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Sven Van Asbroeck
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Allow bare minimum platform device core and driver to be easily tested
Provide a forked `defconfig` and devicetree, so the platform device core and driver can be easily tested on QEMU, or a Raspberri Pi Zero. Although called "bcm2835-rng-rust", this is not a functional hwrng driver, just a bare minimum platform_device. All it will do is log a message to dmesg: [ ] rust_kernel: Rust platform_device probed and show up in sysfs: /sys/bus/platform/driver/bcm2835-rng-rust/ (the driver) /sys/bus/platform/devices/bcm2835-rng-rust/ (the device) How to run on QEMU ================== Download a Raspbian image. I used `2021-03-04-raspios-buster-armhf-lite.img`. It will consist of two partitions. Discover their offsets using: ```sh $ fdisk -l 2021-03-04-raspios-buster-armhf-lite.img Device Boot Start End Sectors Size Id Type 2021-03-04-raspios-buster-armhf-lite.img1 8192 532479 524288 256M c W95 FAT32 (LBA) 2021-03-04-raspios-buster-armhf-lite.img2 532480 3645439 3112960 1.5G 83 Linux ``` Mount the second partition on your PC: (note how the offset is multiplied by 512) ```sh $ mount -o loop,offset=$((512*532480)) 2021-03-04-raspios-buster-armhf-lite.img /mnt Comment out everything in /etc/ld.so.preload - otherwise the Raspbian rootfs cannot support a mainline kernel: $ vi /etc/ld.so.preload # comment everything out $ umount /mnt ``` Build the kernel for arm 32-bit: ```sh $ make bcm2835_rust_defconfig # defconfig forked so `bcm2835-rng-rust` binds to our driver $ make zImage dtbs modules ``` Start QEMU: ```sh # to boot mainline, make sure that /etc/ld.so.preload is commented out # in the Raspbian image. qemu-system-arm \ -M raspi2 \ -append "rw earlyprintk loglevel=8 console=ttyAMA0,115200 dwc_otg.lpm_enable=0 root=/dev/mmcblk0p2 rootwait" \ -cpu arm1176 \ -dtb bcm2836-rpi-2-b-rust.dts \ -hda ./2021-03-04-raspios-buster-armhf-lite.img \ -kernel zImage \ -m 1G \ -smp 4 \ -nographic \ ; How to run on a Raspberry Pi Zero(W) ==================================== Follow the instructions for QEMU above. Deploy the Raspbian image to SD card. Copy zImage and bcm2835-rpi-zero-w-rust.dtb to Raspbian's first (boot) partition: ``` zImage -> boot partition: kernel.img bcm2835-rpi-zero-w-rust.dtb -> boot partition: bcm2708-rpi-0-w.dtb ``` If you'd like wifi to keep working, also copy the kernel modules you built to Raspbian's second partition: ```sh $ make modules_install INSTALL_MOD_PATH=<somewhere> $ cp -rfa <somewhere> <Raspbian Partition> # should end up in /lib/modules/5.12.0-rc4+/ ``` Signed-off-by: Sven Van Asbroeck <[email protected]>
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‎arch/arm/boot/dts/Makefile

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@@ -84,13 +84,15 @@ dtb-$(CONFIG_ARCH_BCM2835) += \
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bcm2835-rpi-a-plus.dtb \
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bcm2835-rpi-cm1-io1.dtb \
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bcm2836-rpi-2-b.dtb \
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bcm2836-rpi-2-b-rust.dtb \
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bcm2837-rpi-3-a-plus.dtb \
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bcm2837-rpi-3-b.dtb \
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bcm2837-rpi-3-b-plus.dtb \
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bcm2837-rpi-cm3-io3.dtb \
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bcm2711-rpi-4-b.dtb \
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bcm2835-rpi-zero.dtb \
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bcm2835-rpi-zero-w.dtb
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bcm2835-rpi-zero-w.dtb \
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bcm2835-rpi-zero-w-rust.dtb
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dtb-$(CONFIG_ARCH_BCM_5301X) += \
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bcm4708-asus-rt-ac56u.dtb \
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bcm4708-asus-rt-ac68u.dtb \

