i have a SSDed ipod classic.i keep getting panic error of disk write. sometime its "dc_writeback_callback() - Could not write sector xxxx",sometimes its other error.
it happens several times per hour while listening music.and happens almost every time i unplug usb cable.
it also freezes about one time per hour,without any error shown on screen,usually happens after i pressed some button.
(my ipod also freeze after i play some ape with compress level larger than 4000, but this is as expected,since the limitation of cpu peformance,https://www.rockbox.org/wiki/CodecPerformanceComparison.the freezed i mentioned above doesnt include this kind of freeze )
it also happened one time that i keep getting panic error of dc_writeback_callback and could not log into rockbox ,nor could i connect it to computer and use the disk mode .i thought my ssd was dead. but it wasnt.after i flashed the apple official firmware and format my ssd and reflash rockbox.it works again.
looks very like a disk driver issue.
i read it on the forum that the disk driver of ipod is reverse-engineered from an old official firmware of apple and its not designed for ssd,so rockbox doesnt work well on SSDed device.(sorry i cant find the link at the moment)
i modified source code and made a custom build.https://drive.google.com/file/d/0B3ow0cQpIx1famljZy1Hanp6UEE
i doubled the long int "ata_sleep_timeout" and doubled timeout value of every usage of “TIMEOUT_EXPIRED" marco in firmware/target/arm/s5l8702/ipod6g/storage_ata-ipod6g.c。
i also disabled support of ape with compress level of 4000 and 5000 by the way by modificating lib/rbcodec/codecs/demac/libdemac/parser.c,bc ipod6g cant really play them in real time,all you can get from them is just intermittent sound and a freezed device...
after using this build,problem solved(at least on my device).my device had been running for 11hours before it freeze,no panic error any more,it eventually freezed though,but much more stable.
if this build also solves your problem,leave a message plz.if this is useful for many people,maybe we can merge the change into official build.