No result with poll_once on dtoverlay sdio-1bit

[dalmago]

I connected a secondary SD card on my Raspberry Pi 3 B using the SDIO pins in "1 bit mode", but the system only finds the card when its already inserted on boot.

My config.txt has the following:
dtoverlay=sdio-1bit,poll_once=off

I also tried removing the non-removable; line from the dts file and tried compiling it again, but nothing changed.

[dalmago]

I also tried using poll_once=no and adding broken-cd on the dts file.

[pelwell]

This is an unfortunate problem with boolean Device Tree properties and overlays. Boolean properties are defined to be TRUE if the property is present, and FALSE if it isn't - the actual value assigned to the property is irrelevant. Overlays and add properties and modify them, but they can't delete them - it is a fundamental limitation of the overlay representation.

The MMC block on a Pi3 is used to control the WiFi interface via SDIO. We were advised by Broadcom to disable usual card status polling on the interface, hence the presence of the non-removable property in the base DTBs of the Pi 3 and the Pi Zero W.

There is an ugly workaround - it should be possible to modify the sdio overlays to disable the existing node (rather than patching it) and create a new one alongside it that only contains non-removable if poll_once is true. I'll post a DTBO here for testing.

[pelwell]

Can you test this .dtbo for me? Download it somewhere, then:

cp /boot/overlays/sdio-1bit.dtbo sdio-1bit.dtbo.bak
sudo cp sdio-1bit.dtbo /boot/overlays

and reboot.

[dalmago]

It worked great, thanks!

Can you post the dts file as well?

[pelwell]

Here you go: https://github.com/raspberrypi/linux/blob/rpi-4.14.y/arch/arm/boot/dts/overlays/sdio-1bit-overlay.dts
It's in the rpi-4.14-y branch now, so it will be in future firmware+kernel releases.