# Tutorial 06 - Drivers: GPIO and UART
## tl;dr
Now that we enabled safe globals in the previous tutorial, the infrastructure is
laid for adding the first real device drivers. We throw out the magic QEMU
console and use a real UART now. Like serious embedded hackers do!
- For the first time, we will be able to run the code on the real hardware.
- Therefore, building is now differentiated between the **RPi 3** and the **RPi4**.
- By default, all `Makefile` targets will build for the **RPi 3**.
- In order to build for the the **RPi4**, prepend `BSP=rpi4` to each target. For example:
- `BSP=rpi4 make`
- `BSP=rpi4 make doc`
- Unfortunately, QEMU does not yet support the **RPi4**, so `BSP=rpi4 make qemu` won't work.
- A `DeviceDriver` trait is added for abstracting `BSP` driver implementations
from kernel code.
- Drivers are stored in `bsp/driver`, and can be reused between `BSP`s.
- Introducing the `GPIO` driver, which pinmuxes the RPi's PL011 UART.
- Most importantly, the `PL011Uart` driver: It implements the `Console`
traits and is from now on used as the system console output.
- `BSP`s now contain a`memory_map.rs`. In the specific case, they contain the
RPi's MMIO addresses which are used to instantiate compatible device drivers
from `bsp/driver`.
- We also modify the `panic!` handler, so that it does not anymore rely on `println!`, which uses
the globally-shared instance of the `UART` that might be locked when an error is encountered (for
now this can't happen due to the `NullLock`, but with a real lock it becomes an issue).
- Instead, it creates a new UART driver instance, re-initializes the device and uses that one to
print. This increases the chances that the system is able to print a final important message
before it suspends itself.
## Boot it from SD card
Some steps for preparing the SD card differ between RPi3 and RPi4, so be careful.
### Common for both
1. Make a single `FAT32` partition named `boot`.
2. On the card, generate a file named `config.txt` with the following contents:
```txt
init_uart_clock=48000000
```
### Pi 3
3. Copy the following files from the [Raspberry Pi firmware repo](https://github.com/raspberrypi/firmware/tree/master/boot) onto the SD card:
- [bootcode.bin](https://github.com/raspberrypi/firmware/raw/master/boot/bootcode.bin)
- [fixup.dat](https://github.com/raspberrypi/firmware/raw/master/boot/fixup.dat)
- [start.elf](https://github.com/raspberrypi/firmware/raw/master/boot/start.elf)
4. Run `make` and copy the [kernel8.img](kernel8.img) onto the SD card.
### Pi 4
3. Copy the following files from the [Raspberry Pi firmware repo](https://github.com/raspberrypi/firmware/tree/master/boot) onto the SD card:
- [fixup4.dat](https://github.com/raspberrypi/firmware/raw/master/boot/fixup4.dat)
- [start4.elf](https://github.com/raspberrypi/firmware/raw/master/boot/start.elf)
- [bcm2711-rpi-4-b.dtb](https://github.com/raspberrypi/firmware/raw/master/boot/bcm2711-rpi-4-b.dtb)
4. Run `BSP=rpi4 make` and copy the [kernel8.img](kernel8.img) onto the SD card.
### Common again
5. Insert the SD card into the RPi and connect the USB serial to your host PC.
- Wiring diagram at [top-level README](../README.md#usb-serial).
6. Run `screen` (you might need to install it first):
```console
sudo screen /dev/ttyUSB0 115200
```
7. Hit Enter to kick off the kernel boot process. Observe the output:
```console
[0] Booting on: Raspberry Pi 3
[1] Drivers loaded:
