From: Quan Zhou quan.zhou@mediatek.com
[ Upstream commit 066f417be5fd8c7fe581c5550206364735dad7a3 ]
Set the MT76_STATE_MCU_RUNNING bit only after mt7921_load_clc() has successfully completed. Previously, the MCU_RUNNING state was set before loading CLC, which could cause conflict between chip mcu_init retry and mac_reset flow, result in chip init fail and chip abnormal status. By moving the state set after CLC load, firmware initialization becomes robust and resolves init fail issue.
Signed-off-by: Quan Zhou quan.zhou@mediatek.com Reviewed-by: druth@chromium.org Link: https://patch.msgid.link/19ec8e4465142e774f17801025accd0ae2214092.1763465933... Signed-off-by: Felix Fietkau nbd@nbd.name Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
# Commit Analysis: wifi: mt76: mt792x: fix wifi init fail by setting MCU_RUNNING after CLC load
## 1. COMMIT MESSAGE ANALYSIS
**Subject:** Clearly indicates a bug fix ("fix wifi init fail")
**Problem described:** Setting `MT76_STATE_MCU_RUNNING` bit before CLC (Country/Legal Configuration) load completion could cause conflicts between MCU init retry and mac_reset flows, resulting in chip initialization failure and abnormal chip status.
**Tags present:** - `Signed-off-by:` Quan Zhou (MediaTek - chip vendor) and Felix Fietkau (mt76 maintainer) - `Reviewed-by:` druth@chromium.org (Chrome OS kernel team - indicates real-world Chromebook impact) - No explicit `Cc: stable@vger.kernel.org` tag - No explicit `Fixes:` tag
## 2. CODE CHANGE ANALYSIS
The change is extremely simple and surgical:
**Before the fix:** ```c set_bit(MT76_STATE_MCU_RUNNING, &dev->mphy.state); // State set here err = mt7921_load_clc(dev, mt792x_ram_name(dev)); // CLC load after ```
**After the fix:** ```c err = mt7921_load_clc(dev, mt792x_ram_name(dev)); // CLC load first set_bit(MT76_STATE_MCU_RUNNING, &dev->mphy.state); // State set after success ```
**Technical mechanism:** - `MT76_STATE_MCU_RUNNING` indicates the MCU is fully operational - Setting this flag prematurely (before CLC load) could allow other code paths to think the MCU is ready when it's not - If something triggers MCU init retry or mac_reset during CLC load, there's a race condition - The conflict causes complete initialization failure and abnormal chip state
**Why fix is correct:** - The state bit should only be set when initialization is truly complete - This ensures no code sees MCU_RUNNING during the vulnerable CLC loading phase - Error handling remains intact (if CLC load fails, function returns error)
## 3. CLASSIFICATION
- **Type:** Bug fix - initialization failure fix - **NOT** a feature addition - Fixes a real runtime bug affecting device usability
## 4. SCOPE AND RISK ASSESSMENT
| Factor | Assessment | |--------|------------| | Lines changed | ~6 lines (just moving 1 line in 2 files) | | Files touched | 2 (mt7921/mcu.c, mt7925/mcu.c) | | Complexity | Very low - simple reordering | | Regression risk | LOW - no logic changes, just timing | | Subsystem | Wireless driver (contained) |
The change is almost purely a reordering operation within the same function. If CLC load succeeds, the state gets set (same as before, just later). If it fails, function returns error anyway.
## 5. USER IMPACT
**Affected hardware:** MediaTek mt7921 and mt7925 WiFi chips
These are **extremely common** chips found in: - Many Chromebooks (Chrome OS review indicates this) - Consumer laptops (Dell, Lenovo, HP, etc.) - USB WiFi adapters - Various PC builds
**Severity:** HIGH - WiFi initialization failure = device doesn't work at all - "chip abnormal status" suggests chip may be left in broken state - Users cannot use their WiFi until reboot or driver reload
## 6. STABILITY INDICATORS
- Reviewed by Chromium kernel team (indicates real-world testing on Chromebooks) - From MediaTek engineer (hardware vendor knows their chip) - Accepted by mt76 maintainer Felix Fietkau - Clean, minimal change with clear rationale
## 7. DEPENDENCY CHECK
The change is self-contained. It only reorders existing function calls within `mt7921_run_firmware()` and `mt7925_run_firmware()`. No new dependencies are introduced.
The mt7921 driver has been in stable kernels for some time. The mt7925 is newer and may not exist in older stable trees, but the mt7921 portion would still be valuable.
## STABLE KERNEL CRITERIA CHECK
| Criterion | Met? | Notes | |-----------|------|-------| | Obviously correct | ✅ | Simple reordering, logic is clear | | Fixes real bug | ✅ | WiFi init failure - real user impact | | Small and contained | ✅ | 6 lines, 2 files, same subsystem | | No new features | ✅ | No new APIs or functionality | | No architectural changes | ✅ | Minimal change |
## RISK vs BENEFIT
**Benefit:** High - Fixes WiFi initialization failure on widely-deployed hardware. Without this fix, affected users may have non-functional WiFi.
**Risk:** Very low - The change is a trivial reordering of two operations. The logic remains identical; only the timing of when the state bit is set changes. The fix has been reviewed by the chip vendor and Chrome OS team.
## CONCLUSION
This commit is an ideal candidate for stable backporting:
1. **Fixes a real, user-visible bug** - WiFi doesn't work 2. **Minimal change** - Just reordering one line in each of two files 3. **Well-reviewed** - MediaTek and Chrome OS review 4. **Low regression risk** - No logic changes, simple timing fix 5. **High user impact** - mt7921/mt7925 are very common chips 6. **Contained scope** - Only affects initialization path of specific driver
The lack of `Cc: stable` tag doesn't disqualify it - many legitimate fixes don't include this tag. The important factors are all positive: it fixes a real bug, is small, safe, and affects real users.
**YES**
drivers/net/wireless/mediatek/mt76/mt7921/mcu.c | 2 +- drivers/net/wireless/mediatek/mt76/mt7925/mcu.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7921/mcu.c index 86bd33b916a9d..edc1df3c071e5 100644 --- a/drivers/net/wireless/mediatek/mt76/mt7921/mcu.c +++ b/drivers/net/wireless/mediatek/mt76/mt7921/mcu.c @@ -646,10 +646,10 @@ int mt7921_run_firmware(struct mt792x_dev *dev) if (err) return err;
- set_bit(MT76_STATE_MCU_RUNNING, &dev->mphy.state); err = mt7921_load_clc(dev, mt792x_ram_name(dev)); if (err) return err; + set_bit(MT76_STATE_MCU_RUNNING, &dev->mphy.state);
return mt7921_mcu_fw_log_2_host(dev, 1); } diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c index 8eda407e4135e..c12b71b71cfc7 100644 --- a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c +++ b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c @@ -1003,10 +1003,10 @@ int mt7925_run_firmware(struct mt792x_dev *dev) if (err) return err;
- set_bit(MT76_STATE_MCU_RUNNING, &dev->mphy.state); err = mt7925_load_clc(dev, mt792x_ram_name(dev)); if (err) return err; + set_bit(MT76_STATE_MCU_RUNNING, &dev->mphy.state);
return mt7925_mcu_fw_log_2_host(dev, 1); }