[PATCH] ARM: dts: ixp4xx: Add a devicetree for Freecom FSG-3

[Linus Walleij]

On Sun, Aug 1, 2021 at 8:59 PM Marc Zyngier <maz at kernel.org> wrote:
> Andrew Lunn <andrew at lunn.ch> wrote:

> > The driver exports the file "registers" in /sysfs. Do you see any sort
> > of application/driver running in userspace which might be talking to
> > the switch?
>
> Hmmm. Which driver? I don't see any switch-related driver, nor any
> userspace (what I have is an extremely minimal OpenWRT userspace that
> has hardly more than busybox).

I think Andrew is referring to CONFIG_MICREL_KS8995MA
drivers/net/phy/spi_ks8995.c (previously a Kendin product).
http://ww1.microchip.com/downloads/en/DeviceDoc/ks8995ma.pdf

We are guessing the FSG-3 has this switch.

Unfortunately we don't know which pins it is connected to,
but it is an SPI device. Should look like this:

+       spi {
+               compatible = "spi-gpio";
+               #address-cells = <1>;
+               #size-cells = <0>;
+
+               sck-gpios = <&gpio0 7 GPIO_ACTIVE_HIGH>;
+               miso-gpios = <&gpio0 12 GPIO_ACTIVE_HIGH>;
+               mosi-gpios = <&gpio0 6 GPIO_ACTIVE_HIGH>;
+               cs-gpios = <&gpio0 5 GPIO_ACTIVE_LOW>;
+               num-chipselects = <1>;
+
+               switch at 0 {
+                       compatible = "micrel,ks8995";
+                       reg = <0>;
+                       spi-max-frequency = <50000000>;
+               };
+       };

Maybe you can see which pins it is using in the original firmware?

It may be completely unconnected as it can also be configured from
a companion EEPROM with no interaction from the host.

Yours,
Linus Walleij