1. GPIO
2. PL011Uart
[2] Chars written: 84
[3] Echoing input now
```
8. Exit screen by pressing ctrl-a ctrl-d or disconnecting the USB serial.
## Diff to previous
```diff
diff -uNr 05_safe_globals/Cargo.toml 06_drivers_gpio_uart/Cargo.toml
--- 05_safe_globals/Cargo.toml
+++ 06_drivers_gpio_uart/Cargo.toml
@@ -10,11 +10,12 @@
# The features section is used to select the target board.
[features]
default = []
-bsp_rpi3 = ["cortex-a"]
-bsp_rpi4 = ["cortex-a"]
+bsp_rpi3 = ["cortex-a", "register"]
+bsp_rpi4 = ["cortex-a", "register"]
[dependencies]
r0 = "0.2.*"
# Optional dependencies
cortex-a = { version = "2.8.x", optional = true }
+register = { version = "0.4.x", optional = true }
diff -uNr 05_safe_globals/src/arch/aarch64.rs 06_drivers_gpio_uart/src/arch/aarch64.rs
--- 05_safe_globals/src/arch/aarch64.rs
+++ 06_drivers_gpio_uart/src/arch/aarch64.rs
@@ -33,6 +33,15 @@
// Implementation of the kernel's architecture abstraction code
//--------------------------------------------------------------------------------------------------
+pub use asm::nop;
+
+/// Spin for `n` cycles.
+pub fn spin_for_cycles(n: usize) {
+ for _ in 0..n {
+ asm::nop();
+ }
+}
+
/// Pause execution on the calling CPU core.
#[inline(always)]
pub fn wait_forever() -> ! {
diff -uNr 05_safe_globals/src/bsp/driver/bcm/bcm2xxx_gpio.rs 06_drivers_gpio_uart/src/bsp/driver/bcm/bcm2xxx_gpio.rs
--- 05_safe_globals/src/bsp/driver/bcm/bcm2xxx_gpio.rs
+++ 06_drivers_gpio_uart/src/bsp/driver/bcm/bcm2xxx_gpio.rs
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+//
+// Copyright (c) 2018-2019 Andre Richter
+
+//! GPIO driver.
+
+use crate::{arch, arch::sync::NullLock, interface};
+use core::ops;
+use register::{mmio::ReadWrite, register_bitfields, register_structs};
+
+// GPIO registers.
+//
+// Descriptions taken from
+// https://github.com/raspberrypi/documentation/files/1888662/BCM2837-ARM-Peripherals.-.Revised.-.V2-1.pdf
+register_bitfields! {
+ u32,
+
+ /// GPIO Function Select 1
+ GPFSEL1 [
+ /// Pin 15
+ FSEL15 OFFSET(15) NUMBITS(3) [
+ Input = 0b000,
+ Output = 0b001,
+ AltFunc0 = 0b100 // PL011 UART RX
+
+ ],
+
+ /// Pin 14
+ FSEL14 OFFSET(12) NUMBITS(3) [
+ Input = 0b000,
+ Output = 0b001,
+ AltFunc0 = 0b100 // PL011 UART TX
+ ]
+ ],
+
+ /// GPIO Pull-up/down Clock Register 0
+ GPPUDCLK0 [
+ /// Pin 15
+ PUDCLK15 OFFSET(15) NUMBITS(1) [
+ NoEffect = 0,
+ AssertClock = 1
+ ],
+
+ /// Pin 14
+ PUDCLK14 OFFSET(14) NUMBITS(1) [
+ NoEffect = 0,
+ AssertClock = 1
+ ]
+ ]
+}
+
+register_structs! {
+ #[allow(non_snake_case)]
+ RegisterBlock {
+ (0x00 => GPFSEL0: ReadWrite),
+ (0x04 => GPFSEL1: ReadWrite),
+ (0x08 => GPFSEL2: ReadWrite),
+ (0x0C => GPFSEL3: ReadWrite),
+ (0x10 => GPFSEL4: ReadWrite),
+ (0x14 => GPFSEL5: ReadWrite),
+ (0x18 => _reserved1),
+ (0x94 => GPPUD: ReadWrite),
+ (0x98 => GPPUDCLK0: ReadWrite),
+ (0x9C => GPPUDCLK1: ReadWrite),
+ (0xA0 => @END),
+ }
+}
+
+/// The driver's private data.
+struct GPIOInner {
+ base_addr: usize,
+}
+
+/// Deref to RegisterBlock.
+impl ops::Deref for GPIOInner {
+ type Target = RegisterBlock;
+
+ fn deref(&self) -> &Self::Target {
+ unsafe { &*self.ptr() }
+ }
+}
+
+impl GPIOInner {
+ const fn new(base_addr: usize) -> GPIOInner {
+ GPIOInner { base_addr }
+ }
+
+ /// Return a pointer to the register block.
