Get spiflash driver working

[mithro]

Be able to read the SPI flash...

• https://www.kernel.org/doc/Documentation/spi/

• Documentation/devicetree/bindings/spi/spi-bus.txt

• Documentation/devicetree/bindings/spi/spi-gpio.txt

• Documentation/devicetree/bindings/mtd/m25p80.txt

• Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt

• QEMU Emulation - Get SPI flash bit banging working qemu-litex#4

[mithro]

The following device tree was needed to get the spiflash bitbanging working;

	spiflash_bitbang_out: gpio-controller@e0005000 {
		compatible = "basic-mmio-gpio", "wd,mbl-gpio";
		reg = <0xe0005000 0x4>;
		#gpio-cells = <2>;
		gpio-controller;
		reg-names = "dat";
		big-endian;
	};
	spiflash_bitbang_in: gpio-controller@e0005004 {
		compatible = "basic-mmio-gpio", "wd,mbl-gpio";
		reg = <0xe0005004 0x4>;
		#gpio-cells = <2>;
		gpio-controller;
		reg-names = "dat";
		no-output;
		big-endian;
	};

        spi {
                compatible = "spi-gpio";
                #address-cells = <0x1>;
                ranges;

                gpio-mosi =	<&spiflash_bitbang_out 0 0>;	// 0x01 on reg0
                gpio-sck =	<&spiflash_bitbang_out 1 0>;	// 0x02 on reg0
                cs-gpios = 	<&spiflash_bitbang_out 2 0>;	// 0x03 on reg0
                gpio-miso = 	<&spiflash_bitbang_in  0 0>;	// 0x01 on reg1
                num-chipselects = <1>;

                /* clients */
		m25p16@0 {
			#address-cells = <1>;
			#size-cells = <1>;
			compatible = "spansion,m25p16", "jedec,spi-nor";
			spi-max-frequency = <40000000>;
			reg = <0>;
			//m25p,fast-read;

			// Values in the partition table should be relative to the
			// flash start address...
			partitions {
				compatible = "fixed-partitions";
				#address-cells = <1>;
				#size-cells = <1>;

				/* FPGA gateware */
				partition@0 {
					label = "gateware";
					reg = <0x0000000 0x80000>;
					read-only;
				};

				/* MiSoC / LiteX BIOS */
				partition@80000 {
					label = "bios";
					reg = <0x00080000 0x8000>;
					read-only;
				};

				/* HDMI2USB Firmware (or Linux Kernel?) */
				partition@88000 {
					label = "firmware";
					reg = <0x00088000 0x178000>;
					read-only;
				};
			};
		};
        };
	/************************************************************************/

You then get the following dmesg output;

m25p80 spi32766.0: m25p16 (2048 Kbytes)
3 ofpart partitions found on MTD device spi32766.0
Creating 3 MTD partitions on "spi32766.0":
0x000000000000-0x000000080000 : "gateware"
0x000000080000-0x000000088000 : "bios"
0x000000088000-0x000000200000 : "firmware"
spi_gpio spi: registered child spi32766.0