BBB eMMC setup failure

[Edu Galvez]

I'm investigating a BBB unit that got stuck during power-up. Only power led, and no data through console.

Rebooting or powering from USB or plug didn't help.

It was recovered after re-flashing the eMMC

fdisk and write-tests on the MMC shown no failures.

After thousand of powr cycle tests, I managed to repeat a "weird" situation once again. Booting from SD, the MMC appears not properly configured. I can mount the MMC, but it is empty. I don't know what caused that issue. I've been re-flashing the unit many times, and suddenly, it noticed the issue.

I only managed to recover the unit after re-flashing again. Rebboting/cycling the power didn't worked. The environment is noise free, and power supply is stable

I got the MMC registers (/sys/kernel/debug/mmc1) during the fail scenario:

Working scenario:

clock:          52000000 Hz

vdd:            7 (1.65 - 1.95 V)

bus mode:       2 (push-pull)

chip select:    0 (don't care)

power mode:     2 (on)

bus width:      3 (8 bits)

timing spec:    1 (mmc high-speed)

signal voltage: 0 (3.30 V)

regs:

CON:            0x00000620

HCTL:           0x00000b04

Failing scenario:

clock:          52000000 Hz

vdd:            21 (3.3 ~ 3.4 V)

bus mode:       2 (push-pull)

chip select:    0 (don't care)

power mode:     2 (on)

bus width:      3 (8 bits)

timing spec:    1 (mmc high-speed)

signal voltage: 0 (3.30 V)

regs:

CON:            0x00008620

HCTL:           0x00000d00

It is suposed that u-boot/kernel setup the MMC host based on MMC data durind start-up. So I guess this kind of failure is hardware related.

Any ideas?

Thanks!