From 45283c43460900d080478973c873339b5db3013e Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sun, 27 Mar 2022 14:47:50 +0200
Subject: kernel/tty: poll only on IRQs, don't burn cycles

---
 src/kernel/arch/i386/tty/serial.c | 4 +---
 src/kernel/arch/i386/tty/tty.c    | 1 +
 2 files changed, 2 insertions(+), 3 deletions(-)

(limited to 'src/kernel/arch/i386/tty')

diff --git a/src/kernel/arch/i386/tty/serial.c b/src/kernel/arch/i386/tty/serial.c
index e77ff5c..054f956 100644
--- a/src/kernel/arch/i386/tty/serial.c
+++ b/src/kernel/arch/i386/tty/serial.c
@@ -14,15 +14,13 @@ static void serial_selftest(void) {
 
 void serial_init(void) {
 	// see https://www.sci.muni.cz/docs/pc/serport.txt
-
-	port_out8(COM1 + 1, 0x00); // disable interrupts, we won't be using them
-
 	// set baud rate divisor
 	port_out8(COM1 + 3, 0b10000000); // enable DLAB
 	port_out8(COM1 + 0, 0x01);       // divisor = 1 (low  byte)
 	port_out8(COM1 + 1, 0x00);       //             (high byte)
 
 	port_out8(COM1 + 3, 0b00000011); // 8 bits, no parity, one stop bit
+	port_out8(COM1 + 1, 0x01);       // enable the Data Ready IRQ
 	port_out8(COM1 + 2, 0b11000111); // enable FIFO with 14-bit trigger level (???)
 
 	serial_selftest();
diff --git a/src/kernel/arch/i386/tty/tty.c b/src/kernel/arch/i386/tty/tty.c
index f3fecf3..a63c16a 100644
--- a/src/kernel/arch/i386/tty/tty.c
+++ b/src/kernel/arch/i386/tty/tty.c
@@ -19,6 +19,7 @@ void tty_read(char *buf, size_t len) {
 		for (;;) {
 			if (serial_poll_read(&buf[i]))		break;
 			if (keyboard_poll_read(&buf[i]))	break;
+			asm("hlt" ::: "memory");
 		}
 	}
 }
-- 
cgit v1.2.3