trouble with should-be-bootable SD cards and kernel versions

[AJ ONeal]

I have a few inter-related issues:

• Why would one kernel boot a card that another kernel can't?
• Why would a card's disk geometry matter for boot?
• Who is a good manufacturer for getting hardware-identical cards in bulk?
• How can I probe the actual "disk geometry" of an sd card?

I bought 100 Transcend SD cards a little while ago and duplicated them with an OpenEmbedded-based filesystem (linux-2.6.36).

There were a few "bad" cards that I threw out, but the success rate was acceptable.

In the next round of 40 SD cards I used a Linaro-based filesystem (linux-2.6.39) and had about a 50% failure rate when testing that the cards would boot, which is absurd.

There kernel reports: [    1.003204]  mmcblk0: unknown partition table

However, the cards would mount and show files just fine.

I reduplicated one of the non-booting cards with an OpenEmbedded filesystem and then it booted. Weird!

After some investigation I found that using `gparted` (instead of `fdisk`) to create a new partition table and then `rsync`ing the contents of the original filesystem resulted in a booting Linaro card.

Rinse and repeat and I ended up with 3 images which only vary by the disk geometry as reported by `fdisk -l`:

• 50% -- 255 heads, 63 sectors/track, 974 cylinders
• 40% -- 2 heads, 4 sectors/track, 1957632 cylinders
• 10% -- 247 heads, 62 sectors/track, 1022 cylinders
• 1 card still didn't boot

I'm lost. Please advise.

AJ ONeal

Non-booting kernel message

[    0.923309] Waiting for root device /dev/mmcblk0p2...

[    0.957885] mmc0: host does not support reading read-only switch. assuming write-enable.

[    0.982025] mmc0: new high speed SDHC card at address b368

[    0.988494] mmcblk0: mmc0:b368 USD   7.46 GiB 

[    0.993957] mmcblk0: detected capacity change from 0 to 8018460672

[    1.003204]  mmcblk0: unknown partition table

[    1.036926] VFS: Cannot open root device "mmcblk0p2" or unknown-block(179,2)

[    1.044433] Please append a correct "root=" boot option; here are the available partitions:

[    1.053344] b300         7830528 mmcblk0  driver: mmcblk

[    1.058959] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(179,2)

Booting kernel message

[    1.122070] mmc0: host does not support reading read-only switch. assuming write-enable.

[    1.146087] mmc0: new high speed SDHC card at address b368

[    1.152557] mmcblk0: mmc0:b368 USD   7.46 GiB 

[    1.158020] mmcblk0: detected capacity change from 0 to 8018460672

[    1.166351]  mmcblk0: p1 p2 p3

[    1.259674] EXT3-fs: barriers not enabled

[    1.265411] kjournald starting.  Commit interval 5 seconds

[    1.271331] EXT3-fs (mmcblk0p2): mounted filesystem with ordered data mode

[    1.278686] VFS: Mounted root (ext3 filesystem) readonly on device 179:2.

[Brad Midgley]

you should compare notes with Steve Sakoman.

http://www.sakoman.com/OMAP/microsd-card-perfomance-test-results.html

--
Brad Midgley

[AJ ONeal]

Confirmed: the combination of a linaro-2.6.39 kernel with a transcend 8gb card results in flakey boots.

• linaro-2.6.39 kernel is affected
• transcend cards are affected
• oe-2.6.36 kernel is not affected
• sandisk 8gb cards are not affected (67 megabytes smaller)

I zero'd a card, but instead of only zeros, I also wrote the sector number in each 512-byte block.

I changed the kernel to print out the 512 bytes it read as the mbr to the screen.

When the card didn't boot fully the printk showed all zeros except for a sector number about 100mb into the card.

How weird! Hardware? Kernel?

Anyway, today my sandisk cards arrived and all 10 of them worked flawlessly.

I ordered another 50 and hope to see the same results.

AJ ONeal

On Wed, Jun 29, 2011 at 11:48 AM, AJ ONeal <cool...@gmail.com> wrote:

[Bryan Murdock]

On Thu, Jul 7, 2011 at 4:37 PM, AJ ONeal <cool...@gmail.com> wrote:
> Confirmed: the combination of a linaro-2.6.39 kernel with a transcend 8gb
> card results in flakey boots.
>
> linaro-2.6.39 kernel is affected
> transcend cards are affected
> oe-2.6.36 kernel is not affected
> sandisk 8gb cards are not affected (67 megabytes smaller)
>
> I zero'd a card, but instead of only zeros, I also wrote the sector number
> in each 512-byte block.
> I changed the kernel to print out the 512 bytes it read as the mbr to the
> screen.
> When the card didn't boot fully the printk showed all zeros except for a
> sector number about 100mb into the card.
>
> How weird! Hardware? Kernel?

I don't know, raw nand flash is pretty junky stuff. It's not strange
at all for there to be bit errors and bad blocks. Maybe that's what
you are seeing.

Bryan