[PATCH AUTOSEL 6.18] clk: qcom: clk-rpmh: Make all VRMs optional
From: Sasha Levin
Date: Mon Aug 31 2026 - 10:39:00 EST
From: Alexander Koskovich <akoskovich@xxxxx>
[ Upstream commit 25b8f50b0622689cd1f7233e452407ce777a479e ]
Some VRMs aren't present on all boards, so mark them as optional. This
prevents probe failures on boards where not all VRMs are present.
This resolves an issue seen on the Nothing Phone (4a) Pro (Eliza) where
probe fails due to RPMH_RF_CLK5 not being present on the board, this is
due to this device having a slightly different PMIC configuration from
the Eliza MTP.
This matches the downstream approach of marking all VRMs as optional
and makes the previous clka_optional handling redundant.
Signed-off-by: Alexander Koskovich <akoskovich@xxxxx>
Reviewed-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20260414-clk-rpmh-vrm-opt-v3-1-8ca21469ffbc@xxxxx
Signed-off-by: Bjorn Andersson <andersson@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
LLM Generated explanations, may be completely bogus:
# Stable Backport Analysis: `clk: qcom: clk-rpmh: Make all VRMs
optional`
**Local tree:** Linux **6.18.43** (`v6.18.43-1-gc7f0dac02d232`)
---
## PHASE 1: COMMIT MESSAGE FORENSICS
### Step 1.1: Subject line
**Record:** `[clk: qcom: clk-rpmh]` `[Make]` — Make all VRM (Voltage
Resource Manager) RPMh clocks optional when absent from cmd-db,
preventing platform-device probe failure.
### Step 1.2: Tags
**Record:**
| Tag | Value |
|-----|-------|
| Signed-off-by | Alexander Koskovich \<akoskovich@xxxxx\> (author) |
| Reviewed-by | Konrad Dybcio \<konrad.dybcio@xxxxxxxxxxxxxxxx\> |
| Reviewed-by | Dmitry Baryshkov \<dmitry.baryshkov@xxxxxxxxxxxxxxxx\> |
| Link | https://lore.kernel.org/r/20260414-clk-rpmh-vrm-
opt-v3-1-8ca21469ffbc@xxxxx |
| Signed-off-by | Bjorn Andersson \<andersson@xxxxxxxxxx\> (maintainer)
|
Notable: **Two Qualcomm subsystem reviewers** reviewed. No `Fixes:`,
`Cc: stable`, `Reported-by:`, or syzbot tags (expected for manual
review). Lore link present but blocked by bot protection during fetch.
### Step 1.3: Body analysis
**Record:**
- **Bug:** Some VRM RPMh clock resources are absent from cmd-db on
certain board/PMIC variants; driver probe fails with `-ENODEV`.
- **Symptom:** `clk-rpmh` platform driver probe fails; clock provider
never registers → boot failure or severely broken clock tree on
affected boards.
- **Concrete case:** Nothing Phone (4a) Pro (Eliza / SM7750) —
`RPMH_RF_CLK5` not present due to different PMIC vs. MTP reference
board.
- **Root cause:** Previous `clka_optional` flag only skipped missing
resources whose names start with `"clka"`, missing `rfclka*`,
`lnbclka*`, and other VRM resource names.
- **Fix approach:** Treat all VRM clocks (`res_addr ==
CLK_RPMH_VRM_EN_OFFSET`) as optional when cmd-db has no address;
remove per-platform `clka_optional` flag.
### Step 1.4: Hidden bug fix?
**Record:** **Yes.** Despite the subject not using "fix", this is a
probe/boot failure bug fix disguised as making resources optional. The
existing `clka_optional` mechanism in this tree is incomplete.
---
## PHASE 2: DIFF ANALYSIS
### Step 2.1: Inventory
**Record:**
| File | Changes |
|------|---------|
| `drivers/clk/qcom/clk-rpmh.c` | ~20 lines net (remove struct field, 3
`.clka_optional = true` lines, rewrite probe condition) |
**Functions modified:** `clk_rpmh_probe()` (probe path only)
**Scope:** Single-file, surgical fix.
### Step 2.2: Code flow change
**Record:**
**Hunk 1 — `struct clk_rpmh_desc`:**
- Before: Per-platform `bool clka_optional` flag.
- After: Field removed entirely.
