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[Q] eMMC crash - possible reasons and solutions

28th November 2011, 07:03 PM   |  #1  
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Hello everyone.

I've been looking around here for some time, reading all that suff about eMMC chips burning on Desire S. That fact dissapoints me as I was aiming to buy the gadget myself. However, I didn't find any general solution or even investigation of the case, so I'm trying to develop some kinda stuff. Let me summarize main points that we have so far.

1) The faulty guy is usually Samsung eMMC-type BGA chip KLM4G2DE (2 Gb NAND flash), however Sundisk chips were also found to burn.
2) The problem is rather hardware than software dependent as it is observed without any corellation to hboot/flash installed.
3) It was noticed that in many cases eMMC fault followed extraction-insertion of battery after phone freeze.
4) HTC doesn't recognize this as defective case and no improvements to hardware are made in new revisions of motherboard (MB) as there have been cases (at least one) when the same phone after warranty repair crashed again after some time.with the same eMMc chip installed
5) Other phones with the same eMMC installed (e.g. Sensation) doesn't experience same problems.

What can I deduce out of all this stuff and my own experience?
As soons as the case seems to be non-software dependent it should be the chip or some other hardware that drives it wrong. As soons as the chip itself seems to be OK (see 5) I beleive that it is poor motherboard design that burns the chip down. eMMC is rather bomb-proof architecture combining the memory itself and the memory controller on the same crystal. Two major ways to drive it wrong are:

1) Supply incorrect clock pulses to clock bus
2) Supply incorrect power (current/voltage/voltage slope) to memory and/or controller

The first assumption seems not very possible as clock usually comes from centralized source controlled by oscillator. If the clock is wrong, the emmc fault wouldn't be the only problem
The second point seems rather reasonable as Samsung eMMC power-up guide (see file attached) directly points out the importance of accurate power supply (especially power-on slope!), otherwise memory faults are inevitable.

That's all I can deduce so far, unfortunately there's no photos/schematics of desire s on the web to analyze the connection of emcc chip to MB. What can I suggest to prove/disprove all the stuff I wrote:

1) Can someone brave disassemble his Desire S and make high resolution photos of both sides of motherboard? This may help in further analysis.

2) Can someone even more brave and being on close terms with oscilloscope try to measure power-up voltage slope on Vсс and VccQ inputs of eMMC chip(see document attached) ? May be we are just having one of the issues described in the document.

UPDATE
I found the datasheet four our chip, find it attached to this post
Attached Files
File Type: pdf eMMC_app_note_for_Power_up_rev0.pdf - [Click for QR Code] (150.1 KB, 300 views)
File Type: zip KLMxGxxE.zip - [Click for QR Code] (317.6 KB, 188 views)
Last edited by levantine; 28th November 2011 at 07:51 PM. Reason: Datasheet attached
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28th November 2011, 07:21 PM   |  #2  
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Also, strangely, a common way to trigger the 'dead emmc' is when you hit 'update all' apps in the android market, regardless of what ROM/market version your on..

Surely it must be a combination of a software fault/problem too?
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28th November 2011, 07:25 PM   |  #3  
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As far as I got it, some kinda software problem causes phone to hang during market update. Lots of users tend to solve this by removing/re-inserting the battery which leads to burned emmc.
28th November 2011, 07:38 PM   |  #4  
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Yeah.. that would be the case. It kind of sucks knowing you could potentially brick your phone by just updating apps from the market.

And if you're on a custom ROM, you're screwed

Sent from my HTC Desire S using xda premium
29th November 2011, 11:39 AM   |  #5  
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From my experience the eMMC in the "fried" cases is not actually faulty but simply does not allowing write access. Usually it is accompanied by /cache or /cache + /data corruption. When only /cache is the problem it is fixable, but when /data is affected there is no way to write a bit on the internal memory.

Unfortunately I have no confirmed explanation to this...

