drtio: restore copy_work_buffer for transmission

src/libboard_artiq/src/drtioaux.rs

@@ -6,7 +6,7 @@ use io::{proto::{ProtoRead, ProtoWrite},
          Cursor};
 use libboard_zynq::{time::Milliseconds, timer::GlobalTimer};
 
-pub use crate::drtioaux_proto::Packet;
+pub use crate::drtioaux_proto::{Packet, MAX_PACKET};
 use crate::{drtioaux_proto::Error as ProtocolError, mem::mem::DRTIOAUX_MEM, pl::csr::DRTIOAUX};
 
 #[derive(Debug)]
@@ -35,6 +35,19 @@ impl From<IoError> for Error {
     }
 }
 
+pub fn copy_work_buffer(src: *mut u32, dst: *mut u32, len: isize) {
+    // AXI writes must be 4-byte aligned (drtio proto doesn't care for that),
+    // and AXI burst reads/writes are not implemented yet in gateware
+    // thus the need for a work buffer for transmitting and copying it over
+    unsafe {
+        for i in 0..(len / 4) {
+            *dst.offset(i) = *src.offset(i);
+            //data memory barrier to prevent bursts
+            // dmb();
+        }
+    }
+}
+
 pub fn reset(linkno: u8) {
     let linkno = linkno as usize;
     unsafe {
@@ -115,7 +128,9 @@ where F: FnOnce(&mut [u8]) -> Result<usize, Error> {
     unsafe {
         while (DRTIOAUX[linkno].aux_tx_read)() != 0 {}
         let ptr = DRTIOAUX_MEM[linkno].base as *mut u32;
-        let len = f(slice::from_raw_parts_mut(ptr as *mut u8, 0x400 as usize))?;
+        let mut buf: [u8; MAX_PACKET] = [0; MAX_PACKET];
+        let len = f(&mut buf)?;
+        copy_work_buffer(buf.as_mut_ptr() as *mut u32, ptr, len as isize);
         (DRTIOAUX[linkno].aux_tx_length_write)(len as u16);
         (DRTIOAUX[linkno].aux_tx_write)(1);
         Ok(())

src/libboard_artiq/src/drtioaux_async.rs

@@ -9,8 +9,8 @@ use libboard_zynq::{time::Milliseconds, timer::GlobalTimer};
 use nb;
 use void::Void;
 
-pub use crate::drtioaux_proto::Packet;
+pub use crate::drtioaux_proto::{Packet, MAX_PACKET};
-use crate::{drtioaux::{has_rx_error, Error},
+use crate::{drtioaux::{copy_work_buffer, has_rx_error, Error},
             mem::mem::DRTIOAUX_MEM,
             pl::csr::DRTIOAUX};
 
@@ -102,7 +102,9 @@ where F: FnOnce(&mut [u8]) -> Result<usize, Error> {
     unsafe {
         let _ = block_async!(tx_ready(linkno)).await;
         let ptr = DRTIOAUX_MEM[linkno].base as *mut u32;
-        let len = f(slice::from_raw_parts_mut(ptr as *mut u8, 0x400 as usize))?;
+        let mut buf: [u8; MAX_PACKET] = [0; MAX_PACKET];
+        let len = f(&mut buf)?;
+        copy_work_buffer(buf.as_mut_ptr() as *mut u32, ptr, len as isize);
         (DRTIOAUX[linkno].aux_tx_length_write)(len as u16);
         (DRTIOAUX[linkno].aux_tx_write)(1);
         Ok(())

src/libboard_artiq/src/drtioaux_proto.rs

@@ -1,7 +1,7 @@
 use core_io::{Error as IoError, Read, Write};
 use io::proto::{ProtoRead, ProtoWrite};
 
-const MAX_PACKET: usize = 1024;
+pub const MAX_PACKET: usize = 1024;
 
 // maximum size of arbitrary payloads
 // used by satellite -> master analyzer, subkernel exceptions