RTOS/AM3352: eMMC write timeout

Hi,

When you run the RTOS MMCSD example on MMC1 (EMMC), do you use the same HW attribute as in MMCSD_v1_HwAttrs MMCSDInitCfg[MMCSD_CNT] in the pdk_am335x_1_0_14\packages\ti\drv\mmcsd\soc\am335x\MMCSD_soc.c? Do you have 8-bit interface?

Regards, Eric

The official examples has "pdk_am335x_1_0_14\packages\ti\drv\mmcsd\soc\am335x\MMCSD_soc.c" linked into project, the MMCSDInitCfg settings are reserved without any changes made. When the error occur, register SD_STAT has value of '0x18010', the most bit 1 (CTO) indicates no response is received for this command(cmd25).  While I tried each time MMCSD_write with 512B, the bitrates becomes very slow(about 233KBps), it kept running over 12 hours without any errors, but the bitrates are too slow to meet customers requirment.

Hi,

What is the eMMC clock frequency you are using? Can you try to keep the same block size 8KB or 2MB but reduce the clock frequency? What eMMC chip are you using on MMC1?

It sounds like a timing issue to me. The answers to the above questions may help us to pin-point the root cause.

Ming 

Sorry for late reply. 

Our customized board has a 'MTFC64GJVDN-4M IT' eMMC chip soldered, in 8-bit mode (MMC1_DAT0 ~ MMC1_DAT7), with capacity 64GB. The initial of eMMC is in source 'pdk\packages\ti\drv\mmcsd\src\v1\MMCSD_v1.c' . In the function MMCSD_v1_initEmmc(), it read out capacity information from the eMMC chip, then set MMC controller in 8-bit mode, and supply 26MHz clock. I tried to set the clock up to 52MHz or down to 20MHz, but the random fail were still there. It looks like to be a timing issue, but I can't find out where to adjust the timing settings (other than clock and bus width). By decreasing the frequency of CPU, modifying the timeout setting of MMC (HSMMCSDSetDataTimeout), changing timeout setting of fatfs, ...  after dozens of such tests, the error is still there.

[1]

While I am still in confusing how the timeout raised, I get a way to fix it. In source 'MMCSD_drv.c', when MMCSD_write or MMCSD_read return error, a recover function will be called, then re-submit the failed request of write/read .

MMCSD_recover()

{

MMCSD_close();

MMCSD_open(handle);

}
When the write/read failed, a recover is scheduled, then the next re-write/re-read always succeed. After the whole capacity (64GB) were written, dozens of this fix were scheduled. I think its the SOFTRESET and initialization in open fixed the error.  Then I added fatfs and made test with writing files, everything become OK.

[2]

While trying to added format function, I found a bug in f_mkfs (packages\ti\fs\fatfs\src). 

if (n_vol < 0x10000) {

st_word(tbl + BPB_TotSec16, (WORD)n_vol);

} else {

- st_word(tbl + BPB_TotSec32, (WORD)n_vol);

+ st_word(tbl +BPB_TotalSec32, (DWORD)n_vol);

}

After applied this fix, you can successfully format the eMMC partition in FAT32 format and then mount it for file operations. No more ways are needed (recommend in other posts such as connect to PC via USB and format it on PC).