+ fn ptr(&self) -> *const RegisterBlock {
+ self.base_addr as *const _
+ }
+}
+
+//--------------------------------------------------------------------------------------------------
+// BSP-public
+//--------------------------------------------------------------------------------------------------
+use interface::sync::Mutex;
+
+/// The driver's main struct.
+pub struct GPIO {
+ inner: NullLock,
+}
+
+impl GPIO {
+ pub const unsafe fn new(base_addr: usize) -> GPIO {
+ GPIO {
+ inner: NullLock::new(GPIOInner::new(base_addr)),
+ }
+ }
+
+ /// Map PL011 UART as standard output.
+ ///
+ /// TX to pin 14
+ /// RX to pin 15
+ pub fn map_pl011_uart(&self) {
+ let mut r = &self.inner;
+ r.lock(|inner| {
+ // Map to pins.
+ inner
+ .GPFSEL1
+ .modify(GPFSEL1::FSEL14::AltFunc0 + GPFSEL1::FSEL15::AltFunc0);
+
+ // Enable pins 14 and 15.
+ inner.GPPUD.set(0);
+ arch::spin_for_cycles(150);
+
+ inner
+ .GPPUDCLK0
+ .write(GPPUDCLK0::PUDCLK14::AssertClock + GPPUDCLK0::PUDCLK15::AssertClock);
+ arch::spin_for_cycles(150);
+
+ inner.GPPUDCLK0.set(0);
+ })
+ }
+}
+
+//--------------------------------------------------------------------------------------------------
+// OS interface implementations
+//--------------------------------------------------------------------------------------------------
+
+impl interface::driver::DeviceDriver for GPIO {
+ fn compatible(&self) -> &str {
+ "GPIO"
+ }
+}
diff -uNr 05_safe_globals/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs 06_drivers_gpio_uart/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs
--- 05_safe_globals/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs
+++ 06_drivers_gpio_uart/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs
@@ -0,0 +1,307 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+//
+// Copyright (c) 2018-2019 Andre Richter
+
+//! PL011 UART driver.
+
+use crate::{arch, arch::sync::NullLock, interface};
+use core::{fmt, ops};
+use register::{mmio::*, register_bitfields, register_structs};
+
+// PL011 UART registers.
+//
+// Descriptions taken from
+// https://github.com/raspberrypi/documentation/files/1888662/BCM2837-ARM-Peripherals.-.Revised.-.V2-1.pdf
+register_bitfields! {
+ u32,
+
+ /// Flag Register
+ FR [
+ /// Transmit FIFO empty. The meaning of this bit depends on the state of the FEN bit in the
+ /// Line Control Register, UARTLCR_ LCRH.
+ ///
+ /// If the FIFO is disabled, this bit is set when the transmit holding register is empty. If
+ /// the FIFO is enabled, the TXFE bit is set when the transmit FIFO is empty. This bit does
+ /// not indicate if there is data in the transmit shift register.
+ TXFE OFFSET(7) NUMBITS(1) [],
+
+ /// Transmit FIFO full. The meaning of this bit depends on the state of the FEN bit in the
+ /// UARTLCR_ LCRH Register.
+ ///
+ /// If the FIFO is disabled, this bit is set when the transmit holding register is full. If
+ /// the FIFO is enabled, the TXFF bit is set when the transmit FIFO is full.
+ TXFF OFFSET(5) NUMBITS(1) [],
+
+ /// Receive FIFO empty. The meaning of this bit depends on the state of the FEN bit in the
+ /// UARTLCR_H Register.
+ ///
+ /// If the FIFO is disabled, this bit is set when the receive holding register is empty. If
+ /// the FIFO is enabled, the RXFE bit is set when the receive FIFO is empty.
