MMC standard tuning procedure does not work

thomaspham — Wed, 08 Sep 2021 10:10:28 GMT

Hello guys,

I'm debugging standard tuning procedure for MMC card on S32G. After switching the card to HS200 mode, I followed the steps described in the S32G manual as below:

I observed these:

The MIX_CTRL[EXE_TUNE] bit never get set to 1, it remains 0 the whole time, which is strange.
The data (tuning pattern) is received on the USDHC side, and pattern is correct.
The AUTOCMD12_ERR_STATUS[SMP_CLK_SEL] stays 0 after all, which indicates tuning failed according to the manual.

I'd like to ask if anyone face this problem before, or if you have success with tuning procedure on S32G, please drop me a hint.

Thanks and Best Regards,

Thomas

Re: MMC standard tuning procedure does not work

ttz766 — Sun, 07 Nov 2021 17:39:45 GMT

What you were attempting was the sequence in Rev 3 of the RM, which has been updated in Rev 4.

Rev 4 has still to be formally released but the new sequence is :

By default, lower frequency operation, a fixed sampling clock is used to receive signals on CMD and DAT[3:0]. Before using the

HS200, HS400, SDR104, or SDR50 modes, the Host Driver executes the tuning procedure at the mode switch sequence.

Issue uSDHC SW reset, set SYS_CTRL[RSTT] to 1.
Set VEND_SPEC[FRC_SDCLK_ON] to 1.
Set TUNING_CTRL[DIS_CMD_CHK_FOR_STD_TUNING] to 1.
Set AUTOCMD12_ERR_STATUS[EXECUTE_TUNING] to 0.
Read AUTOCMD12_ERR_STATUS[EXECUTE_TUNING] to get 0, and then write 1 to clean INT_STATUS[BRR].
Start the tuning procedure by setting TUNING_CTRL[STD_TUNING_EN] and

AUTOCMD12_ERR_STATUS[EXECUTE_TUNING] to 1.

Issue CMD19(SD)/ CMD21(eMMC) with the proper Command Transfer Type (CMD_XFR_TYP) and Auto CMD12 Error

Status (AUTOCMD12_ERR_STATUS) settings.

Wait for uSDHC BRR (Buffer Read Ready) interrupt signal is 1.
Check AUTOCMD12_ERR_STATUS[EXECUTE_TUNING]. If AUTOCMD12_ERR_STATUS[EXECUTE_TUNING] = 1,

repeat 5~6. If AUTOCMD12_ERR_STATUS[EXECUTE_TUNING] = 0, standard tuning has completed, or the tuning

has not completed within 40 attempts. The Host Driver might abort this loop if the number of loops exceeds 40 or 150ms

timeout occurs. In this case, a fixed sampling clock should be used, (AUTOCMD12_ERR_STATUS[SMP_CLK_SEL] =

0).

Sampling Clock Select, AUTOCMD12_ERR_STATUS[SMP_CLK_SEL] , is valid after

AUTOCMD12_ERR_STATUS[EXECUTE_TUNING] has changed from 1 to 0.

AUTOCMD12_ERR_STATUS[SMP_CLK_SEL] = 1, indicates tuning procedure passed.

AUTOCMD12_ERR_STATUS[SMP_CLK_SEL] = 0, indicates tuning procedure failed. The tuning result is applied to the

delay chain, CLK Tuning Control and Status (CLK_TUNE_CTRL_STATUS) [30:16], upon successful tuning procedure

completion.

Clear VEND_SPEC[FRC_SDCLK_ON].
Set MIX_CTRL[AUTO_TUNE_EN] to 1.

Can you try this out

Re: MMC standard tuning procedure does not work

thomaspham — Tue, 09 Nov 2021 07:10:03 GMT

Hi ttz766,

I have tried your sequence, and it works.

Thanks for your support!

topic Re: MMC standard tuning procedure does not work in S32G

MMC standard tuning procedure does not work

Re: MMC standard tuning procedure does not work

Re: MMC standard tuning procedure does not work