Use ownership to handle sdram memory

Author: oli-obk

src/bin/async-await.rs

@@ -103,17 +103,17 @@ fn run() -> ! {
     init::init_systick(Hz(100), &mut systick, &rcc);
     systick.enable_interrupt();
 
-    init::init_sdram(&mut rcc, &mut fmc);
-    let mut lcd = init::init_lcd(&mut ltdc, &mut rcc);
+    let sdram = init::init_sdram(&mut rcc, &mut fmc);
+    let (mut lcd, _sdram) = lcd::init(&mut ltdc, &mut rcc, sdram);
     pins.display_enable.set(true);
     pins.backlight.set(true);
 
     // Initialize the allocator BEFORE you use it
     unsafe { ALLOCATOR.init(cortex_m_rt::heap_start() as usize, HEAP_SIZE) }
 
     lcd.set_background_color(Color::from_hex(0x006600));
-    let layer_1 = lcd.layer_1().unwrap();
-    let mut layer_2 = lcd.layer_2().unwrap();
+    let layer_1 = lcd.layer_1.take().unwrap();
+    let mut layer_2 = lcd.layer_2.take().unwrap();
 
     layer_2.clear();
 

src/bin/polling.rs

@@ -87,13 +87,13 @@ fn main() -> ! {
     init::init_systick(Hz(100), &mut systick, &rcc);
     systick.enable_interrupt();
 
-    init::init_sdram(&mut rcc, &mut fmc);
-    let mut lcd = init::init_lcd(&mut ltdc, &mut rcc);
+    let sdram = init::init_sdram(&mut rcc, &mut fmc);
+    let (mut lcd, _sdram) = lcd::init(&mut ltdc, &mut rcc, sdram);
     pins.display_enable.set(true);
     pins.backlight.set(true);
 
-    let mut layer_1 = lcd.layer_1().unwrap();
-    let mut layer_2 = lcd.layer_2().unwrap();
+    let mut layer_1 = lcd.layer_1.take().unwrap();
+    let mut layer_2 = lcd.layer_2.take().unwrap();
 
     layer_1.clear();
     layer_2.clear();

src/init/mod.rs

@@ -1,9 +1,8 @@
 //! Provides various hardware initialization functions.
 
 use crate::i2c::{self, I2C};
-use crate::lcd::{self, Lcd};
 use crate::system_clock;
-use stm32f7::stm32f7x6::{self as device, FLASH, FMC, LTDC, PWR, RCC, SAI2, SYST};
+use stm32f7::stm32f7x6::{self as device, FLASH, FMC, PWR, RCC, SAI2, SYST};
 
 pub use self::pins::init as pins;
 pub use self::pins::Pins;
@@ -146,10 +145,19 @@ pub fn enable_syscfg(rcc: &mut RCC) {
     let _unused = rcc.apb2enr.read();
 }
 
+static mut SDRAM_INITIALIZED: bool = false;
+
 /// Initializes the SDRAM, which makes more memory accessible.
 ///
 /// This is a prerequisite for using the LCD.
-pub fn init_sdram(rcc: &mut RCC, fmc: &mut FMC) {
+pub fn init_sdram(rcc: &mut RCC, fmc: &mut FMC) -> &'static mut [volatile::Volatile<u8>] {
+
+    // ensures that we don't do this twice and end up with two `&'static mut` to the same memory
+    unsafe {
+        assert!(!SDRAM_INITIALIZED);
+        SDRAM_INITIALIZED = true;
+    }
+
     #[allow(dead_code)]
     #[derive(Debug, Clone, Copy)]
     enum Bank {
@@ -221,7 +229,7 @@ pub fn init_sdram(rcc: &mut RCC, fmc: &mut FMC) {
     rcc.ahb3rstr.modify(|_, w| w.fmcrst().reset());
     rcc.ahb3rstr.modify(|_, w| w.fmcrst().clear_bit());
 
