Let BeagleBone Bootloader read from eMMC instead of SD-/MMC-Card

qxc

The Bootloader for Beaglebone that comes with Starterware is able to load a "app" file from external SD-Card (MMC0 lines of CPU). Since BeagleBone Black there exists a second storage eMMC (which is connected to MMC1 lines).

Now I tried to modify the Bootloder sources to let MLO read from eMMC but failed miserably. That's what I have changed:

- changed MMC0-base-address and MMC0-register and constant names to MMC1 in all relevant sources (like SOC_MMCHS_0_REGS to SOC_MMCHS_1_REGS)

- modified HSMMCSDImageCopy() to load file from "1:\app" to get drive 1

- fixed the assignment bug in HSMMCSDFsMount() to use fat_devices[driveNum] instead of fat_devices[0]

- mount drive 1 prior to accessing FAT-FS

- modified functions in fat_mmcsd.c to allow access of drive 1 and 0 (instead of 0 only)

Nevertheless eMMC - which of course contains a FAT-FS partition - is not accessible. Any ideas what could be missing here?

over 12 years ago

0 Ralf Roesch over 12 years ago

Prodigy 100 points

Just a thought. May be you should check also the registers content beside the name (offset). For example the BBB MMC1 is used in 8bit mode, where MMC0 (SD card) is not.

0 Ramesh Dandamudi over 12 years ago

TI__Intellectual 1480 points

Hi,

Latest StarterWare release doesnot support eMMC.

Changes are required in mmcsdlib to support eMMC.

Regards,

Ramesh D

0 qxc over 12 years ago in reply to Ramesh Dandamudi

Genius 5820 points

@Ralf: you are right, the 8 bit mode was missing. But that doesn't seem to be the only thing, it is still not working...

Ramesh Dandamudi said:
Changes are required in mmcsdlib to support eMMC.

@Rames: OK, and WHAT changes are required there exactly?

Thanks!

0 Ralf Roesch over 12 years ago in reply to qxc

Prodigy 100 points

Hans, did you set up the PIN MUX for MMC0 correctly?
Maybe you have to tune timing and mode registers too?
regards
Ralf

0 qxc over 12 years ago in reply to Ralf Roesch

Genius 5820 points

PIN MUX is set correctly but...

Ralf Roesch said:
Maybe you have to tune timing and mode registers too?

...which registers do you mean exactly with this?

0 Ralf Roesch over 12 years ago in reply to qxc

Prodigy 100 points

Good Morning Hans, I meant registers which are mentioned in chapter 18.5 of AM335x Technical Reference Manual.
For example SD_HCTL, field BTW. Do you follow 18.4.2 MMC/SD/SDIO Controller Initialization Flow?

0 qxc over 12 years ago in reply to Ralf Roesch

Genius 5820 points

Controller initialisation flow is as described. For other initialisation I'm using the same values like for external Sd-Card (MMC0). May be the voltage settings are different for eMMC (MMC1)?

0 Ralf Roesch over 12 years ago in reply to qxc

Prodigy 100 points

Voltage setting might be an issue, see:
http://lxr.free-electrons.com/source/drivers/mmc/host/omap_hsmmc.c#L1091
The setup seems not to be very trivial. I think the MMC device index index enumeration starts with index 1.

One more suggestion from my side: you could boot a Linux kernel on your BeagleBone, mount your SD card and peek the interesting register values.

Is your FAT partition still valid (probably you made a lot of tests in between)?

0 qxc over 12 years ago in reply to Ralf Roesch

Genius 5820 points

OK, I made a step forward: it seems the voltage the eMMC is accessed with is still wrong. From what I found in the hardware spec it seems it has to be driven wiht a bus voltage of 3.3 V.

So I'm stumbling upon the next problem: which of the funny constants (SD_OCR_VDD_3P0_3P1, SD_OCR_VDD_3P1_3P2, SD_OCR_VDD_3P2_3P3, ...) specifies 3.3 V?

Thanks!

PS: Yes, the FAT-partition is still valid, when I boot a Linxu system from external SD-card it is recognised properly.

0 Ralf Roesch over 12 years ago in reply to qxc

Prodigy 100 points

Looking at a Micro SD card data sheet you will find some answer.
I would assume for a a 3.3V capable SD card bits
20 (SD_OCR_VDD_3P2_3P3) and
21 (SD_OCR_VDD_3P3_3P4)
should be set. This selects a voltage range from 3.2V to 3.4V.

Processors

Processors forum

Let BeagleBone Bootloader read from eMMC instead of SD-/MMC-Card