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Linux - Embedded & Single-board computer This forum is for the discussion of Linux on both embedded devices and single-board computers (such as the Raspberry Pi, BeagleBoard and PandaBoard). Discussions involving Arduino, plug computers and other micro-controller like devices are also welcome.

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Old 01-04-2013, 04:49 PM   #1
dpdonny
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Registered: Nov 2012
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JFFS2 Garbage Collection causing mtd do_write_buffer timeouts?


Greetings,

My first post...so be kind.

Some data:
----------
- proprietary board with ARM processor booting out of NOR flash
- Linux kernel 3.1.0
- BusyBox v1.19.v
- JFFS2 mounted mtdblocks
- using JFFS2 for disk-like storage of images; not using JFFS2 for
root file system (that's in RAM)

SUMMARY
-------
I am seeing intermittent mtd do_write_buffer() timeouts when un'taring a large file (10MB) directly to flash and believe the cause to be a mutex issue with jffs2 garbage collection daemon.

DETAILS
-------
Flash status returned in chip_ready() (cfi_cmdset_0002.c) when the timeouts occur indicate "Erase in progress" (DQ3=1, DQ2 toggling, DQ6 toggling), which shouldn't be the case when writing the flash. My guess is there is a mutex issue occurring with the jffs2_gcd_mtdX when it's erasing a block it recently collected.

I've killed the gcd thread and am currently re-running my test. I've yet to see a timeout.

QUESTIONS
---------
Would jffs2 garbage collection erase contend with a write operation (especially when the write is large and takes a while)?

So should garbage collection be turned off when doing large writes to flash?

Thanks for reading this far...
 
  


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