Allocate Mailboxes from special non-cacheable memory

src/arch/aarch64/memory/bump_allocator.rs

@@ -0,0 +1,100 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2019 Andre Richter <andre.o.richter@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+use crate::println;
+use core::alloc::{Alloc, AllocErr, Layout};
+use core::mem;
+use core::ptr::NonNull;
+use core::slice;
+
+pub struct BumpAllocator {
+    next: usize,
+    pool_end: usize,
+    name: &'static str,
+}
+
+unsafe impl Alloc for BumpAllocator {
+    unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<u8>, AllocErr> {
+        let start = crate::memory::aligned_addr_unchecked(self.next, layout.align());
+        let end = start + layout.size();
+
+        if end <= self.pool_end {
+            self.next = end;
+
+            println!(
+                "[i] {}:\n      Allocated Addr {:#010X} Size {:#X}",
+                self.name,
+                start,
+                layout.size()
+            );
+
+            Ok(NonNull::new_unchecked(start as *mut u8))
+        } else {
+            Err(AllocErr)
+        }
+    }
+
+    // A bump allocator doesn't care
+    unsafe fn dealloc(&mut self, _ptr: NonNull<u8>, _layout: Layout) {}
+}
+
+impl BumpAllocator {
+    pub const fn new(pool_start: usize, pool_end: usize, name: &'static str) -> Self {
+        Self {
+            next: pool_start,
+            pool_end,
+            name,
+        }
+    }
+
+    /// Allocate a zeroed slice
+    pub fn alloc_slice_zeroed<'a, T>(
+        &mut self,
+        count_of_items: usize,
+        alignment: usize,
+    ) -> Result<&'a mut [T], ()> {
+        let l;
+        let size_in_byte = count_of_items * mem::size_of::<T>();
+        match Layout::from_size_align(size_in_byte, alignment) {
+            Ok(layout) => l = layout,
+
+            Err(_) => {
+                println!("[e] Layout Error!");
+                return Err(());
+            }
+        }
+
+        let ptr;
+        match unsafe { self.alloc_zeroed(l) } {
+            Ok(i) => ptr = i.as_ptr(),
+
+            Err(_) => {
+                println!("[e] Layout Error!");
+                return Err(());
+            }
+        }
+
+        Ok(unsafe { slice::from_raw_parts_mut(ptr as *mut T, count_of_items) })
+    }
+}

src/arch/aarch64/memory/mod.rs

@@ -5,6 +5,9 @@
 
 // pub use self::area_frame_allocator::AreaFrameAllocator;
 
+mod bump_allocator;
+pub use bump_allocator::BumpAllocator;
+
 pub type PhysicalAddress = usize;
 pub type VirtualAddress = usize;
 

src/arch/aarch64/mmu.rs

@@ -260,11 +260,7 @@ pub unsafe fn init() {
     barrier::isb(barrier::SY);
 
     // Enable the MMU and turn on data and instruction caching.
-    SCTLR_EL1.modify(SCTLR_EL1::M::Enable + SCTLR_EL1::C::NonCacheable + SCTLR_EL1::I::Cacheable);
-
-    // @todo potentially disable both caches here for testing?
-    // Figured: data caching causes these mailbox misreads
-    // Need to allocate mailbox in non-cached memory perhaps for proper hw i/o
+    SCTLR_EL1.modify(SCTLR_EL1::M::Enable + SCTLR_EL1::C::Cacheable + SCTLR_EL1::I::Cacheable);
 
     // Force MMU init to complete before next instruction
     /*

src/main.rs

@@ -9,6 +9,7 @@
 #![feature(core_intrinsics)]
 #![feature(range_contains)]
 #![feature(underscore_const_names)]
+#![feature(allocator_api)]
 #![doc(html_root_url = "https://docs.metta.systems/")]
 #![allow(dead_code)]
 #![allow(unused_assignments)]
@@ -54,6 +55,24 @@ use platform::{
 /// The global console. Output of the print! and println! macros.
 static CONSOLE: sync::NullLock<devices::Console> = sync::NullLock::new(devices::Console::new());
 
+/// The global allocator for DMA-able memory. That is, memory which is tagged
+/// non-cacheable in the page tables.
+static DMA_ALLOCATOR: sync::NullLock<memory::BumpAllocator> =
+    sync::NullLock::new(memory::BumpAllocator::new(
+        memory::map::virt::DMA_HEAP_START as usize,
+        memory::map::virt::DMA_HEAP_END as usize,
+        "Global DMA Allocator",
+        // Try the following arguments instead to see all mailbox operations
+        // fail. It will cause the allocator to use memory that are marked
+        // cacheable and therefore not DMA-safe. The answer from the VideoCore
+        // won't be received by the CPU because it reads an old cached value
+        // that resembles an error case instead.
+
+        // 0x00600000 as usize,
+        // 0x007FFFFF as usize,
+        // "Global Non-DMA Allocator",
+    ));
+
 fn init_jlink_rtt() {
     CONSOLE.lock(|c| {
         c.replace_with(Output::new().into());
@@ -77,7 +96,7 @@ fn init_uart_serial() {
 
     let uart = platform::PL011Uart::new_default();
 
