UART: Remove X-on/X-off flow control

This doesn't appear to be used anymore, and the EC3PO replacement
console doesn't support this yet.  This also makes changing the UART
driver API more difficult, so let's remove it.

Signed-off-by: Anton Staaf <robotboy@chromium.org>

BRANCH=None
BUG=None
TEST=make buildall -j

Change-Id: Ia6d9cf4c89e34683f38169dbec612a417c6ba630
Reviewed-on: https://chromium-review.googlesource.com/340842
Commit-Ready: Anton Staaf <robotboy@chromium.org>
Tested-by: Anton Staaf <robotboy@chromium.org>
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>

1 files changed, 10 insertions, 50 deletions

diff --git a/common/uart_buffering.c b/common/uart_buffering.c
index c750a1ef6e..b81c8cf065 100644
--- a/common/uart_buffering.c
+++ b/common/uart_buffering.c
@@ -27,9 +27,6 @@
 #define TX_BUF_DIFF(i, j) (((i) - (j)) & (CONFIG_UART_TX_BUF_SIZE - 1))
 #define RX_BUF_DIFF(i, j) (((i) - (j)) & (CONFIG_UART_RX_BUF_SIZE - 1))
 
-/* ASCII control character; for example, CTRL('C') = ^C */
-#define CTRL(c) ((c) - '@')
-
 /*
  * Interval between rechecking the receive DMA head pointer, after a character
  * of input has been detected by the normal tick task.  There will be
@@ -49,7 +46,6 @@ static int tx_snapshot_head;
 static int tx_snapshot_tail;
 static int tx_last_snapshot_head;
 static int tx_next_snapshot_head;
-static int uart_suspended;
 
 /**
  * Put a single character into the transmit buffer.
@@ -115,9 +111,6 @@ void uart_process_output(void)
 	 */
 	int head = tx_buf_head;
 
-	if (uart_suspended)
-		return;
-
 	/* If DMA is still busy, nothing to do. */
 	if (!uart_tx_dma_ready())
 		return;
@@ -149,9 +142,6 @@ void uart_process_output(void)
 
 void uart_process_output(void)
 {
-	if (uart_suspended)
-		return;
-
 	/* Copy output from buffer until TX fifo full or output buffer empty */
 	while (uart_tx_ready() && (tx_buf_head != tx_buf_tail)) {
 		uart_write_char(tx_buf[tx_buf_tail]);
@@ -166,6 +156,9 @@ void uart_process_output(void)
 #endif /* !CONFIG_UART_TX_DMA */
 
 #ifdef CONFIG_UART_RX_DMA
+#ifdef CONFIG_UART_INPUT_FILTER  /* TODO(crosbug.com/p/36745): */
+#error "Filtering the UART input with DMA enabled is NOT SUPPORTED!"
+#endif
 
 void uart_process_input(void);
 DECLARE_DEFERRED(uart_process_input);
@@ -175,30 +168,9 @@ void uart_process_input(void)
 	static int fast_rechecks;
 	int cur_head = rx_buf_head;
 
-	int i;
-
 	/* Update receive buffer head from current DMA receive pointer */
 	rx_buf_head = uart_rx_dma_head();
 
-	/* Handle software flow control characters */
-	for (i = cur_head; i != rx_buf_head; i = RX_BUF_NEXT(i)) {
-		int c = rx_buf[i];
-
-#ifdef CONFIG_UART_INPUT_FILTER  /* TODO(crosbug.com/p/36745): */
-#error "Filtering the UART input with DMA enabled is NOT SUPPORTED!"
-#endif
-
-		if (c == CTRL('S')) {
-			/* Software flow control - XOFF */
-			uart_suspended = 1;
-			uart_tx_stop();
-		} else if (c == CTRL('Q')) {
-			/* Software flow control - XON */
-			uart_suspended = 0;
-			uart_tx_start();
-		}
-	}
-
 	if (rx_buf_head != cur_head) {
 		console_has_input();
 		fast_rechecks = CONFIG_UART_RX_DMA_RECHECKS;
@@ -234,15 +206,7 @@ void uart_process_input(void)
 			continue;
 #endif
 
-		if (c == CTRL('S')) {
-			/* Software flow control - XOFF */
-			uart_suspended = 1;
-			uart_tx_stop();
-		} else if (c == CTRL('Q')) {
-			/* Software flow control - XON */
-			uart_suspended = 0;
-			uart_tx_start();
-		} else if (rx_buf_next != rx_buf_tail) {
+		if (rx_buf_next != rx_buf_tail) {
 			/* Buffer all other input */
 			rx_buf[rx_buf_head] = c;
 			rx_buf_head = rx_buf_next;
@@ -260,8 +224,7 @@ int uart_putc(int c)
 {
 	int rv = __tx_char(NULL, c);
 
-	if (!uart_suspended)
-		uart_tx_start();
+	uart_tx_start();
 
 	return rv ? EC_ERROR_OVERFLOW : EC_SUCCESS;
 }
@@ -274,8 +237,7 @@ int uart_puts(const char *outstr)
 			break;
 	}
 
-	if (!uart_suspended)
-		uart_tx_start();
+	uart_tx_start();
 
 	/* Successful if we consumed all output */
 	return *outstr ? EC_ERROR_OVERFLOW : EC_SUCCESS;
@@ -285,8 +247,7 @@ int uart_vprintf(const char *format, va_list args)
 {
 	int rv = vfnprintf(__tx_char, NULL, format, args);
 
-	if (!uart_suspended)
-		uart_tx_start();
+	uart_tx_start();
 
 	return rv;
 }
@@ -304,8 +265,8 @@ int uart_printf(const char *format, ...)
 
 void uart_flush_output(void)
 {
-	/* If UART not initialized or is suspended, ignore flush request. */
-	if (!uart_init_done() || uart_suspended)
+	/* If UART not initialized ignore flush request. */
+	if (!uart_init_done())
 		return;
 
 	/* Loop until buffer is empty */
@@ -342,8 +303,7 @@ int uart_getc(void)
 		int c = rx_buf[rx_buf_tail];
 		rx_buf_tail = RX_BUF_NEXT(rx_buf_tail);
 
-		if (c != CTRL('Q') && c != CTRL('S'))
-			return c;
+		return c;
 	}
 
 	/* If we're still here, no input */