• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 98 subscribers
  • Views 347 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.

MMC clock reference setting for AM3874

Poh Boon Teo
Intellectual 710 points

Hi,

On the mmc_host_def.h file, there is a setting for the MMC clock reference as shown below:

/* Clock Configurations and Macros */
#if defined(CONFIG_TI816X)
#define MMC_CLOCK_REFERENCE             48
#elif defined(CONFIG_TI814X)
#define MMC_CLOCK_REFERENCE             192
#endif

For TI814X definition, I have tested the EVM board by setting it to 48 but the SD card is not able to boot up.

One question I have is whether can the MMC_CLOCK_REFERENCE goes below 192?

If it can, what are the options I have?

Thanks and regards,

pb

  • 0
    TI__Guru**** 170625 points

    Hi Poh,

    MMC 192 MHz functional clock is the default and max clock frequency. You can try to decrease the 192 value but I am not sure if this will work, this is not tested. Also I can not find min value for the MMC functional clock.

    This is what we have in DM814x TRM:

    18.1.2 Features
    The main features of the MMC/SD/SDIO host controller are:
    – 192 MHz functional clock source input

    Note also that 192 MHz is the default ROM code settings:

    4.4.3 Clocking Configuration
    Table 4-7. ROM Code Default Clock Settings

    SYSCLK8 = 192MHz (PLL_USB/5)/1

    Check also the below thread, might be in help:

    http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/235022.aspx

    Regards,
    Pavel