-    // SDRAM contol register
+    // SDRAM control register
     fmc.sdcr1.modify(|_, w| unsafe {
         w.nc().bits(8 - 8); // number_of_column_address_bits
         w.nr().bits(12 - 11); // number_of_row_address_bits
@@ -272,30 +280,32 @@ pub fn init_sdram(rcc: &mut RCC, fmc: &mut FMC) {
         w
     });
 
-    // test sdram
-    use core::ptr;
+    let sdram_start: usize = 0xC000_0000;
+    let sdram_len: usize = 64 / 8 * 1024 * 1024; // 64 Mbit according to packaging
+
+    {
+        // test sdram
+        use core::ptr;
 
-    let ptr1 = 0xC000_0000 as *mut u32;
-    let ptr2 = 0xC053_6170 as *mut u32;
-    let ptr3 = 0xC07F_FFFC as *mut u32;
+        let ptr1 = sdram_start as *mut u32;
+        let ptr2 = (sdram_start + 0x0053_6170) as *mut u32;
+        let ptr3 = (sdram_start + sdram_len - 4) as *mut u32;
 
+        unsafe {
+            ptr::write_volatile(ptr1, 0xcafe_babe);
+            ptr::write_volatile(ptr2, 0xdead_beaf);
+            ptr::write_volatile(ptr3, 0x0dea_fbee);
+            assert_eq!(ptr::read_volatile(ptr1), 0xcafe_babe);
+            assert_eq!(ptr::read_volatile(ptr2), 0xdead_beaf);
+            assert_eq!(ptr::read_volatile(ptr3), 0x0dea_fbee);
+        }
+    }
+    // this block's safety is guaranteed by SDRAM_INITIALIZED check at the start of this function
     unsafe {
-        ptr::write_volatile(ptr1, 0xcafe_babe);
-        ptr::write_volatile(ptr2, 0xdead_beaf);
-        ptr::write_volatile(ptr3, 0x0dea_fbee);
-        assert_eq!(ptr::read_volatile(ptr1), 0xcafe_babe);
-        assert_eq!(ptr::read_volatile(ptr2), 0xdead_beaf);
-        assert_eq!(ptr::read_volatile(ptr3), 0x0dea_fbee);
+        core::slice::from_raw_parts_mut(sdram_start as *mut volatile::Volatile<u8>, sdram_len)
     }
 }
 
-/// Initializes the LCD.
-///
-/// This function is equivalent to [`lcd::init`](crate::lcd::init::init).
-pub fn init_lcd<'a>(ltdc: &'a mut LTDC, rcc: &mut RCC) -> Lcd<'a> {
-    lcd::init(ltdc, rcc)
-}
-
 /// Initializes the I2C3 bus.
 ///
 /// This function is equivalent to [`i2c::init`](crate::i2c::init).

src/lcd/init.rs

@@ -3,12 +3,16 @@ use stm32f7::stm32f7x6::{LTDC, RCC};
 
 /// Initializes the LCD controller.
 ///
-/// The SDRAM must be initialized before this function is called. See the
-/// [`init_sdram`] function for more information.
+/// Needs memory for the screen buffers. On stm32f7 this is usually done via SDRAM.
+/// The SDRAM is initialized via the [`init_sdram`] function.
 ///
 /// [`init_sdram`]: crate::init::init_sdram
-pub fn init<'a>(ltdc: &'a mut LTDC, rcc: &mut RCC) -> Lcd<'a> {
-    use crate::lcd::{self, LAYER_1_START, LAYER_2_START};
+pub fn init<'a>(
+    ltdc: &'a mut LTDC,
+    rcc: &mut RCC,
+    mem: &'static mut [volatile::Volatile<u8>],
+) -> (Lcd<'a>, &'static mut [volatile::Volatile<u8>]) {
+    use crate::lcd;
     const HEIGHT: u16 = lcd::HEIGHT as u16;
     const WIDTH: u16 = lcd::WIDTH as u16;
     const LAYER_1_OCTETS_PER_PIXEL: u16 = lcd::LAYER_1_OCTETS_PER_PIXEL as u16;
@@ -152,11 +156,14 @@ pub fn init<'a>(ltdc: &'a mut LTDC, rcc: &mut RCC) -> Lcd<'a> {
         w
     });
 
