• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 100 subscribers
  • Views 2768 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AM4379: eMMC 4-bit boot

g.f.
Guru 15520 points
Part Number: AM4379
Other Parts Discussed in Thread: CSD

Hi,

I have a question about AM437x eMMC boot.

My customer are planning to use eMMC 4bit mode boot.
In Technical Reference Manual of AM437x(spruhl7h) page.212 "5.2.6.5 MMC/SD Cards",
it said as following :
***************************************************************************
Initial 1-bit MMC Mode and optional 4-bit mode, if MMC/SD card supports it.
***************************************************************************

So, AM437x are supporting eMMC 4-bit mode boot, right?
But it said 4-bit mode is optional.
How does RBL detect 4-bit mode?
Does RBL read EXT_CSD register[183] of eMMC memory?

best regards,
g.f.

  • 0
    TI__Mastermind 44585 points
    Hello,

    We are sorry about the inconvenience but our expert on the topic is not available today and we should be able to give you feedback by early next week.

    Regards,
    Krunal
  • 0 in reply to Krunal Bhargav34
    TI__Guru 50170 points
    Hi, g.f.

    In u-boot user's guide, it says on some hardware, it may not be able to run u-boot out of ROM from the storage device. For the eMMC boot, I believe it only boots kernel from it. U-boot can detect if the eMMC is 4-bit or 1-bit.

    => mmc info
    Device: OMAP SD/MMC
    Manufacturer ID: 3
    OEM: 5344
    Name: SL08G
    Bus Speed: 48000000
    Mode : SD High Speed (50MHz)
    Rd Block Len: 512
    SD version 3.0
    High Capacity: Yes
    Capacity: 7.4 GiB
    Bus Width: 4-bit
    Erase Group Size: 512 Bytes
    =>

    Rex
  • 0 in reply to Rex Chang
    Guru 15520 points
    Hi Rex,

    Thank you for the reply.

    I want to know how the AM437x internal ROM Bootloader detects the data bus width supported
    by the eMMC memory itself.

    From AM437x TRM, I guess ROM Bootloader(RBL) will start with 1-bit mode when using
    eMMC boot mode and then if the eMMC memory are supporting 4-bit data width,
    RBL will change to 4-bit mode, is it correct?
    During 1-bit mode, I guess RBL will access to the register(CSD) of eMMC memory to find
    either eMMC memory are supporting 4-bit or not, isn't it correct?

    best regards,
    g.f.
  • 0 in reply to g.f.
    TI__Guru 50170 points
    Hi, g.f.

    eMMC standard defines the process. I found some slides on internet, cmosedu.com/.../eMMC_Architecture_and_Operation.pdf

    Please take a look at slide #36 which mentions briefly on how it works, but you should be able to find more detailed info in the eMMC standard as shown in the slide.

    Rex