‎arch/arm/boot/dts/bcm2835-rpi-zero-w-rust.dts

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// SPDX-License-Identifier: GPL-2.0+
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/*
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* Copyright (C) 2017 Stefan Wahren <[email protected]>
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*/
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/dts-v1/;
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#include "bcm2835.dtsi"
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#include "bcm2835-rpi.dtsi"
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#include "bcm283x-rpi-usb-otg.dtsi"
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/ {
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compatible = "raspberrypi,model-zero-w", "brcm,bcm2835";
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model = "Raspberry Pi Zero W";
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bcm2835-rng-rust {
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compatible = "brcm,bcm2835-rng";
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status = "okay";
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};
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memory@0 {
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device_type = "memory";
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reg = <0 0x20000000>;
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};
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chosen {
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/* 8250 auxiliary UART instead of pl011 */
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stdout-path = "serial1:115200n8";
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};
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leds {
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act {
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gpios = <&gpio 47 GPIO_ACTIVE_LOW>;
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};
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};
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wifi_pwrseq: wifi-pwrseq {
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compatible = "mmc-pwrseq-simple";
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reset-gpios = <&gpio 41 GPIO_ACTIVE_LOW>;
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};
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};
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&gpio {
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/*
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* This is based on the official GPU firmware DT blob.
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*
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* Legend:
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* "NC" = not connected (no rail from the SoC)
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* "FOO" = GPIO line named "FOO" on the schematic
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* "FOO_N" = GPIO line named "FOO" on schematic, active low
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*/
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gpio-line-names = "ID_SDA",
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"ID_SCL",
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"SDA1",
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"SCL1",
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"GPIO_GCLK",
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"GPIO5",
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"GPIO6",
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"SPI_CE1_N",
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"SPI_CE0_N",
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"SPI_MISO",
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"SPI_MOSI",
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"SPI_SCLK",
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"GPIO12",
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"GPIO13",
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/* Serial port */
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"TXD0",
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"RXD0",
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"GPIO16",
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"GPIO17",
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"GPIO18",
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"GPIO19",
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"GPIO20",
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"GPIO21",
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"GPIO22",
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"GPIO23",
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"GPIO24",
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"GPIO25",
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"GPIO26",
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"GPIO27",
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"SDA0",
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"SCL0",
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"NC", /* GPIO30 */
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"NC", /* GPIO31 */
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"NC", /* GPIO32 */
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"NC", /* GPIO33 */
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"NC", /* GPIO34 */
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"NC", /* GPIO35 */
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"NC", /* GPIO36 */
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"NC", /* GPIO37 */
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"NC", /* GPIO38 */
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"NC", /* GPIO39 */
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"CAM_GPIO1", /* GPIO40 */
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"WL_ON", /* GPIO41 */
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"NC", /* GPIO42 */
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"WIFI_CLK", /* GPIO43 */
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"CAM_GPIO0", /* GPIO44 */
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"BT_ON", /* GPIO45 */
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"HDMI_HPD_N",
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"STATUS_LED_N",
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/* Used by SD Card */
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"SD_CLK_R",
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"SD_CMD_R",
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"SD_DATA0_R",
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"SD_DATA1_R",
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"SD_DATA2_R",
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"SD_DATA3_R";
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pinctrl-0 = <&gpioout &alt0>;
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};
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&hdmi {
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hpd-gpios = <&gpio 46 GPIO_ACTIVE_LOW>;
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power-domains = <&power RPI_POWER_DOMAIN_HDMI>;
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status = "okay";
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};
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&sdhci {
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#address-cells = <1>;
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#size-cells = <0>;
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pinctrl-names = "default";
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pinctrl-0 = <&emmc_gpio34 &gpclk2_gpio43>;
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bus-width = <4>;
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mmc-pwrseq = <&wifi_pwrseq>;
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non-removable;
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status = "okay";
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brcmf: wifi@1 {
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reg = <1>;
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compatible = "brcm,bcm4329-fmac";
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};
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};
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&sdhost {
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pinctrl-names = "default";
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pinctrl-0 = <&sdhost_gpio48>;
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bus-width = <4>;
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status = "okay";
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};
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&uart0 {
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pinctrl-names = "default";
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pinctrl-0 = <&uart0_gpio32 &uart0_ctsrts_gpio30>;
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status = "okay";
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bluetooth {
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compatible = "brcm,bcm43438-bt";
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max-speed = <2000000>;
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shutdown-gpios = <&gpio 45 GPIO_ACTIVE_HIGH>;
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};
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};
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&uart1 {
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pinctrl-names = "default";
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pinctrl-0 = <&uart1_gpio14>;
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status = "okay";
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};

