[SOLVED] SDHC card not always "partitioned" BusyBox Kernel 2.6.37 IPNC

Mechi · 04-05-2017, 03:00 AM

Hi,
I'm using IPNC_RDK 3.8.0 with kernel 2.6.37 on a proprietary IP camera board.
Until recently, when the kernel comes up, I get:

mmc1: new high speed SDHC card at address aaaa
mmcblk0: mmc1:aaaa SC32G 29.7 GiB
mmcblk0: p1

With the same SDHC card, I started getting the message:

mmc1: new high speed SDHC card at address aaaa
mmcblk0: mmc1:aaaa SC32G 29.7 GiB
mmcblk0: unknown partition table

We only work with MSDOS partitions and I found the place in the kernel where the partition place is checked.
kernel/fs/partitions/msdos.c (or /block/partitions/msdos.c in later versions)

After printing out where it fails, I've narrowed the error to:

#define MSDOS_LABEL_MAGIC1 0x55
#define MSDOS_LABEL_MAGIC2 0xAA

static inline int
msdos_magic_present(unsigned char *p)
{
return (p[0] == MSDOS_LABEL_MAGIC1 && p[1] == MSDOS_LABEL_MAGIC2);
}

What I can't figure out is why the same microSD card (32G) sometimes is OK and sometimes isn't - even without formatting, etc.
Is there anything that I can do to ensure that the partition table will always be OK?
The same SD card, when opened in Windows shows *.avi files that were recorded by the IP camera and they can be played back.

Any help on this would be greatly appreciated.
Thanks,
Mechi

Mechi · 04-05-2017, 03:47 AM

I'm going to comment out the check of 0x55 0xAA - the "magic number".
I hope this is OK...

Mechi · 04-06-2017, 03:01 AM

I inadvertently made a change in the dma.h file and seems to have caused the problem.

Lesson learned -

SD card uses DMA for reading
When looking for an error - first look at what changes YOU made
Don't make changes unless you're 100% sure they're necessary. I thought it was a buggy definition, so I changed something and introduced a REAL bug.

Closing this thread...