**Hunk 2 — Platform descriptors (`sm8550`, `sm8650`, `sm8750`):**
- Before: `.clka_optional = true`.
- After: Flag removed (logic now universal for all VRM clocks).
**Hunk 3 — `clk_rpmh_probe()` error path:**
- Before: On missing cmd-db address, skip only if `desc->clka_optional
&& res_name starts with "clka"`.
- After: On missing cmd-db address, skip if `rpmh_clk->res_addr ==
CLK_RPMH_VRM_EN_OFFSET` (value 4, set at compile time by
`DEFINE_CLK_RPMH_VRM`).
**Critical detail verified:** The check uses the statically initialized
`rpmh_clk->res_addr` (offset 4 for VRM, 0 for ARC) **before** line 968
adds the cmd-db base address. ARC/BCM clocks still fail probe if
missing.
### Step 2.3: Bug mechanism
**Record:**
- **Category:** Logic/correctness fix — incomplete optional-resource
handling on error path.
- **Mechanism:** VRM clocks defined via `DEFINE_CLK_RPMH_VRM` use
resource names like `"rfclka5"`, `"lnbclka2"`, `"clka6"`. The old
check only matched names starting with `"clka"` (4 chars), so
`"rfclka5"` (starts with `"rfcl"`) was **not** treated as optional
even on platforms with `clka_optional = true`.
- **Example in this tree:** `glymur` has `RF_CLK5` using `"rfclka5"`
with **no** `clka_optional` flag. `sm8750` has `clka_optional = true`
but uses `"rfclka1"`/`"rfclka2"`/`"rfclka3"` for RF clocks — also not
covered.
### Step 2.4: Fix quality
**Record:**
- **Obviously correct:** Uses the existing `CLK_RPMH_VRM_EN_OFFSET`
discriminator already baked into clock definitions; matches downstream
Qualcomm approach per commit message.
- **Minimal:** No API changes, no new features.
- **Regression risk:** Low-medium. Platforms like `sc7280` that
previously failed probe on any missing VRM will now skip silently.
Qualcomm reviewers accepted this trade-off; ARC/essential clocks still
required.
---
## PHASE 3: GIT HISTORY INVESTIGATION
### Step 3.1: Blame
**Record:** Shallow tree (50 commits total); `git blame` on probe lines
attributes everything to `a112b91dd6349` (unrelated sunrpc commit —
artifact of shallow history). Cannot determine original introduction
commit of `clka_optional` from this checkout. **The buggy code is
present in 6.18.43** (verified by reading the file).
### Step 3.2: Fixes: tag
**Record:** Not applicable — no `Fixes:` tag in commit message.
### Step 3.3: File history
**Record:** `git log --oneline -- drivers/clk/qcom/clk-rpmh.c` returns
only one entry due to shallow history. Cannot trace related series.
Patch is **standalone** (single file, no "patch X/Y" markers).
### Step 3.4: Author context
**Record:** Alexander Koskovich is actively upstreaming Eliza/SM7750
(Nothing Phone 4a Pro) support. Same author filed SM7750 SoC ID patches.
Strong Qualcomm/mobile focus.
### Step 3.5: Dependencies
**Record:** **No dependencies.** Fix is self-contained in `clk-rpmh.c`.
Verified with `git apply --check` — **applies cleanly** to this tree.
Does not require Eliza DTS or `kaanapali`/`eliza-rpmh-clk` compatibles
(those are absent from this tree).
---
## PHASE 4: MAILING LIST AND EXTERNAL RESEARCH
### Step 4.1: Original discussion
**Record:** Lore URL and patch.msgid.link blocked by Anubis bot
protection. `b4 dig` with wrong commit hash returned unrelated sunrpc
thread. Subject indicates **v3** of patch series. Could not read
reviewer stable nominations directly.
### Step 4.2: Reviewers
**Record:** Konrad Dybcio and Dmitry Baryshkov (Qualcomm clock/ARM
maintainers) — strong subsystem review signal, verified from commit
message tags.
### Step 4.3: Bug report
**Record:** Nothing Phone (4a) Pro (Eliza / SM7750) reported in commit
message. Web search confirms SM7750 = Eliza codename, used in Nothing
Phone (4a) Pro. **Eliza DTS / `qcom,eliza-rpmh-clk` is NOT in this
6.18.43 tree** (no `eliza.dtsi`, no eliza compatibles in `clk-rpmh.c`).