-    let mut mbox = platform::mailbox::Mailbox::new();
+    let mut mbox = platform::mailbox::Mailbox::default();
 
     // uart.init() will reconfigure the GPIO, which causes a race against
     // the MiniUart that is still putting out characters on the physical

src/platform/mailbox.rs

@@ -11,12 +11,14 @@ use register::mmio::*;
 // The address for the buffer needs to be 16-byte aligned
 // so that the VideoCore can handle it properly.
 // The reason is that lowest 4 bits of the address will contain the channel number.
-#[repr(C)]
-#[repr(align(16))]
-pub struct Mailbox {
-    pub buffer: [u32; 36],
+pub struct Mailbox<'a> {
+    pub buffer: &'a mut [u32],
+    base_addr: u32,
 }
 
+const MAILBOX_ALIGNMENT: usize = 16;
+const MAILBOX_ITEMS_COUNT: usize = 36;
+
 // Identity mapped first 1Gb by u-boot
 const MAILBOX_BASE: u32 = BcmHost::get_peripheral_address() + 0xb880;
 // Lowest 4-bits are channel ID.
@@ -292,15 +294,15 @@ fn read(regs: &RegisterBlock, expected: u32, channel: u32) -> Result<()> {
 /// ```
 /// unsafe { (*Mbox::ptr()).STATUS.read() }
 /// ```
-impl Deref for Mailbox {
+impl<'a> Deref for Mailbox<'a> {
     type Target = RegisterBlock;
 
     fn deref(&self) -> &Self::Target {
-        unsafe { &*Self::ptr() }
+        unsafe { &*self.ptr() }
     }
 }
 
-impl core::fmt::Display for Mailbox {
+impl<'a> core::fmt::Display for Mailbox<'a> {
     fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
         let count = self.buffer[0] / 4;
         assert_eq!(self.buffer[0], count * 4);
@@ -312,20 +314,47 @@ impl core::fmt::Display for Mailbox {
     }
 }
 
-impl Default for Mailbox {
+impl<'a> Default for Mailbox<'a> {
     fn default() -> Self {
-        Self::new()
+        Self::new_default().expect("Couldn't allocate a mailbox")
     }
 }
 
-impl Mailbox {
-    pub fn new() -> Mailbox {
-        Mailbox { buffer: [0; 36] }
+impl<'a> Mailbox<'a> {
+    pub fn new_default() -> ::core::result::Result<Mailbox<'a>, ()> {
+        let ret = crate::DMA_ALLOCATOR
+            .lock(|d| d.alloc_slice_zeroed(MAILBOX_ITEMS_COUNT, MAILBOX_ALIGNMENT));
+
+        if ret.is_err() {
+            return Err(());
+        }
+
+        Ok(Mailbox {
+            base_addr: MAILBOX_BASE,
+            buffer: ret.unwrap(),
+        })
+    }
+
+    pub fn new(base_addr: usize) -> ::core::result::Result<Mailbox<'a>, ()> {
+        let ret = crate::DMA_ALLOCATOR
+            .lock(|d| d.alloc_slice_zeroed(MAILBOX_ITEMS_COUNT, MAILBOX_ALIGNMENT));
+
+        if ret.is_err() {
+            return Err(());
+        }
+
+        use core::convert::TryFrom;
+        let base_addr = u32::try_from(base_addr).unwrap();
+
+        Ok(Mailbox {
+            base_addr,
+            buffer: ret.unwrap(),
+        })
     }
 
     /// Returns a pointer to the register block
-    fn ptr() -> *const RegisterBlock {
-        MAILBOX_BASE as *const _
+    fn ptr(&self) -> *const RegisterBlock {
+        self.base_addr as *const _
     }
 
     pub fn write(&self, channel: u32) -> Result<()> {

src/platform/vc.rs

@@ -15,7 +15,7 @@ impl VC {
     // https://www.raspberrypi.org/forums/viewtopic.php?f=72&t=185116
     pub fn init_fb(size: Size2d, depth: u32) -> Option<Display> {
         // Use property channel
-        let mut mbox = Mailbox::new();
+        let mut mbox = Mailbox::default();
 
         /*
          *  * All tags in the request are processed in one operation.