i have imx6q connected on usdhc1 with a murata sdio module sn8000, with his external pinout directly connected to internal bcm43362 broadcom chip. Using brcmfmac linux driver, on kernel 3.10 (and some adaption to the brcmfmac driver since this chip starts to be supported on kernel 3.14), i could have the module correctly SDIO-probed (4-bit mode) and working properly. It seems that after some changes to the drive-strength controlling processor pin config, the module started to get successfully probed.
The sequence of the init operations seems to be the following:
a. linux generic SDIO driver probe the bus
b. once chip is detected, brcmfmac driver specific probe is used
c. brcmfmac initialize the chip and upload the firmware
d. userspace setup
e. wlan0 up
Now, after some days, the module started to fail on SDIO probe (step "a", still no brcmfmac driver involved here), and then, after some additional retries, the module is no more successfully probed.
So issue is still at SDIO probing stage (linux throw SDIO error -110, timeout). I would appreciate any information useful to debug and understand why the probe fails, especially:
- any useful information on the driver strength or configuration of the pins
- any sample sn8000 devicetree
Actaully i am not setting "vqmmc", if i set it, the kernel complains that cannot set the lines voltage level (tested both 3.3 or 1.8).
I have oscilloscope available, i see SDIO clk and commands happening, but no replies or state changes in the 4 data lines.
Every help is very appreciated