### Step 4.4: Related patches
**Record:** Eliza base DT series uses `compatible = "qcom,eliza-rpmh-
clk"` (mainline, not in this tree). Glymur is a **different** SoC
(Snapdragon X2 Elite). The reported device is Eliza, not Glymur.
### Step 4.5: Stable list
**Record:** Could not search stable@ list (lore blocked). No evidence
found of prior stable rejection.
---
## PHASE 5: CODE SEMANTIC ANALYSIS
### Step 5.1: Key functions
**Record:** `clk_rpmh_probe()`, `of_clk_rpmh_hw_get()` (unchanged).
### Step 5.2: Callers
**Record:** `clk_rpmh_probe` registered as `platform_driver` `.probe`
for `clk-rpmh`. Invoked during kernel boot device enumeration for every
Qualcomm SoC with an RPMh clock controller node in DT. **High impact** —
affects all `qcom,*-rpmh-clk` platforms.
### Step 5.3: Callees
**Record:** `cmd_db_read_addr()`, `cmd_db_read_aux_data()`,
`devm_clk_hw_register()`, `devm_of_clk_add_hw_provider()`.
### Step 5.4: Reachability
**Record:** Triggered at boot on any board where cmd-db lacks a VRM
resource entry that the platform clock table references. User-visible:
device won't boot or clocks won't register. **Reachable on every
affected Qualcomm board at boot.**
### Step 5.5: Similar patterns
**Record:** `sm8650` clock table already has a comment documenting a
missing `clka3` resource on some platforms — evidence that optional VRM
handling is expected behavior. The name-prefix approach was always
incomplete.
---
## PHASE 6: CROSS-REFERENCE WITH LOCAL TREE (6.18.43)
### Step 6.1: Buggy code exists?
**Record:** **YES.** `clka_optional` field and name-prefix check present
at lines 70, 683, 715, 884, 946–947. `CLK_RPMH_VRM_EN_OFFSET` defined at
line 20. Platforms in match table include `glymur`, `sm8750`, `sm8650`,
`sm8550`, `sc7280`, and others.
**Concrete buggy examples in this tree:**
- `glymur`: `RF_CLK5` → `"rfclka5"`, no `clka_optional` → probe fails if
missing.
- `sm8750`: `clka_optional = true` but RF clocks use
`"rfclka1"`/`"rfclka2"`/`"rfclka3"` → **not** covered by `"clka"`
prefix check.
- `sm8750.dtsi` exists with `compatible = "qcom,sm8750-rpmh-clk"` — in-
tree platform affected.
**Not in this tree:** Eliza/SM7750 (`qcom,eliza-rpmh-clk`), Nothing
Phone 4a Pro DT, `kaanapali` platform from newer mainline.
### Step 6.2: Backport complications
**Record:** **Clean apply** — verified with `git apply --check`. No
conflicts expected.
### Step 6.3: Related fixes already present?
**Record:** `git log --grep` found no existing "VRM optional" fix.
`clka_optional` mechanism is present but incomplete — this commit
completes it.
---
## PHASE 7: SUBSYSTEM CONTEXT
### Step 7.1: Subsystem criticality
**Record:** `drivers/clk/qcom/` — **IMPORTANT** (clock subsystem for
Qualcomm ARM64 SoCs). Not universal like core mm/net, but boot-critical
for affected hardware.
### Step 7.2: Activity
**Record:** Active development — `sm8750`, `glymur`, `sm8650` platforms
present. Recent SoC bring-up area.
---
## PHASE 8: IMPACT AND RISK
### Step 8.1: Who is affected
**Record:** Users of Qualcomm SoCs using RPMh VRM clocks — specifically
board variants with PMIC/cmd-db configurations that omit some VRM
resources. In this tree: **sm8750** (has DTS), **glymur** (driver only,
no arch DTS), and potentially **sc7280**/**sdx65**/**sdx75** if variant
boards omit RF clocks.
### Step 8.2: Trigger conditions
**Record:** Boot on a board whose cmd-db firmware lacks an entry for a
VRM clock listed in the platform's RPMh clock table. **Common** for
commercial phone variants vs. reference MTP boards. Not userspace-
triggerable; boot-time only.
