optimize the uart get process

Also remove the while in uart_isr. Generally unlimited loop in interrupt handler is not recommended. Signed-off-by: Wang Chen <[email protected]>
zlh20040308 · Mar 28, 2024 · 7df4ae5 · 7df4ae5
1 parent 0cacbd6
commit 7df4ae5
Show file tree

Hide file tree

Showing 6 changed files with 36 additions and 84 deletions.
diff --git a/code/os/06-interrupts/uart.c b/code/os/06-interrupts/uart.c
@@ -125,25 +125,17 @@ void uart_puts(char *s)
 
 int uart_getc(void)
 {
-	if (uart_read_reg(LSR) & LSR_RX_READY){
-		return uart_read_reg(RHR);
-	} else {
-		return -1;
-	}
+	while (0 == (uart_read_reg(LSR) & LSR_RX_READY))
+		;
+	return uart_read_reg(RHR);
 }
 
 /*
  * handle a uart interrupt, raised because input has arrived, called from trap.c.
  */
 void uart_isr(void)
 {
-	while (1) {
-		int c = uart_getc();
-		if (c == -1) {
-			break;
-		} else {
-			uart_putc((char)c);
-			uart_putc('\n');
-		}
-	}
+	uart_putc((char)uart_getc());
+	/* add a new line just to look better */
+	uart_putc('\n');
 }
diff --git a/code/os/07-hwtimer/uart.c b/code/os/07-hwtimer/uart.c
@@ -125,25 +125,17 @@ void uart_puts(char *s)
 
 int uart_getc(void)
 {
-	if (uart_read_reg(LSR) & LSR_RX_READY){
-		return uart_read_reg(RHR);
-	} else {
-		return -1;
-	}
+	while (0 == (uart_read_reg(LSR) & LSR_RX_READY))
+		;
+	return uart_read_reg(RHR);
 }
 
 /*
  * handle a uart interrupt, raised because input has arrived, called from trap.c.
  */
 void uart_isr(void)
 {
-	while (1) {
-		int c = uart_getc();
-		if (c == -1) {
-			break;
-		} else {
-			uart_putc((char)c);
-			uart_putc('\n');
-		}
-	}
+	uart_putc((char)uart_getc());
+	/* add a new line just to look better */
+	uart_putc('\n');
 }
diff --git a/code/os/08-preemptive/uart.c b/code/os/08-preemptive/uart.c
@@ -125,25 +125,17 @@ void uart_puts(char *s)
 
 int uart_getc(void)
 {
-	if (uart_read_reg(LSR) & LSR_RX_READY){
-		return uart_read_reg(RHR);
-	} else {
-		return -1;
-	}
+	while (0 == (uart_read_reg(LSR) & LSR_RX_READY))
+		;
+	return uart_read_reg(RHR);
 }
 
 /*
  * handle a uart interrupt, raised because input has arrived, called from trap.c.
  */
 void uart_isr(void)
 {
-	while (1) {
-		int c = uart_getc();
-		if (c == -1) {
-			break;
-		} else {
-			uart_putc((char)c);
-			uart_putc('\n');
-		}
-	}
+	uart_putc((char)uart_getc());
+	/* add a new line just to look better */
+	uart_putc('\n');
 }
diff --git a/code/os/09-lock/uart.c b/code/os/09-lock/uart.c
@@ -125,25 +125,17 @@ void uart_puts(char *s)
 
 int uart_getc(void)
 {
-	if (uart_read_reg(LSR) & LSR_RX_READY){
-		return uart_read_reg(RHR);
-	} else {
-		return -1;
-	}
+	while (0 == (uart_read_reg(LSR) & LSR_RX_READY))
+		;
+	return uart_read_reg(RHR);
 }
 
 /*
  * handle a uart interrupt, raised because input has arrived, called from trap.c.
  */
 void uart_isr(void)
 {
-	while (1) {
-		int c = uart_getc();
-		if (c == -1) {
-			break;
-		} else {
-			uart_putc((char)c);
-			uart_putc('\n');
-		}
-	}
+	uart_putc((char)uart_getc());
+	/* add a new line just to look better */
+	uart_putc('\n');
 }
diff --git a/code/os/10-swtimer/uart.c b/code/os/10-swtimer/uart.c
@@ -125,25 +125,17 @@ void uart_puts(char *s)
 
 int uart_getc(void)
 {
-	if (uart_read_reg(LSR) & LSR_RX_READY){
-		return uart_read_reg(RHR);
-	} else {
-		return -1;
-	}
+	while (0 == (uart_read_reg(LSR) & LSR_RX_READY))
+		;
+	return uart_read_reg(RHR);
 }
 
 /*
  * handle a uart interrupt, raised because input has arrived, called from trap.c.
  */
 void uart_isr(void)
 {
-	while (1) {
-		int c = uart_getc();
-		if (c == -1) {
-			break;
-		} else {
-			uart_putc((char)c);
-			uart_putc('\n');
-		}
-	}
+	uart_putc((char)uart_getc());
+	/* add a new line just to look better */
+	uart_putc('\n');
 }
diff --git a/code/os/11-syscall/uart.c b/code/os/11-syscall/uart.c
@@ -125,25 +125,17 @@ void uart_puts(char *s)
 
 int uart_getc(void)
 {
-	if (uart_read_reg(LSR) & LSR_RX_READY){
-		return uart_read_reg(RHR);
-	} else {
-		return -1;
-	}
+	while (0 == (uart_read_reg(LSR) & LSR_RX_READY))
+		;
+	return uart_read_reg(RHR);
 }
 
 /*
  * handle a uart interrupt, raised because input has arrived, called from trap.c.
  */
 void uart_isr(void)
 {
-	while (1) {
-		int c = uart_getc();
-		if (c == -1) {
-			break;
-		} else {
-			uart_putc((char)c);
-			uart_putc('\n');
-		}
-	}
+	uart_putc((char)uart_getc());
+	/* add a new line just to look better */
+	uart_putc('\n');
 }