imx6ulevk can't set low speed for SDIO

[ida_jiang]

Hi,

   I'm trying to debug a wifi/bt module for imx6ulevk. The hardware connection is SDIO with nothing. I could compile the module for L4.9.88_2.0.0_ga. When I used imx6ul-14x14-evk-btwifi-oob.btwifi to boot the board, the log showed as follow:

   Compared to the normal wifi/bt module, this mmc0 was at address 8800. was that wrong? The module couldn't work. And when I knowed the module's max working speed is 50mhz, I changed the dts:

        &usdhc1 {

             MX6UL_PAD_SD1_CMD__USDHC1_CMD      0x17059     ----->  0x17019
             MX6UL_PAD_SD1_CLK__USDHC1_CLK      0x10071        ----->  0x10039

             ...};

   Then boot log showed that the board didn't recongnize SDIO device. 

   A new SDIO device address should be 0001, right?

   The dts changes showed above had something wrong ?

   Thanks!

[igorpadykov]

Hi lda

reason that device was not recognized may be signal integrity issues,

one can try different settings for MX6UL_PAD_SD1_CMD__USDHC1_CMD/CLK:

they are described in sect.30.5.270 SW_PAD_CTL_PAD_SD1_CMD SW PAD Control
Register (IOMUXC_SW_PAD_CTL_PAD_SD1_CMD)

i.MX 6UltraLite Applications Processor Reference Manual

Recheck board sdio layout using sect.3.5.2 High speed signal routing recommendations

Hardware Development Guide for the i.MX 6UltraLite Applications Processor

Best regards
igor
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