### Step 8.3: Failure mode severity
**Record:** `clk-rpmh` probe returns `-ENODEV` → RPMh clock provider
missing → **boot failure or severely broken system**. Severity:
**CRITICAL** when triggered.
### Step 8.4: Risk-benefit
**Record:**
- **Benefit:** HIGH for affected Qualcomm boards (boot fix); fixes known
incomplete `clka_optional` for `sm8750`/`sm8650`/`sm8550`; aligns with
downstream.
- **Risk:** LOW — small diff, Qualcomm-reviewed, uses existing type
discriminator. Slight risk of masking cmd-db misconfiguration on older
platforms (e.g., `sc7280`), but this is the intended Qualcomm
behavior.
- **Ratio:** Benefit outweighs risk.
---
## PHASE 9: FINAL SYNTHESIS
### Step 9.1: Evidence summary
**FOR backport:**
- Fixes real boot-time probe failure on Qualcomm board variants
- Incomplete `clka_optional` logic is a genuine bug already in 6.18.43
(`sm8750` RF clocks use `"rfclka*"` names not covered)
- `glymur` platform in driver has same bug pattern (`RF_CLK5` /
`"rfclka5"`)
- Small (~20 line), single-file, applies cleanly
- Reviewed by two Qualcomm maintainers
- Hardware quirk / probe failure — standard stable material
- `sm8750.dtsi` with RPMh clock controller is in this tree
**AGAINST backport:**
- Specific reported device (Nothing Phone 4a Pro / Eliza / SM7750) not
yet in 6.18.43 tree
- Broadens optional behavior for older platforms (`sc7280`, etc.)
without documented user reports in this tree
- No syzbot/fuzzer signal; single vendor-reported case for hardware not
yet upstream in this stable series
**Unresolved:** Could not read lore review thread; cannot confirm
explicit stable nomination from reviewers.
### Step 9.2: Stable rules checklist
| Criterion | Result |
|-----------|--------|
| 1. Obviously correct and tested? | **PASS** — logic is clear; Qualcomm
reviewers approved; matches downstream |
| 2. Fixes real bug affecting users? | **PASS** — probe failure on board
variants; `sm8750` latent bug verified in code |
| 3. Important issue? | **PASS** — boot failure (CRITICAL when
triggered) |
| 4. Small and contained? | **PASS** — ~20 lines, one file |
| 5. No new features/APIs? | **PASS** — removes flag, fixes existing
behavior |
| 6. Can apply to local tree? | **PASS** — clean apply verified |
### Step 9.3: Exception category
**Record:** **Hardware quirk / workaround** — VRM resources legitimately
absent on some board/PMIC variants; driver must not fail probe.
### Step 9.4: Decision rationale
This tree (6.18.43) already contains the incomplete `clka_optional`
mechanism and multiple Qualcomm platforms (`sm8750` with DTS, `glymur`
in driver) where VRM clocks use `"rfclka*"` resource names that the
current name-prefix check does not cover. The fix is small, self-
contained, Qualcomm-reviewed, and prevents boot-time probe failures — a
critical failure mode. While the specifically reported Nothing Phone 4a
Pro (Eliza/SM7750) platform is not yet in this tree, the underlying bug
exists in code and platform tables that **are** present, and the patch
applies cleanly without dependencies.
