[FS#1242] SATA broken on kernel 4.9 on mt7621

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - neheb (neheb) 

Attached to Project - LEDE Project
Summary - SATA broken on kernel 4.9 on mt7621
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - Supply the following if possible:
 - Device problem occurs on - GnuBee Personal Cloud One
 - Software versions of LEDE release, packages, etc. - latest trunk
 - Steps to reproduce - Run trunk for a few hours and verify that the data on the hard drive is legitimate.

Basically, with kernel 4.9 there's some weird issue where after several hours (around 18), the SATA controller starts returning bad data. On 4.4, this is not a problem.

I've avoided reporting this problem to kernel.org since ramips is quite LEDE specific. Could be a pcie issue for all I know.

The data on the actual hard drive is fine. It's just bad data that's being returned. Maybe bit errors or something.

The way I test this is by using transmission with its Verify feature. Last I tested with adm + ext4, a torrent that verified at 100% verified at 91% 3 days later.

btrfs is more vocal since it reports silent data corruption and throws checksum mismatch errors in dmesg quite frequently after a few hours.

I currently work around the issue by running kernel 4.4, but this is not a long term solution.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1242