‎arch/arm/boot/dts/bcm2836-rpi-2-b-rust.dts

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// SPDX-License-Identifier: GPL-2.0
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/dts-v1/;
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#include "bcm2836.dtsi"
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#include "bcm2836-rpi.dtsi"
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#include "bcm283x-rpi-smsc9514.dtsi"
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#include "bcm283x-rpi-usb-host.dtsi"
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/ {
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compatible = "raspberrypi,2-model-b", "brcm,bcm2836";
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model = "Raspberry Pi 2 Model B";
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memory@0 {
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device_type = "memory";
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reg = <0 0x40000000>;
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};
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bcm2835-rng-rust {
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compatible = "brcm,bcm2835-rng";
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status = "okay";
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};
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leds {
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act {
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gpios = <&gpio 47 GPIO_ACTIVE_HIGH>;
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};
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pwr {
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label = "PWR";
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gpios = <&gpio 35 GPIO_ACTIVE_HIGH>;
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default-state = "keep";
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linux,default-trigger = "default-on";
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};
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};
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};
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&gpio {
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/*
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* Taken from rpi_SCH_2b_1p2_reduced.pdf and
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* the official GPU firmware DT blob.
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*
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* Legend:
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* "NC" = not connected (no rail from the SoC)
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* "FOO" = GPIO line named "FOO" on the schematic
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* "FOO_N" = GPIO line named "FOO" on schematic, active low
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*/
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gpio-line-names = "ID_SDA",
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"ID_SCL",
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"SDA1",
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"SCL1",
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"GPIO_GCLK",
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"GPIO5",
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"GPIO6",
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"SPI_CE1_N",
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"SPI_CE0_N",
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"SPI_MISO",
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"SPI_MOSI",
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"SPI_SCLK",
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"GPIO12",
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"GPIO13",
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/* Serial port */
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"TXD0",
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"RXD0",
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"GPIO16",
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"GPIO17",
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"GPIO18",
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"GPIO19",
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"GPIO20",
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"GPIO21",
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"GPIO22",
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"GPIO23",
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"GPIO24",
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"GPIO25",
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"GPIO26",
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"GPIO27",
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"SDA0",
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"SCL0",
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"", /* GPIO30 */
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"LAN_RUN",
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"CAM_GPIO1",
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"", /* GPIO33 */
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"", /* GPIO34 */
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"PWR_LOW_N",
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"", /* GPIO36 */
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"", /* GPIO37 */
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"USB_LIMIT",
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"", /* GPIO39 */
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"PWM0_OUT",
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"CAM_GPIO0",
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"SMPS_SCL",
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"SMPS_SDA",
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"ETHCLK",
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"PWM1_OUT",
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"HDMI_HPD_N",
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"STATUS_LED",
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/* Used by SD Card */
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"SD_CLK_R",
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"SD_CMD_R",
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"SD_DATA0_R",
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"SD_DATA1_R",
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"SD_DATA2_R",
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"SD_DATA3_R";
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pinctrl-0 = <&gpioout &alt0 &i2s_alt0>;
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/* I2S interface */
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i2s_alt0: i2s_alt0 {
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brcm,pins = <18 19 20 21>;
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brcm,function = <BCM2835_FSEL_ALT0>;
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};
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};
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&hdmi {
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hpd-gpios = <&gpio 46 GPIO_ACTIVE_LOW>;
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power-domains = <&power RPI_POWER_DOMAIN_HDMI>;
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status = "okay";
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};
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&pwm {
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pinctrl-names = "default";
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pinctrl-0 = <&pwm0_gpio40 &pwm1_gpio45>;
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status = "okay";
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};
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&sdhost {
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pinctrl-names = "default";
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pinctrl-0 = <&sdhost_gpio48>;
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bus-width = <4>;
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status = "okay";
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};
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&uart0 {
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pinctrl-names = "default";
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pinctrl-0 = <&uart0_gpio14>;
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status = "okay";
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};

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