add delay between IOs

4 files changed, 34 insertions, 0 deletions

diff --git a/src/arch/x86_64/asm/misc.s b/src/arch/x86_64/asm/misc.s
new file mode 100644
index 0000000..fc5aa90
--- /dev/null
+++ b/src/arch/x86_64/asm/misc.s
@@ -0,0 +1,11 @@
+; place for misc code, before they find better places to live..
+
+[GLOBAL _delay]
+
+[SECTION .text]
+
+_delay:
+    jmp .dummy
+.dummy:
+    ret
+
diff --git a/src/arch/x86_64/misc.rs b/src/arch/x86_64/misc.rs
new file mode 100644
index 0000000..c007d99
--- /dev/null
+++ b/src/arch/x86_64/misc.rs
@@ -0,0 +1,17 @@
+// wrappers for misc. architectural code
+// before they find better place to go.
+// asm code goes to asm/misc.s
+
+extern "C" {
+    fn _delay();
+}
+
+#[inline(always)]
+
+// delays for several cycles. Used to fill sequantial IO commands
+// (for devices to react)
+pub fn delay() {
+    unsafe {
+        _delay();
+    }                
+}
diff --git a/src/arch/x86_64/mod.rs b/src/arch/x86_64/mod.rs
index ef06437..f48c7fd 100644
--- a/src/arch/x86_64/mod.rs
+++ b/src/arch/x86_64/mod.rs
@@ -3,3 +3,4 @@ pub mod pic;
 pub mod pit;
 pub mod plugbox;
 pub mod cpu;
+pub mod misc;
diff --git a/src/machine/cgascr.rs b/src/machine/cgascr.rs
index 2748e67..dd019d7 100644
--- a/src/machine/cgascr.rs
+++ b/src/machine/cgascr.rs
@@ -1,4 +1,5 @@
 use crate::arch::x86_64::io_port::*;
+use crate::arch::x86_64::misc::*;
 
 const CGA_BUFFER_START:*mut u8 = 0xb8000 as *mut u8;
 const IR_PORT:u16 = 0x3d4;
@@ -44,10 +45,14 @@ impl CGAScreen{
         
         // set lower byte
         outb(IR_PORT, 15 as u8);
+        delay();
         outb(DR_PORT, offset as u8);
+        delay();
         // set higher byte
         outb(IR_PORT, 14 as u8);
+        delay();
         outb(DR_PORT, (offset >> 8) as u8);
+        delay();
 
     }