[BUG] mt7921e driver loads abnormal firmware "____010000" on ThinkPad T14 Gen 2a, causing Wi-Fi stalls

[yizhe <18093582010@163.com>]

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Hello mt76 maintainers and linux-wireless community,

I am reporting a bug where the `mt7921e` driver consistently loads an abnormal firmware version on my MediaTek MT7921 Wi-Fi adapter, leading to frequent upload/download speed drops to zero.

### 1. Problem Description
- **Hardware**: ThinkPad T14 Gen 2a with MediaTek MT7921 (PCI ID: 14c3:7961).
- **Software**: Arch Linux with kernel `6.12.65-1-lts` (also reproducible on `linux-zen`).
- **Symptom**: Wi-Fi connects but frequently stalls (speed drops to 0 B/s). The driver logs show it is using firmware version `____010000` with a future build time `20250625153703`. Normal external firmware files are ignored.

### 2. Diagnostic Evidence
- The abnormal firmware version appears in dmesg immediately after driver load.
- `modinfo mt7921e` shows the driver is configured for MT7922/MT7961 firmware only, with no entry for MT7921.
- We have confirmed that the correct MT7961 firmware files exist in `/lib/firmware/mediatek/` and are properly compressed.
- Attempts to specify firmware via module parameters (`fw_name`, `wmfw_name`) failed because these parameters are not supported by the current driver.
- **Crucially, a full-system search confirms that the string `____010000` does NOT exist in any kernel module file**, ruling out simple built-in firmware. This suggests a driver logic bug in version reporting or fallback.

### 3. Steps to Reproduce
1. Boot Arch Linux on a ThinkPad T14 Gen 2a with MT7921.
2. Check `sudo dmesg | grep -i "WM Firmware Version"`.
3. Observe the abnormal version `____010000`.

### 4. What has been tried (and failed)
- Placing various MT7961 firmware files with different names and creating symlinks.
- Adding `disable_aspm=1` and attempting firmware path parameters via `modprobe.d`.
- Switching between `linux-zen`, `linux`, and `linux-lts` kernels.
- Completely reinstalling `linux-firmware` and `linux-firmware-mediatek` packages.

### 5. Request
Could you please investigate:
1. Why does the driver report and possibly use this abnormal firmware version?
2. Is the driver's firmware configuration for PCI ID 14c3:7961 incomplete or incorrect?
3. What is the correct way to make the driver load the proper firmware for this device?

The full diagnostic logs are attached below for your reference.

Thank you for your time and work on the mt76 driver.

Full unprocessed dmesg logs are attached as a text file.

Best regards,
[yizhe]

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[-- Attachment #2: mt7921_full_dmesg.log --]
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[    0.126644] Spectre V2 : Enabling Restricted Speculation for firmware calls
[    1.161159] xhci-pci-renesas 0000:06:00.0: failed to load firmware renesas_usb_fw.mem, fallback to ROM
[    3.410422] [drm] Loading DMUB firmware via PSP: version=0x0101002B
[    3.410952] [drm] Found VCN firmware Version ENC: 1.24 DEC: 8 VEP: 0 Revision: 9
[    5.522859] systemd[1]: Clear Stale Hibernate Storage Info was skipped because of an unmet condition check (ConditionPathExists=/sys/firmware/efi/efivars/HibernateLocation-8cf2644b-4b0b-428f-9387-6d876050dc67).
[    6.083414] Using s2idle quirk to avoid T14 Gen2 AMD platform firmware bug
[    6.204406] platform regulatory.0: Direct firmware load for regulatory.db failed with error -2
[    6.461984] mt7921e: unknown parameter 'fw_name' ignored
[    6.461988] mt7921e: unknown parameter 'wmfw_name' ignored
[    6.462075] mt7921e 0000:03:00.0: enabling device (0000 -> 0002)
[    6.463812] mt7921e 0000:03:00.0: disabling ASPM  L1
[    6.470444] mt7921e 0000:03:00.0: ASIC revision: 79610010
[    6.550653] mt7921e 0000:03:00.0: HW/SW Version: 0x8a108a10, Build Time: 20250625153620a
[    6.562272] mt7921e 0000:03:00.0: WM Firmware Version: ____010000, Build Time: 20250625153703
[    7.399150] mt7921e 0000:03:00.0 wlp3s0: renamed from wlan0
[    7.776550] psmouse serio2: trackpoint: Elan TrackPoint firmware: 0x12, buttons: 3/3