Simplify uart_tx_start()

All calls to it did

    if (uart_tx_stopped())
        uart_tx_start();

And that was the only use of uart_tx_stopped().  Merge the functions.

BUG=chrome-os-partner:20485
BRANCH=none
TEST=EC debug console still prints output and accepts commands.
     Ctrl+Q pauses output and Ctrl+S resumes it.

Change-Id: I113c64f5fdfc6b02b63034a74b1a3c6c6a76c351
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/169329
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

4 files changed, 15 insertions, 23 deletions

diff --git a/chip/lm4/uart.c b/chip/lm4/uart.c
index c7d320928c..ff24718a07 100644
--- a/chip/lm4/uart.c
+++ b/chip/lm4/uart.c
@@ -25,6 +25,10 @@ int uart_init_done(void)
 
 void uart_tx_start(void)
 {
+	/* If interrupt is already enabled, nothing to do */
+	if (LM4_UART_IM(0) & 0x20)
+		return;
+
 	/*
 	 * Re-enable the transmit interrupt, then forcibly trigger the
 	 * interrupt.  This works around a hardware problem with the
@@ -40,11 +44,6 @@ void uart_tx_stop(void)
 	LM4_UART_IM(0) &= ~0x20;
 }
 
-int uart_tx_stopped(void)
-{
-	return !(LM4_UART_IM(0) & 0x20);
-}
-
 void uart_tx_flush(void)
 {
 	/* Wait for transmit FIFO empty */
diff --git a/chip/stm32/uart.c b/chip/stm32/uart.c
index c848f0b20c..3d510c16f1 100644
--- a/chip/stm32/uart.c
+++ b/chip/stm32/uart.c
@@ -41,6 +41,10 @@ int uart_init_done(void)
 
 void uart_tx_start(void)
 {
+	/* If interrupt is already enabled, nothing to do */
+	if (STM32_USART_CR1(UARTN) & UART_TX_INT_ENABLE)
+		return;
+
 	disable_sleep(SLEEP_MASK_UART);
 	should_stop = 0;
 	STM32_USART_CR1(UARTN) |= UART_TX_INT_ENABLE;
@@ -54,11 +58,6 @@ void uart_tx_stop(void)
 	enable_sleep(SLEEP_MASK_UART);
 }
 
-int uart_tx_stopped(void)
-{
-	return !(STM32_USART_CR1(UARTN) & UART_TX_INT_ENABLE);
-}
-
 void uart_tx_flush(void)
 {
 	while (!(STM32_USART_SR(UARTN) & STM32_USART_SR_TXE))
diff --git a/common/uart_buffering.c b/common/uart_buffering.c
index 784e117503..560e783c41 100644
--- a/common/uart_buffering.c
+++ b/common/uart_buffering.c
@@ -146,8 +146,7 @@ void uart_process_input(void)
 		} else if (c == CTRL('S')) {
 			/* Software flow control - XON */
 			uart_suspended = 0;
-			if (uart_tx_stopped())
-				uart_tx_start();
+			uart_tx_start();
 		} else if (rx_buf_next != rx_buf_tail) {
 			/* Buffer all other input */
 			rx_buf[rx_buf_head] = c;
@@ -165,7 +164,7 @@ int uart_putc(int c)
 {
 	int rv = __tx_char(NULL, c);
 
-	if (!uart_suspended && uart_tx_stopped())
+	if (!uart_suspended)
 		uart_tx_start();
 
 	return rv ? EC_ERROR_OVERFLOW : EC_SUCCESS;
@@ -179,7 +178,7 @@ int uart_puts(const char *outstr)
 			break;
 	}
 
-	if (!uart_suspended && uart_tx_stopped())
+	if (!uart_suspended)
 		uart_tx_start();
 
 	/* Successful if we consumed all output */
@@ -190,7 +189,7 @@ int uart_vprintf(const char *format, va_list args)
 {
 	int rv = vfnprintf(__tx_char, NULL, format, args);
 
-	if (!uart_suspended && uart_tx_stopped())
+	if (!uart_suspended)
 		uart_tx_start();
 
 	return rv;
@@ -222,7 +221,7 @@ void uart_flush_output(void)
 			 * we're in now.
 			 */
 			uart_process_output();
-		} else if (uart_tx_stopped()) {
+		} else {
 			/*
 			 * It's possible we switched from a previous context
 			 * which was doing a printf() or puts() but hadn't
diff --git a/include/uart.h b/include/uart.h
index bada502c8b..9e182002e1 100644
--- a/include/uart.h
+++ b/include/uart.h
@@ -149,8 +149,8 @@ void uart_enable_interrupt(void);
 /**
  * Re-enable the UART transmit interrupt.
  *
- * This also forces triggering an interrupt if the hardware doesn't
- * automatically trigger it when the transmit buffer was filled beforehand.
+ * This also forces triggering a UART interrupt, if the transmit interrupt was
+ * disabled.
  */
 void uart_tx_start(void);
 
@@ -160,11 +160,6 @@ void uart_tx_start(void);
 void uart_tx_stop(void);
 
 /**
- * Return non-zero if the UART transmit interrupt is disabled.
- */
-int uart_tx_stopped(void);
-
-/**
  * Helper for processing UART input.
  *
  * Reads the input FIFO until empty.  Intended to be called from the driver