EOI acknoledgment of PICs, also showing PIT events are coming in

4 files changed, 41 insertions, 11 deletions

diff --git a/src/.gdbinit b/src/.gdbinit
index 94edd63..12d2269 100644
--- a/src/.gdbinit
+++ b/src/.gdbinit
@@ -2,4 +2,4 @@ target remote localhost:1234
 symbol-file kernel.sym
 break entry
 c
-wh
+wh 10
diff --git a/src/interrupts.c b/src/interrupts.c
index c04eb59..feb3aab 100644
--- a/src/interrupts.c
+++ b/src/interrupts.c
@@ -54,6 +54,9 @@
 #define ICW4_BUFFER 0x08
 #define ICW4_FULLY_NESTED 0x10
 
+// OCW2
+#define OCW2_EOI 0x20	// non-specific End Of Interrupt
+
 // must be global: when called via assembly code we loose the context
 // of the interrupt handler structure
 interrupt_t interrupt;
@@ -92,7 +95,8 @@ void interrupts_init( interrupt_t *interrupt )
 	port8_write( &interrupt->PIC_master_control, ICW1_ICW4 | ICW1_INIT );
 	port8_write( &interrupt->PIC_slave_control, ICW1_ICW4 | ICW1_INIT );
 	
-	// set IRQ base of both PICS (ICW2)
+	// set IRQ base of both PICS (ICW2), remap them so they
+	// don't collide with CPU exceptions (this is true after 0x20)
 	port8_write( &interrupt->PIC_master_data, ICW2_IRQ_BASE_MASTER );
 	port8_write( &interrupt->PIC_slave_data, ICW2_IRQ_BASE_SLAVE );
 	
@@ -104,6 +108,13 @@ void interrupts_init( interrupt_t *interrupt )
 	// TODO: use buffered mode later?
 	port8_write( &interrupt->PIC_master_data, ICW4_8086 );
 	port8_write( &interrupt->PIC_slave_data, ICW4_8086 );
+
+	// done, enable all IRQs by setting the interrupt mask register
+	// 0 for all bits. We are not interested in the old state of
+	// the mask as we are initializing in protected mode
+	// TODO: later we will mask uninmported interrupts maybe?
+	port8_write( &interrupt->PIC_master_data, 0 );
+	port8_write( &interrupt->PIC_slave_data, 0 );
 		
 	// tell CPU where the IDT is
 	interrupt->idt_pointer.size = 256 * sizeof( interrupt_gate_descriptor_t ) - 1;
@@ -137,9 +148,11 @@ uint32_t interrupts_exception_division_by_zero( uint32_t esp )
 	return esp;
 }
 
+static int pit_counter = 0;
 uint32_t interrupts_interrupt_PIT( uint32_t esp )
 {
-	puts( "PIT PIT PIT PIT PIT PIT PIT" );
+	pit_counter++;
+	printf( "PIT PIT PIT PIT PIT PIT PIT %d", pit_counter );
 	return esp;
 }
 
@@ -154,12 +167,20 @@ uint32_t interrupts_handle_interrupt( uint8_t interrupt_no, uint32_t esp )
 {
 	interrupt_handler_t handler = interrupt.interrupt_handler[interrupt_no];
 	
-	if( handler != NULL ) {
-		uint32_t new_esp = handler( esp );
-		return new_esp;
+	if( handler == NULL ) {
+		kernel_panic( "Unhandled interrupt 0x%X with ESP 0x%X\n", interrupt_no, esp );
 	}
-	
-	kernel_panic( "Unhandled interrupt 0x%X with ESP 0x%X\n", interrupt_no, esp );
-	
-	return esp;
+
+	uint32_t new_esp = handler( esp );
+
+	// send ACK to PIC for hardware interrups
+	if( interrupt_no >= IRQ_BASE && interrupt_no <= IRQ_BASE + 16 ) {
+		if( interrupt_no < IRQ_BASE + 8 ) {
+			port8_write( &interrupt.PIC_master_control, OCW2_EOI );
+		} else {
+			port8_write( &interrupt.PIC_slave_control, OCW2_EOI );
+		}
+	}
+
+	return new_esp;
 }
diff --git a/src/interrupts.h b/src/interrupts.h
index 0b514ea..64f1b43 100644
--- a/src/interrupts.h
+++ b/src/interrupts.h
@@ -47,7 +47,9 @@ typedef struct {
 	interrupt_descriptor_table_pointer_t idt_pointer;
 	interrupt_gate_descriptor_t descriptor_table[NOF_INTERRUPTS];
 	interrupt_handler_t interrupt_handler[NOF_INTERRUPTS];
+	// PIC master control register: command and status register
 	port8_t PIC_master_control;
+	// PIC master data register: interrupt mask and data register
 	port8_t PIC_master_data;
 	// since PC/AT we always have a slave PIC, we don't support the PC/XT architecture
 	// with just one PIC
diff --git a/src/kernel.c b/src/kernel.c
index ceb1380..8759f18 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -52,10 +52,17 @@ void entry( void )
 	int y_pos = vga_get_cursor_y( &vga );
 	int x_pos = vga_get_cursor_x( &vga );
 	int i = 0;
-	for( i = 0; i < 10000; i++ ) {
+	for( i = 0; i < 100000; i++ ) {
 		if( i % 1000 == 1 ) {
 			vga_put_char_at( &vga, x_pos, y_pos, '.' );
 			x_pos++;
+			if( x_pos > vga.res_x ) {
+				x_pos = 0;
+				y_pos++;
+				if( y_pos > vga.res_y ) {
+					y_pos = 0;
+				}
+			}
 //			serial_put_char( &serial, '.' );
 //~ int y = 0;
 //~ int x = 12 / y;