marvell wifi sdio device not detected

[Dushara Jayasinghe]

Hi,

I'm trying to bring up a marvell 8787 based wifi chip on an atmel 
sama5d2 based board. The kernel version I'm on is 4.4 (specific version 
is at https://github.com/linux4sam/linux-at91/tree/linux4sam_5.5).

The wifi controller is a WYSBMVGXB from TAIYO YUDEN. The device tree 
configuration for the mmc bus I've used is as follows:

                 sdmmc1: sdio-host at b0000000 {
                         pinctrl-names = "default";
                         pinctrl-0 = <&pinctrl_sdmmc1_default>;
                         mmc-pwrseq = <&sdhci0_pwrseq>;
                         bus-width = <4>;
                         broken-cd;
                         status = "okay"; /* conflict with qspi0 */
                 };

I've used a modified pwrseq driver that drives the IO as specified in 
the controller data sheet and confirmed that the lines are controlled as 
expected during startup. I can also see some clock activity on the sdio 
bus, but doesn't seem to detect a device on the bus.

The mwifiex_sdio driver is statically compiled.

Can anyone offer any suggestions on how I can debug this issue?

Also, I don't quite understand how the mwifiex_sdio driver is attached 
to that specific bus. My understanding based on the i2c, spi buses are, 
the device tree can specify the devices hanging off these buses and the 
appropriate driver is loaded. However, the mmc/sdio dts entries dob't 
seem to be following the same pattern.

Thank you and regards,

Dushara