Just in theory when updating several apps from the Market (or other activities requiring use of /cache partition) it is possible that the /cache is filled with data and the device stucks at a point when it has no more space available to write. Rebooting to recovery and wiping /cache solves the problem. But if in that moment, when the app is downloading to /cache and another app is written from /cache to the /data partition at the same time, disconnecting the power source (battery pull) can interrupt the process making this partition unavailable (example: if you take out your USB flash drive from the PC while writing data on it there is a great chance to destroy it - tested myself ) The ext4 file system provides a protection for such cases by the way it is managing the writing process - reference here.

In my opinion all of the bricked devices (famous "fried eMMC") reported in this forum are easily repairable with JTAG and a skilled technician, but unfortunately there are no such cases reported here. Personally I do not have the knowledge, equipment and intention to do such experiments myself.

This is my logic based on my observations while trying to assist people in this forum to solve this issue. For some of them it was successful, for others - not.

I hope that my post will make a contribution to the general picture.

Regards,
Stefan
Last edited by amidabuddha; 29th November 2011 at 04:01 PM.
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29th November 2011, 12:42 PM   |  #6  
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Quote:
Originally Posted by amidabuddha

The ext4 file system provides a protection for such cases by the way it is managing the writing process.

Hi, thanks for sharing your thoughts. So you say those who uses EXT4 should be safe? Here's a screenie from my wifes DS.



Also, my SGSII got broken and now i'm thinking to get one of Desire S for myself. How's situation with those fried eMMC's, was there a lot of reports over here? What chances are to get it "fried"? Sorry, i don't have much time to go trough all DS forums.
29th November 2011, 02:35 PM   |  #7  
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Isn't Gingerbread ext4?
29th November 2011, 03:21 PM   |  #8  
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Quote:
Originally Posted by al89nut

Isn't Gingerbread ext4?

At the present moment I think that HTC switched to ext4, at least when looking the update_script of the new OTA 2.10.401.8:

Code:
# Script Version: G2.3

mount("ext4", "EMMC", "system", "/system");
mount("ext4", "EMMC", "/dev/block/mmcblk0p28", "/system/lib");
...
mount("ext4", "EMMC", "userdata", "/data");
EDIT: after checking my current file system (Stock 2.10.401.8) it appeared that all partitions (system, data, cache and devlog) are ext4

but when I purchased my device with version 1.28.401.1 and got the guts to S-OFF it (at the end of July) all my partitions were ext3 and I converted them manually using 4EXT Recovery. Maybe flashing a custom ROM converted the partitions from ext4 to ext3 I do not know...

I am not claiming 100 % accuracy in this information, but Revolutionary supports only hboot 0.98.0000 (from version 1.28.401.1) and hboot 0.98.0002 (version 1.47.401.4) so I suppose the most of the fault cases around are users like me that S-OFFed with ext3 but most of them that faced this problem had the ClockworkMod recovery (flashed by the Revolutionary exploit) which was not offering file system conversion at that time (not sure about the latest versions) and never converted as I did.

Cannot say for sure also for the Stock users that prefer to send the device for repair after failure with Market updates instead of making a mess with custom recoveries and RUU flashing. Maybe is this case a /cache wipe will do the trick (BTW the Stock recovery has an option "wipe cache")...or like this guy that fixed it with a hard reset and a new SDcard.

More or less the fact that the new version of the Market is updating the apps one by one and has a button to stop all updates at once is made by a reason...
Last edited by amidabuddha; 29th November 2011 at 04:45 PM.
29th November 2011, 03:38 PM   |  #9  
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Quote:
Originally Posted by al89nut

Isn't Gingerbread ext4?

My wife's DS originally had:

system - EXT4
data - EXT3
cache - EXT3

The phone was purchased 3-4 months ago and had 1.28.401.1 firmware on it if i recall correctly. BTW, she got famous M4G2DE chip...
Last edited by MS.; 29th November 2011 at 03:46 PM.
29th November 2011, 11:11 PM   |  #10  
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So does the ext4 update mean the problem is fixed? Not that I want to experiment

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