topic Re: i.mx6ulz Default SD pins for eFuse Boot in i.MX Processors

i.mx6ulz Default SD pins for eFuse Boot

Angshu — Thu, 25 Mar 2021 18:32:54 GMT

Hi,

I posted this previously and it was confirmed from nxp that for eFuses to work, we must have the default SD2 pins assigned to the SD slot to boot from SD 2 with eFuses. : https://community.nxp.com/t5/i-MX-Processors/I-MX6ULZ-eFuse-boot-from-SD-with-custom-pinmux-for-SD-slot/m-p/1238954

However, now we are attempting to make the changes on our board and are having a difficult time understanding which actually the default SD2 slot pins are.

So as an example lets take SD2_CLK signal. Based on the RM the USDHC2 CLK can be routed to SD2_CLK, GPIO3_IO24, and NAND_RE_B pins/pads. But ALT1 mode is for only SD2_CLK and NAND_RE_B. We used SD2_CLK as this seems like the default SD2 clock pin. However, on the 6ull EVK they are actually using the NAND_RE_B for SD2_CLK and similarly the rest of the SD2 signals are also different and related to NAND instead of SD2 (e.g NAND_WE_B instead of SD2_CMD).

We blew the eFuses and the fuse values were read correct afterwards but could not boot to u-boot or OS. We can boot the OS fine via Serial downloader mode so all other operations are verified to work. Fuse values set and read below.

fuse prog 0 6 0x10

fuse prog 0 5 0x2840

So, ultimately our question is, which are the default pins for the SD2 signals that the ROM code looks in order to boot? the SD2_XXX or NAND_XXXX? If it is NAND_XXX, why is it that one? Or does it look at both?

The reference manual table :

And our schematics for SD2 slot is as follows:

Reference design Schematic snippet from the EVK schematic file.

Re: i.mx6ulz Default SD pins for eFuse Boot

igorpadykov — Fri, 26 Mar 2021 00:30:24 GMT

Hi Angshu

default SD pins for boot are described in sect.8.5.3.4 IOMUX configuration for SD/MMC

i.MX 6ULZ Applications Processor Reference Manual

Best regards
igor

Re: i.mx6ulz Default SD pins for eFuse Boot

Angshu — Fri, 26 Mar 2021 00:40:12 GMT

Hi Igor,

Thank you for the answer. We just ran into that table after posting here. Much appreciated.

Re: i.mx6ulz Default SD pins for eFuse Boot

Angshu — Wed, 31 Mar 2021 17:59:55 GMT

Hi Igor,

Follow up question regarding this. Currently we have CLK, CMD, Data00 - 03 lines connected for SD.

We are rerouting it now as follows :

Signal Pin Pad
USDCH2_CLK NAND_RE_B D8
USDCH2_CMD NAND_WE_B C8
USDCH2_DATA0 NAND_DATA00 D7
USDCH2_DATA1 NAND_DATA01 B7
USDCH2_DATA2 NAND_DATA02 A7
USDCH2_DATA3 NAND_DATA03 D6

Will this be enough for the ROM to boot from our SD2 slot or do we need to connect other sd2 related signals that we do not use at the moment such as these below?

DATA4 NAND_DATA04
DATA5 NAND_DATA05
DATA6 NAND_DATA06
DATA7 NAND_DATA07
VSELECT GPIO1_IO08
RESET_B NAND_ALE

Re: i.mx6ulz Default SD pins for eFuse Boot

igorpadykov — Thu, 01 Apr 2021 05:14:48 GMT

yes this is enough for ROM to boot from SD2.

Best regards
igor