+    let (layer1, mem) = mem.split_at_mut(lcd::LAYER_1_LENGTH);
+    let (layer2, mem) = mem.split_at_mut(lcd::LAYER_2_LENGTH);
+
     // configure color frame buffer start address
     ltdc.l1cfbar
-        .modify(|_, w| unsafe { w.cfbadd().bits(LAYER_1_START as u32) });
+        .modify(|_, w| unsafe { w.cfbadd().bits(layer1.as_mut_ptr() as usize as u32) });
     ltdc.l2cfbar
-        .modify(|_, w| unsafe { w.cfbadd().bits(LAYER_2_START as u32) });
+        .modify(|_, w| unsafe { w.cfbadd().bits(layer2.as_mut_ptr() as usize as u32) });
 
     // configure color frame buffer line length and pitch
     ltdc.l1cfblr.modify(|_, w| unsafe {
@@ -180,8 +187,9 @@ pub fn init<'a>(ltdc: &'a mut LTDC, rcc: &mut RCC) -> Lcd<'a> {
     ltdc.l1cr.modify(|_, w| w.len().set_bit());
     ltdc.l2cr.modify(|_, w| w.len().set_bit().cluten().set_bit());
 
-    // reload shadow registers
-    ltdc.srcr.modify(|_, w| w.imr().set_bit()); // IMMEDIATE_RELOAD
+    let mut lcd = Lcd::new(ltdc, layer1, layer2);
+
+    lcd.reload_shadow_registers(); // IMMEDIATE_RELOAD
 
-    Lcd::new(ltdc)
+    (lcd, mem)
 }

src/lcd/mod.rs

@@ -7,7 +7,7 @@ pub use self::color::Color;
 pub use self::init::init;
 pub use self::stdout::init as init_stdout;
 
-use core::{fmt, ptr};
+use core::fmt;
 use stm32f7::stm32f7x6::LTDC;
 
 #[macro_use]
@@ -29,26 +29,31 @@ pub const LAYER_2_OCTETS_PER_PIXEL: usize = 2;
 /// The length of the layer 1 buffer in bytes.
 pub const LAYER_2_LENGTH: usize = HEIGHT * WIDTH * LAYER_2_OCTETS_PER_PIXEL;
 
-/// Start address of the SDRAM where the framebuffers live.
-pub const SDRAM_START: usize = 0xC000_0000;
-/// Start address of the layer 1 framebuffer.
-pub const LAYER_1_START: usize = SDRAM_START;
-/// Start address of the layer 2 framebuffer.
-pub const LAYER_2_START: usize = SDRAM_START + LAYER_1_LENGTH;
-
 /// Represents the LCD and provides methods to access both layers.
 pub struct Lcd<'a> {
     controller: &'a mut LTDC,
-    layer_1_in_use: bool,
-    layer_2_in_use: bool,
+
+    /// A layer with RGB + alpha value
+    ///
+    /// Use `.take()` to get an owned version of this layer.
+    pub layer_1: Option<Layer<FramebufferArgb8888>>,
+
+    /// A layer with alpha + color lookup table index
+    ///
+    /// Use `.take()` to get an owned version of this layer.
+    pub layer_2: Option<Layer<FramebufferAl88>>,
 }
 
 impl<'a> Lcd<'a> {
-    fn new(ltdc: &'a mut LTDC) -> Self {
+    fn new(
+        ltdc: &'a mut LTDC,
+        layer_1: &'static mut [volatile::Volatile<u8>],
+        layer_2: &'static mut [volatile::Volatile<u8>],
+    ) -> Self {
         Self {
             controller: ltdc,
-            layer_1_in_use: false,
-            layer_2_in_use: false,
+            layer_1: Some(Layer { framebuffer: FramebufferArgb8888::new(layer_1) } ),
+            layer_2: Some(Layer { framebuffer: FramebufferAl88::new(layer_2) } ),
         }
     }
 