+ RXFE OFFSET(4) NUMBITS(1) []
+ ],
+
+ /// Integer Baud rate divisor
+ IBRD [
+ /// Integer Baud rate divisor
+ IBRD OFFSET(0) NUMBITS(16) []
+ ],
+
+ /// Fractional Baud rate divisor
+ FBRD [
+ /// Fractional Baud rate divisor
+ FBRD OFFSET(0) NUMBITS(6) []
+ ],
+
+ /// Line Control register
+ LCRH [
+ /// Word length. These bits indicate the number of data bits transmitted or received in a
+ /// frame.
+ WLEN OFFSET(5) NUMBITS(2) [
+ FiveBit = 0b00,
+ SixBit = 0b01,
+ SevenBit = 0b10,
+ EightBit = 0b11
+ ],
+
+ /// Enable FIFOs:
+ ///
+ /// 0 = FIFOs are disabled (character mode) that is, the FIFOs become 1-byte-deep holding
+ /// registers
+ ///
+ /// 1 = transmit and receive FIFO buffers are enabled (FIFO mode).
+ FEN OFFSET(4) NUMBITS(1) [
+ FifosDisabled = 0,
+ FifosEnabled = 1
+ ]
+ ],
+
+ /// Control Register
+ CR [
+ /// Receive enable. If this bit is set to 1, the receive section of the UART is enabled.
+ /// Data reception occurs for UART signals. When the UART is disabled in the middle of
+ /// reception, it completes the current character before stopping.
+ RXE OFFSET(9) NUMBITS(1) [
+ Disabled = 0,
+ Enabled = 1
+ ],
+
+ /// Transmit enable. If this bit is set to 1, the transmit section of the UART is enabled.
+ /// Data transmission occurs for UART signals. When the UART is disabled in the middle of
+ /// transmission, it completes the current character before stopping.
+ TXE OFFSET(8) NUMBITS(1) [
+ Disabled = 0,
+ Enabled = 1
+ ],
+
+ /// UART enable
+ UARTEN OFFSET(0) NUMBITS(1) [
+ /// If the UART is disabled in the middle of transmission or reception, it completes the
+ /// current character before stopping.
+ Disabled = 0,
+ Enabled = 1
+ ]
+ ],
+
+ /// Interrupt Clear Register
+ ICR [
+ /// Meta field for all pending interrupts
+ ALL OFFSET(0) NUMBITS(11) []
+ ]
+}
+
+register_structs! {
+ #[allow(non_snake_case)]
+ RegisterBlock {
+ (0x00 => DR: ReadWrite),
+ (0x04 => _reserved1),
+ (0x18 => FR: ReadOnly),
+ (0x1c => _reserved2),
+ (0x24 => IBRD: WriteOnly),
+ (0x28 => FBRD: WriteOnly),
+ (0x2c => LCRH: WriteOnly),
+ (0x30 => CR: WriteOnly),
+ (0x34 => _reserved3),
+ (0x44 => ICR: WriteOnly),
+ (0x48 => @END),
+ }
+}
+
+/// The driver's mutex protected part.
+pub struct PL011UartInner {
+ base_addr: usize,
+ chars_written: usize,
+}
+
+/// Deref to RegisterBlock.
+///
+/// Allows writing
+/// ```
+/// self.DR.read()
+/// ```
+/// instead of something along the lines of
+/// ```
+/// unsafe { (*PL011UartInner::ptr()).DR.read() }
+/// ```
+impl ops::Deref for PL011UartInner {
+ type Target = RegisterBlock;
+
+ fn deref(&self) -> &Self::Target {
+ unsafe { &*self.ptr() }
+ }
+}
+
+impl PL011UartInner {
+ pub const unsafe fn new(base_addr: usize) -> PL011UartInner {
+ PL011UartInner {
+ base_addr,
+ chars_written: 0,
+ }
+ }
+
+ /// Set up baud rate and characteristics.
+ ///
+ /// Results in 8N1 and 115200 baud (if the clk has been previously set to 4 MHz by the
+ /// firmware).
+ pub fn init(&self) {
+ // Turn it off temporarily.
+ self.CR.set(0);
+
+ self.ICR.write(ICR::ALL::CLEAR);
+ self.IBRD.write(IBRD::IBRD.val(26)); // Results in 115200 baud for UART Clk of 48 MHz.
