BCMmodule
commented
7 years ago Tomaž,
Thank you for your detailed description. Using a standard BeagleCore BCS1 or alike with BCM1 we do not see these issues. We would need to know about the custom baseboard of yours in detail and the software-set you are running, maybe even a prototype for testing in order to provide more qualified information.
By the way: We have almost simultaneously received a very similar request by one of your colleagues via email. The datasheet for eMMC by SK Hynix is not easy to obtain and we are not allowed to publish it here (SK hynix 1xnm_32Gb based 4GB_Rev1 0.pdf). We have emailed it to your colleague on Friday.
Hope this helps.
avian2
cml12
urbangregorc
stephanecharette
christianhalter
Hi
We have designed a custom board around the BCM1 module. 2 out of 3 prototypes we made so far are suffering from intermittent problems with the on-board eMMC. These problems manifest themselves when using eMMC (
mmcblk1) as the Linux root filesystem, apparently at random. We see kernel messages like the following on the serial console. When this happens, all eMMC operations result in errors and the board does not recover on its own. Normal operation is only resumed after a power cycle.The affected boards will sometimes also not boot after a power cycle. In that case, only a series of
CCCCCcharacters is seen on the serial console (no normal bootloader messages). For the two affected boards, this happens approximately once per day. The third board has been running continuously for many days without encountering this problem.At the moment we cannot reliably reproduce the problem in testing. Loading the CPU, eMMC and SD card interfaces does not seem to trigger the problem. After a power cycle, extensively testing the eMMC flash with
badblocks(read-only and r/w tests) does not find any failures.We are using the
4.4.30-ti-r64kernel and a userland based on thebone-debian-8.6-seeed-iot-armhf-2016-11-06-4gb.imgimage. We use a custom device tree. However the fact that these boards will occasionally not reach the bootloader stage suggests that this is not a problem with the Linux system.We found similar problems to what we are experiencing described here (a custom AM335x-based system) and here (BeagleBone Black). The first discussion suggests that the cause is a hardware problem on the MMC bus, however they are using an SD card and the reported card status number is different.
We don't rule out a problem with our hardware design. However the connection between the AM335x and MMC flash runs on the BCM1 module. We don't currently see any way how a fault in our design could cause these symptoms. We suspected the power supply but we see no immediately apparent problems. However we couldn't find the datasheet for the specific Hynix eMMC flash IC used on BCM1 so we can't say for sure the supply voltage variations we see are in spec.
We would appreciate any help with this issue.