Cannot detect the SD

[eishishibusawa]

Dear Sir

Sometimes it does not recognize the SD on the customer board.

Customer uses the i.MX6SX and Linux Version： 4.1.15-2.0.

The log is the follows.

sdhci: Tuning procedure failed, falling back to fixed sampling clock
mmc2: tuning execution failed
Waiting for removable media...
mmc2: error -5 whilst initialising SD card

Is there a similar problem?

Best Regards,

Eishi SHIBUSAWA

[igorpadykov]

Hi Eishi

one can recheck sd signals layout with sect.3.6.8 High speed signal routing recommendations

i.MX6 System Development User’s Guide :

For SD module interfaces:
– Match data and CMD trace lengths (length delta depends on bus rates)
– CLK should be longer than the longest signal in the Data/CMD group (+5 mils)
— Similar DDR rules must be followed for data, address and control as for SD module interfaces.

https://www.nxp.com/docs/en/user-guide/IMX6DQ6SDLHDG.pdf

also for reducing noise one can try to tweak drive strength of sd signals using IOMUXC_SW_PAD_CTL_PAD register

Best regards
igor
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