How to use designware SPI for SPI loopback test on em_starterkit

[SiyuanCheng-CN]

Problem:
I'm trying to run em_starterkit with designware SPI driver on SPI loopback test, found error:

START - test_spi_loopback                                                                                                                                                          
I: SPI test on buffers TX/RX 0x800013d0/0x80000044                                                                                                                                 
                                                                                                                                                                                   
    Assertion failed at WEST_TOPDIR/zephyr/tests/drivers/spi/spi_loopback/src/spi.c:546: spi_loopback_test_spi_loopback: (spi_is_ready(&spi_slow) is false)                        
Slow spi lookback device is not ready                                                                                                                                                  

What I do:
Added cs-gpios = <&creg_gpio 0 GPIO_ACTIVE_HIGH>; in em_starterkit.overlay. CS gpio port ready validation is solved, but still found device_is_ready(spec->bus) returns false in spi_is_ready().
Now SPI dts:

		spi0: spi@f0006000 {
			compatible = "snps,designware-spi";
			reg = < 0xf0006000 0x1000 >;
			clocks = < &sysclk >;
			interrupt-parent = < &intc >;
			#address-cells = < 0x1 >;
			#size-cells = < 0x0 >;
			interrupts = < 0x1b 0x1 >;
			cs-gpios = < &creg_gpio 0x0 0x0 >;
			status = "okay";
			slow@0 {
				compatible = "test-spi-loopback-slow";
				reg = < 0x0 >;
				spi-max-frequency = < 0x1f400 >;
			};
			fast@0 {
				compatible = "test-spi-loopback-fast";
				reg = < 0x0 >;
				spi-max-frequency = < 0xf42400 >;
			};
		};
		spi1: spi@f0007000 {
			compatible = "snps,designware-spi";
			reg = < 0xf0007000 0x1000 >;
			clocks = < &sysclk >;
			interrupt-parent = < &intc >;
			#address-cells = < 0x1 >;
			#size-cells = < 0x0 >;
			interrupts = < 0x1c 0x1 >;
			status = "okay";
		};
		creg_gpio: creg_gpio@f0000014 {
			compatible = "snps,creg-gpio";
			reg = < 0xf0000014 0x4 >;
			ngpios = < 0x6 >;
			bit_per_gpio = < 0x1 >;
			off_val = < 0x0 >;
			on_val = < 0x1 >;
			gpio-controller;
			#gpio-cells = < 0x2 >;
			status = "okay";
			phandle = < 0x3 >;
		};

What is missing or is designware SPI driver is incompatible with current API macro?

[evgeniy-paltsev]

Hi @SiyuanCheng-CN ,

I'm wondering what Zephyr version are you using? Do you know if this thing was working before for DW SPI?

[SiyuanCheng-CN]

rebased to latest main branch, zephyr-v3.2.0-2256-g7ef519726036.
I see status = "okay" in board spi dts file then I assume emsk should work for DW SPI. And I saw em_starterkit.overlay in spi_loopback test. But I guess no one tested before whether it works. Not sure about if emsk can work with DW SPI before, but given the em_starterkit.yaml, it should work.