+ self.FBRD.write(FBRD::FBRD.val(3));
+ self.LCRH
+ .write(LCRH::WLEN::EightBit + LCRH::FEN::FifosEnabled); // 8N1 + Fifo on
+ self.CR
+ .write(CR::UARTEN::Enabled + CR::TXE::Enabled + CR::RXE::Enabled);
+ }
+
+ /// Return a pointer to the register block.
+ fn ptr(&self) -> *const RegisterBlock {
+ self.base_addr as *const _
+ }
+
+ /// Send a character.
+ fn write_char(&mut self, c: char) {
+ // Spin while TX FIFO full is set, waiting for an empty slot.
+ while self.FR.matches_all(FR::TXFF::SET) {
+ arch::nop();
+ }
+
+ // Write the character to the buffer.
+ self.DR.set(c as u32);
+ }
+}
+
+/// Implementing `core::fmt::Write` enables usage of the `format_args!` macros, which in turn are
+/// used to implement the `kernel`'s `print!` and `println!` macros. By implementing `write_str()`,
+/// we get `write_fmt()` automatically.
+///
+/// The function takes an `&mut self`, so it must be implemented for the inner struct.
+///
+/// See [`src/print.rs`].
+///
+/// [`src/print.rs`]: ../../print/index.html
+impl fmt::Write for PL011UartInner {
+ fn write_str(&mut self, s: &str) -> fmt::Result {
+ for c in s.chars() {
+ // Convert newline to carrige return + newline.
+ if c == '\n' {
+ self.write_char('\r')
+ }
+
+ self.write_char(c);
+ }
+
+ self.chars_written += s.len();
+
+ Ok(())
+ }
+}
+
+//--------------------------------------------------------------------------------------------------
+// Export the inner struct so that BSPs can use it for the panic handler
+//--------------------------------------------------------------------------------------------------
+pub use PL011UartInner as PanicUart;
+
+//--------------------------------------------------------------------------------------------------
+// BSP-public
+//--------------------------------------------------------------------------------------------------
+
+/// The driver's main struct.
+pub struct PL011Uart {
+ inner: NullLock,
+}
+
+impl PL011Uart {
+ /// # Safety
+ ///
+ /// The user must ensure to provide the correct `base_addr`.
+ pub const unsafe fn new(base_addr: usize) -> PL011Uart {
+ PL011Uart {
+ inner: NullLock::new(PL011UartInner::new(base_addr)),
+ }
+ }
+}
+
+//--------------------------------------------------------------------------------------------------
+// OS interface implementations
+//--------------------------------------------------------------------------------------------------
+use interface::sync::Mutex;
+
+impl interface::driver::DeviceDriver for PL011Uart {
+ fn compatible(&self) -> &str {
+ "PL011Uart"
+ }
+
+ fn init(&self) -> interface::driver::Result {
+ let mut r = &self.inner;
+ r.lock(|inner| inner.init());
+
+ Ok(())
+ }
+}
+
+impl interface::console::Write for PL011Uart {
+ /// Passthrough of `args` to the `core::fmt::Write` implementation, but guarded by a Mutex to
+ /// serialize access.
+ fn write_char(&self, c: char) {
+ let mut r = &self.inner;
+ r.lock(|inner| inner.write_char(c));
+ }
+
+ fn write_fmt(&self, args: core::fmt::Arguments) -> fmt::Result {
+ // Fully qualified syntax for the call to `core::fmt::Write::write:fmt()` to increase
+ // readability.
+ let mut r = &self.inner;
+ r.lock(|inner| fmt::Write::write_fmt(inner, args))
+ }
+}
+
+impl interface::console::Read for PL011Uart {
+ fn read_char(&self) -> char {
+ let mut r = &self.inner;
+ r.lock(|inner| {
+ // Spin while RX FIFO empty is set.
+ while inner.FR.matches_all(FR::RXFE::SET) {
+ arch::nop();
+ }
+
+ // Read one character.
+ let mut ret = inner.DR.get() as u8 as char;
+
+ // Convert carrige return to newline.