---
## Verification
- **[Phase 1]** `git describe HEAD` → v6.18.43; parsed all commit
message tags
- **[Phase 2]** Read `drivers/clk/qcom/clk-rpmh.c` lines 19–20, 66–71,
116–122, 347–387, 660–901, 917–976; confirmed VRM vs ARC `res_addr`
initialization and probe check timing
- **[Phase 2]** Verified `"rfclka5"` does not match `strncmp(...,
"clka", 4)` (compares `"rfcl"` vs `"clka"`)
- **[Phase 3]** `git blame` on probe lines; `git log` on file (shallow —
limited history)
- **[Phase 3]** `git apply --check` with adapted patch → **exit 0**
(clean apply)
- **[Phase 4]** WebFetch lore URL → blocked by Anubis; web search
confirmed SM7750 = Eliza = Nothing Phone 4a Pro SoC
- **[Phase 4]** `b4 dig -c a112b91dd6349` → unrelated sunrpc thread
(wrong hash)
- **[Phase 5]** `grep clk_rpmh_probe` → platform_driver probe at boot
- **[Phase 6]** `grep clka_optional` → 4 occurrences in tree; `grep
eliza/kaanapali/sm7750` in clk driver → none
- **[Phase 6]** `glob *eliza*` → 0 files; `grep glymur` in `arch/` → no
DTS; `grep rpmh-clk` in `arch/arm64/boot/dts/qcom` → sm8750.dtsi
present
- **[Phase 6]** Read `sm8750.dtsi:3618-3625` — `qcom,sm8750-rpmh-clk`
present
- **[Phase 6]** Read `glymur_rpmh_clocks` — includes `RF_CLK5` with
`rf_clk5_a` / `"rfclka5"`
- **[Phase 7]** Read `Documentation/process/stable-kernel-rules.rst` —
hardware quirk explicitly listed as stable-worthy
- **UNVERIFIED:** Original lore review thread content and any explicit
stable nomination
- **UNVERIFIED:** Whether any 6.18.43-supported board (sm8750-mtp/qrd)
currently hits missing VRM resources in practice
- **UNVERIFIED:** When `clka_optional` was originally introduced
(shallow git history)
**YES**## Result
**Backport recommendation: YES** for Linux **6.18.43**.
The commit fixes a real boot-time bug in `drivers/clk/qcom/clk-rpmh.c`:
the existing `clka_optional` logic only skips missing resources whose
names start with `"clka"`, so VRM clocks named `"rfclka*"`,
`"lnbclka*"`, etc. can still make probe fail with `-ENODEV`. That
affects platforms already in this tree (notably `sm8750`, and `glymur`
in the driver).
The patch is small (~20 lines), applies cleanly, was reviewed by
Qualcomm maintainers, and fits the hardware-quirk/boot-failure category
for stable. The Nothing Phone 4a Pro (Eliza/SM7750) case from the commit
message isn’t in this tree yet, but the underlying bug in the RPMh clock
driver is.
drivers/clk/qcom/clk-rpmh.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/drivers/clk/qcom/clk-rpmh.c b/drivers/clk/qcom/clk-rpmh.c
index 63c38cb47bc45..82f18e15cd77b 100644
--- a/drivers/clk/qcom/clk-rpmh.c
+++ b/drivers/clk/qcom/clk-rpmh.c
@@ -66,8 +66,6 @@ struct clk_rpmh {
struct clk_rpmh_desc {
struct clk_hw **clks;
size_t num_clks;
- /* RPMh clock clkaN are optional for this platform */
- bool clka_optional;
};
static DEFINE_MUTEX(rpmh_clk_lock);
@@ -680,7 +678,6 @@ static struct clk_hw *sm8550_rpmh_clocks[] = {
static const struct clk_rpmh_desc clk_rpmh_sm8550 = {
.clks = sm8550_rpmh_clocks,
.num_clks = ARRAY_SIZE(sm8550_rpmh_clocks),
- .clka_optional = true,
};
static struct clk_hw *sm8650_rpmh_clocks[] = {
@@ -712,7 +709,6 @@ static struct clk_hw *sm8650_rpmh_clocks[] = {
static const struct clk_rpmh_desc clk_rpmh_sm8650 = {
.clks = sm8650_rpmh_clocks,
.num_clks = ARRAY_SIZE(sm8650_rpmh_clocks),
- .clka_optional = true,
};
static struct clk_hw *sc7280_rpmh_clocks[] = {
@@ -881,7 +877,6 @@ static struct clk_hw *sm8750_rpmh_clocks[] = {
static const struct clk_rpmh_desc clk_rpmh_sm8750 = {
.clks = sm8750_rpmh_clocks,
.num_clks = ARRAY_SIZE(sm8750_rpmh_clocks),
- .clka_optional = true,
};
static struct clk_hw *glymur_rpmh_clocks[] = {
@@ -943,8 +938,7 @@ static int clk_rpmh_probe(struct platform_device *pdev)
if (!res_addr) {
hw_clks[i] = NULL;
- if (desc->clka_optional &&
- !strncmp(rpmh_clk->res_name, "clka", sizeof("clka") - 1))
+ if (rpmh_clk->res_addr == CLK_RPMH_VRM_EN_OFFSET)
continue;
dev_err(&pdev->dev, "missing RPMh resource address for %s\n",
--
2.53.0