Getting two chip select pins working with /dev/spi0 on the Coral Dev Board Mini

[asymingt]

Description

I'm having a crazy hard time getting two SPI devices to work with the spidev driver in mendel on the Google Coral Dev Board Mini. I modified the device tree in the following way to get two adjacent pins (GPIO5 and GPIO8) functioning as chip selects for two devices on the same bus.

diff --git a/arch/arm64/boot/dts/mediatek/mt8167-coral.dts b/arch/arm64/boot/dts/mediatek/mt8167-coral.dts
index c08bb12162fc..2550f2cfb9d7 100644
--- a/arch/arm64/boot/dts/mediatek/mt8167-coral.dts
+++ b/arch/arm64/boot/dts/mediatek/mt8167-coral.dts
@@ -301,8 +301,9 @@
                pins1 {
                        pinmux = <MT8167_PIN_3_EINT3__FUNC_SPI_MI>,
                                 <MT8167_PIN_4_EINT4__FUNC_SPI_MO>,
-                                <MT8167_PIN_5_EINT5__FUNC_SPI_CSB>,
-                                <MT8167_PIN_6_EINT6__FUNC_SPI_CLK>;
+                                <MT8167_PIN_6_EINT6__FUNC_SPI_CLK>,
+                                <MT8167_PIN_5_EINT5__FUNC_GPIO5>,
+                                <MT8167_PIN_8_EINT8__FUNC_GPIO8>;
                        bias-disable;
                };
        };
@@ -647,6 +648,8 @@
        status = "okay";
        pinctrl-names = "default";
        pinctrl-0 = <&spi_pins>;
+       cs-gpios = <&pio 5 GPIO_ACTIVE_HIGH>,
+                  <&pio 8 GPIO_ACTIVE_HIGH>;
        spidev@0 {
                #address-cells = <1>;
                #size-cells = <1>;
@@ -654,6 +657,13 @@
                spi-max-frequency = <2000000>;
                reg = <0>;
        };
+       spidev@1 {
+               #address-cells = <1>;
+               #size-cells = <1>;
+               compatible = "rohm,dh2228fv";
+               spi-max-frequency = <400000>;
+               reg = <1>;
+       };
 };
 
 &pwm {

The system boots and I see /dev/spi0.0 and /dev/spi0.1 enumerated, but communication fails. It's unlikely to be an electrical issue because I'm using a production board (PXFMINI) that has previously worked with a raspberry pi zero. Is there any chance that the SPI chip itself is not respecting the pinmux and using CSB despite my request not to?

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Issue Type

Performance

Operating System

Mendel Linux

Coral Device

Dev Board Mini

Other Devices

No response

Programming Language

Other

Relevant Log Output

No response