+ if ret == '\r' {
+ ret = '\n'
+ }
+
+ ret
+ })
+ }
+}
+
+impl interface::console::Statistics for PL011Uart {
+ fn chars_written(&self) -> usize {
+ let mut r = &self.inner;
+ r.lock(|inner| inner.chars_written)
+ }
+}
diff -uNr 05_safe_globals/src/bsp/driver/bcm.rs 06_drivers_gpio_uart/src/bsp/driver/bcm.rs
--- 05_safe_globals/src/bsp/driver/bcm.rs
+++ 06_drivers_gpio_uart/src/bsp/driver/bcm.rs
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+//
+// Copyright (c) 2018-2019 Andre Richter
+
+//! BCM driver top level.
+
+mod bcm2xxx_gpio;
+mod bcm2xxx_pl011_uart;
+
+pub use bcm2xxx_gpio::GPIO;
+pub use bcm2xxx_pl011_uart::{PL011Uart, PanicUart};
diff -uNr 05_safe_globals/src/bsp/driver.rs 06_drivers_gpio_uart/src/bsp/driver.rs
--- 05_safe_globals/src/bsp/driver.rs
+++ 06_drivers_gpio_uart/src/bsp/driver.rs
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+//
+// Copyright (c) 2018-2019 Andre Richter
+
+//! Drivers.
+
+#[cfg(any(feature = "bsp_rpi3", feature = "bsp_rpi4"))]
+mod bcm;
+
+#[cfg(any(feature = "bsp_rpi3", feature = "bsp_rpi4"))]
+pub use bcm::*;
diff -uNr 05_safe_globals/src/bsp/rpi/memory_map.rs 06_drivers_gpio_uart/src/bsp/rpi/memory_map.rs
--- 05_safe_globals/src/bsp/rpi/memory_map.rs
+++ 06_drivers_gpio_uart/src/bsp/rpi/memory_map.rs
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+//
+// Copyright (c) 2018-2019 Andre Richter
+
+//! The board's memory map.
+
+/// Physical devices.
+#[rustfmt::skip]
+pub mod mmio {
+ #[cfg(feature = "bsp_rpi3")]
+ pub const BASE: usize = 0x3F00_0000;
+
+ #[cfg(feature = "bsp_rpi4")]
+ pub const BASE: usize = 0xFE00_0000;
+
+ pub const GPIO_BASE: usize = BASE + 0x0020_0000;
+ pub const PL011_UART_BASE: usize = BASE + 0x0020_1000;
+}
diff -uNr 05_safe_globals/src/bsp/rpi.rs 06_drivers_gpio_uart/src/bsp/rpi.rs
--- 05_safe_globals/src/bsp/rpi.rs
+++ 06_drivers_gpio_uart/src/bsp/rpi.rs
@@ -4,114 +4,68 @@
//! Board Support Package for the Raspberry Pi.
-use crate::{arch::sync::NullLock, interface};
+mod memory_map;
+
+use super::driver;
+use crate::interface;
use core::fmt;
pub const BOOT_CORE_ID: u64 = 0;
pub const BOOT_CORE_STACK_START: u64 = 0x80_000;
-/// A mystical, magical device for generating QEMU output out of the void.
-///
-/// The mutex protected part.
-struct QEMUOutputInner {
- chars_written: usize,
-}
-
-impl QEMUOutputInner {
- const fn new() -> QEMUOutputInner {
- QEMUOutputInner { chars_written: 0 }
- }
-
- /// Send a character.
- fn write_char(&mut self, c: char) {
- unsafe {
- core::ptr::write_volatile(0x3F20_1000 as *mut u8, c as u8);
- }
- }
-}
-
-/// Implementing `core::fmt::Write` enables usage of the `format_args!` macros, which in turn are
-/// used to implement the `kernel`'s `print!` and `println!` macros. By implementing `write_str()`,
-/// we get `write_fmt()` automatically.
-///
-/// The function takes an `&mut self`, so it must be implemented for the inner struct.
-///
-/// See [`src/print.rs`].
-///
-/// [`src/print.rs`]: ../../print/index.html
-impl fmt::Write for QEMUOutputInner {
- fn write_str(&mut self, s: &str) -> fmt::Result {
- for c in s.chars() {
- // Convert newline to carrige return + newline.