@@ -71,26 +76,8 @@ impl<'a> Lcd<'a> {
             });
     }
 
-    /// Returns a reference to layer 1.
-    pub fn layer_1(&mut self) -> Option<Layer<FramebufferArgb8888>> {
-        if self.layer_1_in_use {
-            None
-        } else {
-            Some(Layer {
-                framebuffer: FramebufferArgb8888::new(LAYER_1_START),
-            })
-        }
-    }
-
-    /// Returns a reference to layer 2.
-    pub fn layer_2(&mut self) -> Option<Layer<FramebufferAl88>> {
-        if self.layer_2_in_use {
-            None
-        } else {
-            Some(Layer {
-                framebuffer: FramebufferAl88::new(LAYER_2_START),
-            })
-        }
+    fn reload_shadow_registers(&mut self) {
+        self.controller.srcr.modify(|_, w| w.imr().set_bit()); // IMMEDIATE_RELOAD
     }
 }
 
@@ -104,20 +91,23 @@ pub trait Framebuffer {
 ///
 /// It uses 8bits for alpha, red, green, and black respectively, totaling in 32bits per pixel.
 pub struct FramebufferArgb8888 {
-    base_addr: usize,
+    mem: &'static mut [volatile::Volatile<u8>],
 }
 
 impl FramebufferArgb8888 {
-    const fn new(base_addr: usize) -> Self {
-        Self { base_addr }
+    fn new(mem: &'static mut [volatile::Volatile<u8>]) -> Self {
+        Self { mem }
     }
 }
 
 impl Framebuffer for FramebufferArgb8888 {
     fn set_pixel(&mut self, x: usize, y: usize, color: Color) {
         let pixel = y * WIDTH + x;
-        let pixel_ptr = (self.base_addr + pixel * LAYER_1_OCTETS_PER_PIXEL) as *mut u32;
-        unsafe { ptr::write_volatile(pixel_ptr, color.to_argb8888()) };
+        let pixel_idx = pixel * LAYER_1_OCTETS_PER_PIXEL;
+        self.mem[pixel_idx].write(color.alpha);
+        self.mem[pixel_idx + 1].write(color.red);
+        self.mem[pixel_idx + 2].write(color.green);
+        self.mem[pixel_idx + 3].write(color.blue);
     }
 }
 
@@ -126,20 +116,21 @@ impl Framebuffer for FramebufferArgb8888 {
 /// There are 8bits for the alpha channel and 8 bits for specifying a color using a
 /// lookup table. Thus, each pixel is represented by 16bits.
 pub struct FramebufferAl88 {
-    base_addr: usize,
+    mem: &'static mut [volatile::Volatile<u8>],
 }
 
 impl FramebufferAl88 {
-    const fn new(base_addr: usize) -> Self {
-        Self { base_addr }
+    fn new(mem: &'static mut [volatile::Volatile<u8>]) -> Self {
+        Self { mem }
     }
 }
 
 impl Framebuffer for FramebufferAl88 {
     fn set_pixel(&mut self, x: usize, y: usize, color: Color) {
         let pixel = y * WIDTH + x;
-        let pixel_ptr = (self.base_addr + pixel * LAYER_2_OCTETS_PER_PIXEL) as *mut u16;
-        unsafe { ptr::write_volatile(pixel_ptr, u16::from(color.alpha) << 8 | u16::from(color.red)) };
+        let pixel_idx = pixel * LAYER_2_OCTETS_PER_PIXEL;
+        self.mem[pixel_idx].write(color.alpha);
+        self.mem[pixel_idx + 1].write(color.red);
     }
 }