[share]custom rockbox build for SSDed ipod6g(classic)

[r4bbit]

background:
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)

solution:
i modified source code and made a custom build.
https://drive.google.com/file/d/0B3ow0cQpIx1famljZy1Hanp6UEE

https://github.com/wangyu-/rockbox-modified (new link as in 2024)

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.

[__builtin]

Hi, and welcome to the forums.

I see that you've provided a modified build, which is fine, but you haven't provided the source which it was built from. Can you please provide a link to it?

__builtin

[r4bbit]

Hi, and welcome to the forums.

I see that you've provided a modified build, which is fine, but you haven't provided the source which it was built from. Can you please provide a link to it?

__builtin

hi,__builtin. thx and thx for reminder.

the code i modified was base on the latest master branch cloned a few days ago from https://github.com/Rockbox/rockbox.git

code version(last commit id):
eaf6aad690927ab0abfaae5276ef6561b334f803

patch of my modification:
https://drive.google.com/open?id=0B3ow0cQpIx1fUi1BVGRmeUIwNEU

https://github.com/wangyu-/rockbox-modified/commits/master/ (new link as in 2024)

[Massa]

Hmm, I don't get it - why does doubling a timeout value make it more reliable for SSDs?
Aren't SSD faster than HDs and therefore shouldn't need longer timeouts? 

I'm confused!

[saratoga]

His SSD is probably not made for use in a DAP that will go 30 minutes at a time without accessing it, so it probably powers off and has to reboot when he access it again.  The stock hard drives are made to work for portable devices so they are always ready to talk to the host. 

[r4bbit]

His SSD is probably not made for use in a DAP that will go 30 minutes at a time without accessing it, so it probably powers off and has to reboot when he access it again.  The stock hard drives are made to work for portable devices so they are always ready to talk to the host.

this is not the case.the disk failure happens pretty randomly.it may happen in 30 seconds after i powered on my device.

Hmm, I don't get it - why does doubling a timeout value make it more reliable for SSDs?
Aren't SSD faster than HDs and therefore shouldn't need longer timeouts? 

I'm confused!

yes,the overall speed of ssd is almost always faster than hdd.no matter compared by 4k random write or by sequence write.but a disk write consists a few micro operation at lower level.

i assume at driver level there should be two mirco operations: 1.seek for a track.   2.write data to track , each of them has its own timeout value.

the seeking operation of ssd should be much faster than hdd and will never timeout. the write operation of ssd may be slower,because of the "write amplification" effect of writting a nand and the "wear leveling" work of the ssd's chip.

there is a ssd 4k random write latency test picture in attachment,its not tested on my ssd,its from internet.the highest latency of a 4k write can be 30ms when the ssd is 75% filled,and it become worse after 100% filled,as high as 40 ms.the seeking time of ssd is about 0.1ms,so you can ingore the seek time and consider the overall time as the time of doing write.

for hdd,after the track has been seeked,the write latency shouldnt be higher than spinning a round(which is 60min/4200RPM=14.3ms).

i m not an expert of disk driver. i was just analyzing

[prof_wolfff]

There are situations where writing a sector to a SDD takes more time, it is depending on the wearing algorithms and the block size of the SDD, i.e. when writing a sector requires to reallocate other sectors, or when there are free sectors but they are not erased, then the SDD FW needs to erase a whole block before writing this sector. It is supposed that the SDD FW will do these operations on background when the SDD is idle but not always is possible to do that way, or the FW algorithms are not good enough.

[clembo]

I have an Ipod 4G with the exact same type of behaviors when using an SD card as r4bbit has on his Ipod 6G.

Long/short.  I have a working 32GB Adata CF card that works fantastic; it's connected via a CF to Mini IDE.  I was very careful to make sure it emulated a hard drive.  Later on I picked up 2 additional Ipod 4G's, did the same process only change is that I decided to experiment with a CF to SD adapter instead of a CF card.  This is where I ran into errors; tried multiple different storage sizes/speeds and got the same result.  I suppose there are a few different approaches that one could take, but I'd rather use an SD card (much more convenient and cheaper than CF).

I can restore the Ipod, install  play/stop music using Itunes on the Ipods.  I can install and load rockbox w/out issue.  The trouble starts when attempting to write to the SD card while in Rockbox.  To duplicate, I attempted to save the CFG file within settings.  It takes a long time to write and then errors out with a kernel panic.

Here's a copy of the error message:

Panic
sc_writeback_callback ()_ could not write sector 152315 (error -4)
pc:0006504C sp:400B930
A:00073868
BT end

@r4bbit
I'm going to try the same approach you did and see if that resolves the write issue.