- if c == '\n' {
- self.write_char('\r')
- }
-
- self.write_char(c);
- }
-
- self.chars_written += s.len();
-
- Ok(())
- }
-}
-
//--------------------------------------------------------------------------------------------------
-// BSP-public
+// Global BSP driver instances
//--------------------------------------------------------------------------------------------------
-/// The main struct.
-pub struct QEMUOutput {
- inner: NullLock,
-}
-
-impl QEMUOutput {
- pub const fn new() -> QEMUOutput {
- QEMUOutput {
- inner: NullLock::new(QEMUOutputInner::new()),
- }
- }
-}
+static GPIO: driver::GPIO = unsafe { driver::GPIO::new(memory_map::mmio::GPIO_BASE) };
+static PL011_UART: driver::PL011Uart =
+ unsafe { driver::PL011Uart::new(memory_map::mmio::PL011_UART_BASE) };
//--------------------------------------------------------------------------------------------------
-// OS interface implementations
+// Implementation of the kernel's BSP calls
//--------------------------------------------------------------------------------------------------
-/// Passthrough of `args` to the `core::fmt::Write` implementation, but guarded by a Mutex to
-/// serialize access.
-impl interface::console::Write for QEMUOutput {
- fn write_fmt(&self, args: core::fmt::Arguments) -> fmt::Result {
- use interface::sync::Mutex;
-
- // Fully qualified syntax for the call to `core::fmt::Write::write:fmt()` to increase
- // readability.
- let mut r = &self.inner;
- r.lock(|inner| fmt::Write::write_fmt(inner, args))
+/// Board identification.
+pub fn board_name() -> &'static str {
+ #[cfg(feature = "bsp_rpi3")]
+ {
+ "Raspberry Pi 3"
}
-}
-impl interface::console::Read for QEMUOutput {}
-
-impl interface::console::Statistics for QEMUOutput {
- fn chars_written(&self) -> usize {
- use interface::sync::Mutex;
-
- let mut r = &self.inner;
- r.lock(|inner| inner.chars_written)
+ #[cfg(feature = "bsp_rpi4")]
+ {
+ "Raspberry Pi 4"
}
}
-//--------------------------------------------------------------------------------------------------
-// Global instances
-//--------------------------------------------------------------------------------------------------
+/// Return a reference to a `console::All` implementation.
+pub fn console() -> &'static impl interface::console::All {
+ &PL011_UART
+}
-static QEMU_OUTPUT: QEMUOutput = QEMUOutput::new();
+/// In case of a panic, the panic handler uses this function to take a last shot at printing
+/// something before the system is halted.
+///
+/// # Safety
+///
+/// - Use only for printing during a panic.
+pub unsafe fn panic_console_out() -> impl fmt::Write {
+ let uart = driver::PanicUart::new(memory_map::mmio::PL011_UART_BASE);
+ uart.init();
+ uart
+}
-//--------------------------------------------------------------------------------------------------
-// Implementation of the kernel's BSP calls
-//--------------------------------------------------------------------------------------------------
+/// Return an array of references to all `DeviceDriver` compatible `BSP` drivers.
+///
+/// # Safety
+///
+/// The order of devices is the order in which `DeviceDriver::init()` is called.
+pub fn device_drivers() -> [&'static dyn interface::driver::DeviceDriver; 2] {
+ [&GPIO, &PL011_UART]
+}
-/// Return a reference to a `console::All` implementation.
-pub fn console() -> &'static impl interface::console::All {
- &QEMU_OUTPUT
+/// BSP initialization code that runs after driver init.
+pub fn post_driver_init() {
+ // Configure PL011Uart's output pins.
+ GPIO.map_pl011_uart();
}
diff -uNr 05_safe_globals/src/bsp.rs 06_drivers_gpio_uart/src/bsp.rs
--- 05_safe_globals/src/bsp.rs
+++ 06_drivers_gpio_uart/src/bsp.rs
@@ -4,6 +4,8 @@
//! Conditional exporting of Board Support Packages.
