linux-kernel - Re: [PATCH v5 2/2] spi: Add generic SPI multiplexer

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Date:   Fri, 13 Nov 2020 16:46:33 +0100
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     chris.packham@...iedtelesis.co.nz, linux-kernel@...r.kernel.org
Cc:     andy.shevchenko@...il.com, broonie@...nel.org,
        devicetree@...r.kernel.org, linux-spi@...r.kernel.org,
        mark.rutland@....com, robh+dt@...nel.org
Subject: Re: [PATCH v5 2/2] spi: Add generic SPI multiplexer

Upon registering spi-mux's devices through spi_add_device() the kernel gets
stuck waiting for the 'spi_add_lock' mutex to be released. The mutex happens to
be held by spi-mux's parent SPI bus, which unluckily, is waiting for spi-mux's
probe to finish before releasing it.

I might aswell be doing something wrong. But so far I trust my DT
implementation:

	&spi {
		status = "okay";
		pinctrl-names = "default";
		pinctrl-0 = <&spi0_gpio7>;

		spi@0 {
			compatible = "spi-mux";
			reg = <0>;
			#address-cells = <1>;
			#size-cells = <0>;
			spi-max-frequency = <100000000>;

			mux-controls = <&gpio_mux>;

			w5500@0 {
				compatible = "wiznet,w5500";
				reg = <0>;
				pinctrl-names = "default";
				pinctrl-0 = <&eth1_pins>;
				interrupt-parent = <&gpio>;
				interrupts = <27 IRQ_TYPE_EDGE_FALLING>;
				spi-max-frequency = <30000000>;
			};

			spi-flash@1 {
				compatible = "jedec,spi-nor";
				reg = <1>;
				#address-cells = <1>;
				#size-cells = <0>;
				spi-max-frequency = <16000000>;
			};
		};
	};

Regards,
Nicolas