docs(tech): add PM9A1 firmware changelog GXA7401Q to GXA7802Q

- Document full firmware progression: GXA7401Q → GXA7602Q → GXA7702Q → GXA7802Q
- GXA7802Q fixes unmap/TRIM handling regressions from GXA7702Q
- Add sources: Samsung PDF, Win-Raid, GitHub samsung-nvme-firmware

docs/tech/firmware-update-research.md

@@ -51,7 +51,20 @@ last_updated: '2026-04-02'
 | **Latest** | **GXA7802Q** |
 | Source | [OVHCloud Firmware Guide](https://support.us.ovhcloud.com/hc/en-us/articles/22361371147923-Advance-Dedicated-Servers-Upgrading-Your-Samsung-NVMe-PM9A1-Firmware) |
 
-**Status**: **Update available.** GXA7802Q is newer than GXA7401Q. Improves performance, stability, and security.
+**Status**: **Update available.** GXA7802Q is newer than GXA7401Q. Fixes unmap handling issues introduced in GXA7702Q.
+
+### Firmware Changelog (GXA7401Q → GXA7802Q)
+
+| Version | Key Changes |
+|---------|-------------|
+| **GXA7401Q** (current) | Fixed Pyrite spec violation (prevented user data erase during TCG revert). Improved write performance drop beyond 70% capacity usage via foreground GC in SSB area. |
+| **GXA7602Q** | Changed LPN per Unmap Range from total device LPN to 1000. Improved free block generation, reduced unnecessary migrations and TLC writes. |
+| **GXA7702Q** | Increased LPN per Unmap Range to 10,000. Introduced **side effects**: lengthened FW time for Unmap operations, slower free block generation, increased unnecessary migrations. Samsung recommended **holding** this version. |
+| **GXA7802Q** (latest) | **Fixes all GXA7702Q side effects.** Corrects unmap handling, restores free block generation performance. Released ~Nov 2022 after internal qualification. Overall stability and performance improvements. |
+
+**Key benefit for workstation**: The GXA7401Q → GXA7802Q jump fixes unmap/TRIM performance regression chain from GXA7702Q intermediate versions. Since this is a root NVMe drive with heavy I/O, improved unmap handling and write stability are relevant.
+
+**Note**: No official Samsung changelog exists publicly. Information sourced from Samsung internal PDF (gzhls.at), OVHCloud deployment guide, and Win-Raid community.
 
 **Update procedure** (Linux, no Samsung Magician needed):
 
@@ -262,4 +275,7 @@ fwupdmgr update           # Apply available updates
 - [Samsung SSD Firmware Tools](https://semiconductor.samsung.com/consumer-storage/support/tools/)
 - [NVIDIA Drivers](https://www.nvidia.com/en-us/drivers/)
 - [Jabra Xpress for Linux](https://www.jabra.com/support/release-notes/release-note-jabra-xpress-for-linux)
-- [linux-firmware.git](https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git)
+- [linux-firmware.git](https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git)
+- [Samsung PM9A1 Firmware PDF (gzhls.at)](https://gzhls.at/blob/ldb/1/a/2/a/90ce739915b765d7fdae4620177253f0056e.pdf)
+- [Win-Raid PM9A1 Discussion](https://winraid.level1techs.com/t/samsung-pm9a1-firmware-update/37242)
+- [GitHub: samsung-nvme-firmware issues](https://github.com/lolyinseo/samsung-nvme-firmware/issues/10)