+mod driver;
+
#[cfg(any(feature = "bsp_rpi3", feature = "bsp_rpi4"))]
mod rpi;
diff -uNr 05_safe_globals/src/interface.rs 06_drivers_gpio_uart/src/interface.rs
--- 05_safe_globals/src/interface.rs
+++ 06_drivers_gpio_uart/src/interface.rs
@@ -24,6 +24,7 @@
/// Console write functions.
pub trait Write {
+ fn write_char(&self, c: char);
fn write_fmt(&self, args: fmt::Arguments) -> fmt::Result;
}
@@ -83,3 +84,20 @@
fn lock(&mut self, f: impl FnOnce(&mut Self::Data) -> R) -> R;
}
}
+
+/// Driver interfaces.
+pub mod driver {
+ /// Driver result type, e.g. for indicating successful driver init.
+ pub type Result = core::result::Result<(), ()>;
+
+ /// Device Driver functions.
+ pub trait DeviceDriver {
+ /// Return a compatibility string for identifying the driver.
+ fn compatible(&self) -> &str;
+
+ /// Called by the kernel to bring up the device.
+ fn init(&self) -> Result {
+ Ok(())
+ }
+ }
+}
diff -uNr 05_safe_globals/src/main.rs 06_drivers_gpio_uart/src/main.rs
--- 05_safe_globals/src/main.rs
+++ 06_drivers_gpio_uart/src/main.rs
@@ -41,16 +41,48 @@
/// Early init code.
///
+/// Concerned with with initializing `BSP` and `arch` parts.
+///
/// # Safety
///
/// - Only a single core must be active and running this function.
+/// - The init calls in this function must appear in the correct order.
unsafe fn kernel_init() -> ! {
- use interface::console::Statistics;
+ for i in bsp::device_drivers().iter() {
+ if let Err(()) = i.init() {
+ panic!("Error loading driver: {}", i.compatible())
+ }
+ }
+ bsp::post_driver_init();
+ // println! is usable from here on.
+
+ // Transition from unsafe to safe.
+ kernel_main()
+}
+
+/// The main function running after the early init.
+fn kernel_main() -> ! {
+ use interface::console::All;
+
+ // UART should be functional now. Wait for user to hit Enter.
+ loop {
+ if bsp::console().read_char() == '\n' {
+ break;
+ }
+ }
+
+ println!("[0] Booting on: {}", bsp::board_name());
- println!("[0] Hello from pure Rust!");
+ println!("[1] Drivers loaded:");
+ for (i, driver) in bsp::device_drivers().iter().enumerate() {
+ println!(" {}. {}", i + 1, driver.compatible());
+ }
- println!("[1] Chars written: {}", bsp::console().chars_written());
+ println!("[2] Chars written: {}", bsp::console().chars_written());
+ println!("[3] Echoing input now");
- println!("[2] Stopping here.");
- arch::wait_forever()
+ loop {
+ let c = bsp::console().read_char();
+ bsp::console().write_char(c);
+ }
}
diff -uNr 05_safe_globals/src/panic_wait.rs 06_drivers_gpio_uart/src/panic_wait.rs
--- 05_safe_globals/src/panic_wait.rs
+++ 06_drivers_gpio_uart/src/panic_wait.rs
@@ -4,15 +4,31 @@
//! A panic handler that infinitely waits.
-use crate::{arch, println};
-use core::panic::PanicInfo;
+use crate::{arch, bsp};
+use core::{fmt, panic::PanicInfo};
+
+fn _panic_print(args: fmt::Arguments) {
+ use fmt::Write;
+
+ unsafe { bsp::panic_console_out().write_fmt(args).unwrap() };
+}
+
+/// Prints with a newline - only use from the panic handler.
+///
+/// Carbon copy from https://doc.rust-lang.org/src/std/macros.rs.html
+#[macro_export]
+macro_rules! panic_println {
+ ($($arg:tt)*) => ({
+ _panic_print(format_args_nl!($($arg)*));
+ })
+}
#[panic_handler]
fn panic(info: &PanicInfo) -> ! {
if let Some(args) = info.message() {
- println!("Kernel panic: {}", args);
+ panic_println!("Kernel panic: {}", args);
} else {
- println!("Kernel panic!");
+ panic_println!("Kernel panic!");
}
arch::wait_forever()
```