existing JMicron PMP quirk table
**Step 9.4 — Decision rationale**
This commit adds the JMicron JMS562 (`0x0562`) to an existing, well-
tested PMP quirk block in `sata_pmp_quirks()`. Without it, libata's
softreset and link-recovery logic on the QNAP QDA-A2AR adapter can
disable the fan-out link during RAID rebuild, preventing the root
filesystem from appearing at boot. The fix is minimal, matches the
pattern used for other JMicron chips since 2011, applies cleanly to the
v6.18.44 tree, and was reviewed by the libata maintainer. This is
textbook stable material: a hardware-specific workaround for a serious,
reproducible boot failure.
---
## Verification
- [Phase 1] Parsed commit `c62aff1174cf8`: subject, body, tags
(Reviewed-by: Damien Le Moal; no Fixes/Reported-by/stable tags)
- [Phase 2] Diff: +6/-1 in `sata_pmp_quirks()`, adds `devid == 0x0562`
to JMicron quirk
- [Phase 3] `git blame -L 460,472`: quirk block from 2011/2014 commits;
JMS562 not present
- [Phase 3] `git show efb9e0f4f4378`: JMB394 quirk had `Cc:
stable@xxxxxxxxxxxxxxx`
- [Phase 3] `git merge-base --is-ancestor c62aff1174cf8 HEAD`: commit
NOT in tree
- [Phase 3] `git apply --check` on commit diff: applies cleanly
- [Phase 4] `b4 dig -c c62aff1174cf8`: found lore thread
- [Phase 4] `b4 dig -a`: v1 as patch 6/6, v2 standalone (committed
version)
- [Phase 4] `b4 dig -w`: CC'd dlemoal, cassel, linux-ide
- [Phase 4] mbox: Damien Le Moal Reviewed-by, no NAKs, v2 confirmed
standalone
- [Phase 5] `grep sata_pmp_attach`: caller in `libata-eh.c:3379`
- [Phase 5] Read `include/linux/libata.h`: confirmed flag meanings for
NO_SRST, ASSUME_ATA, NO_LPM
- [Phase 6] `git describe HEAD`: v6.18.44
- [Phase 6] Read `drivers/ata/libata-pmp.c:460-472`: buggy code (missing
0x0562) confirmed present
- [Phase 6] `git log v6.18..master -- drivers/ata/libata-pmp.c`: only
this commit touches quirk block
- [Phase 8] Commit message dmesg: softreset failure → link disabled →
root FS not found
**YES**
drivers/ata/libata-pmp.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c
index 48ac09d9031e6..299b1823e0d09 100644
--- a/drivers/ata/libata-pmp.c
+++ b/drivers/ata/libata-pmp.c
@@ -457,8 +457,13 @@ static void sata_pmp_quirks(struct ata_port *ap)
* otherwise. Don't try hard to recover it.
*/
ap->pmp_link[ap->nr_pmp_links - 1].flags |= ATA_LFLAG_NO_RETRY;
- } else if (vendor == 0x197b && (devid == 0x2352 || devid == 0x0325)) {
+ } else if (vendor == 0x197b &&
+ (devid == 0x0562 || devid == 0x2352 || devid == 0x0325)) {
/*
+ * 0x0562: JMicron JMS562, as used in QNAP QDA-A2AR RAID1
+ * adapters. The exported device may stay not ready
+ * while the array is rebuilding, and SRST/classify can
+ * time out before the RAID volume is exported.
* 0x2352: found in Thermaltake BlackX Duet, jmicron JMB350?
* 0x0325: jmicron JMB394.
*/
--
2.53.0