i.MX6 sometimes fails to generate SD3_CLK to read the eMMC boot partition

[oway]

A single sample of our i.MX6Q custom boards has an intermittent boot up issue: 

When pressing the i.MX6 reset button (or on POR), the i.MX6 sometimes (~20%) fails to generate SD3_CLK to read the boot partition of the eMMC (on SD3).  In this situation, the i.MX6 enters serial download mode instead of booting from the eMMC.

Once in the serial download mode, I have verified the DDR3 SDRAM passes cal and stress test.

The 32kHz and 24MHz clocks look good.

For debug, I have forced the i.MX6 to use its internal ring oscillator, instead of the external 32kHz crystal ... and booting is still intermittent.

Ideas?

[igorpadykov]

Hi oway

is it booting fine from cold boot (all board is unpowered) or

with powered board with reset (POR) only processor (other board components

are still powered) ? There may be issues with reset if there is no PMIC reset

(which resets all board power supplies).

Best regards
igor
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

[oway]

Igor,

Both … The failure to boot from eMMC happens (~20%) booting from cold boot (all board is unpowered) and with powered board with reset (POR) only processor (other board components are still powered).

[igorpadykov]

Hi oway

could you try to extend POR up to 1 sec.

Is it booting fine from other media, sd card for example.

~igor

[oway]

Igor,

On this unit, I have already burned the fuses for booting from eMMC on SD3. So I cannot choose other boot media.

To extend POR 1 sec, do I simply hold the i.MX6 reset button for 1 sec?

Also, since the eMMC is already powered when I press the i.MX6 reset button, would extending POR make any difference?

Thanks

[igorpadykov]

one can ground POR, then turn on board, release POR after several seconds.

After "i.MX6 sometimes (~20%) fails to generate SD3_CLK " - please attach jtag and check

SRC_SBMR1,2, do they have correct boot settings.

Best regards
igor

[oway]

Igor,

Since I do not have a JTAG analyzer, what is a low cost one you would recommend for this?

Thanks

[igorpadykov]

Hi oway

many people use j-link, in general any debugger supporting cortex-a9

may be used.

Best regards
igor

[oway]

Igor,

If there is JTAG software required to check SRC_SBMR1,2 when using the j-link hardware, … can you please suggest what low-cost JTAG software is needed?

Thanks