This patch adds Software flow control support in DMA mode.
Signed-off-by: Jiada Wang <jiada_w...@mentor.com>
---
drivers/tty/serial/imx.c | 30 ++++++++++++++++++++++++++++--
1 file changed, 28 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 301cf8c..642e88e 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -464,9 +464,11 @@ static void imx_enable_ms(struct uart_port *port)
mod_timer(&sport->timer, jiffies);
}
+static void imx_dma_tx(struct imx_port *sport);
static inline void imx_transmit_buffer(struct imx_port *sport)
{
struct circ_buf *xmit = &sport->port.state->xmit;
+ unsigned long temp;
if (sport->port.x_char) {
/* Send next char */
@@ -481,6 +483,22 @@ static inline void imx_transmit_buffer(struct imx_port
*sport)
return;
}
+ if (sport->dma_is_enabled) {
+ /*
+ * We've just sent a X-char Ensure the TX DMA is enabled
+ * and the TX IRQ is disabled.
+ **/
+ temp = readl(sport->port.membase + UCR1);
+ temp &= ~UCR1_TXMPTYEN;
+ if (sport->dma_is_txing) {
+ temp |= UCR1_TDMAEN;
+ writel(temp, sport->port.membase + UCR1);
+ } else {
+ writel(temp, sport->port.membase + UCR1);
+ imx_dma_tx(sport);
+ }
+ }
+
while (!uart_circ_empty(xmit) &&
!(readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)) {
/* send xmit->buf[xmit->tail]
@@ -497,7 +515,6 @@ static inline void imx_transmit_buffer(struct imx_port
*sport)
imx_stop_tx(&sport->port);
}
-static void imx_dma_tx(struct imx_port *sport);
static void dma_tx_callback(void *data)
{
struct imx_port *sport = data;
@@ -630,7 +647,16 @@ static void imx_start_tx(struct uart_port *port)
}
if (sport->dma_is_enabled) {
- /* FIXME: port->x_char must be transmitted if != 0 */
+ if (sport->port.x_char) {
+ /* We have X-char to send, so enable TX IRQ and
+ * disable TX DMA to let TX interrupt to send X-char */
+ temp = readl(sport->port.membase + UCR1);
+ temp &= ~UCR1_TDMAEN;
+ temp |= UCR1_TXMPTYEN;
+ writel(temp, sport->port.membase + UCR1);
+ return;
+ }
+
if (!uart_circ_empty(&port->state->xmit) &&
!uart_tx_stopped(port))
imx_dma_tx(sport);
--
1.9.3
--
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