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

[LEDE Bugs]

The following task has a new comment added:

FS#1242 - SATA broken on kernel 4.9 on mt7621
User who did this - easyteacher (easyteacher)

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[[https://events.static.linuxfound.org/sites/events/files/slides/Shuah_Khan_dma_map_error.pdf|Detecting silent data corruptionsand memory leaks using DMA Debug API]]

I found a document possibly related to the bug. To debug, set CONFIG_DMA_API_DEBUG=y. Currently I have no idea how to use it.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1242#comment4234