The current driver does not implement the flush_buffer hook for
uart_ops. When we enable the DMA for the driver, and test it with Bluetooth,
we may meet the following bug for TX:
[1] User application may call the flush operation at any time.
The uart_flush_buffer() calls the uart_circ_clear() to set
the xmit->head and xmit->tail with 0.
[2] The TX DMA callback can be called at any time too.
The dma_tx_call() will update the xmit->tail.
If [2] occurs just after the [1], we will get the wrong xmit->tail.
This patch implements the flush_buffer hook to fix this issue.
Signed-off-by: Huang Shijie <b32955@xxxxxxxxxxxxx>
---
drivers/tty/serial/imx.c | 11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index c07d9bb..708ba89 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1303,6 +1303,16 @@ static void imx_shutdown(struct uart_port *port)
clk_disable_unprepare(sport->clk_ipg);
}
+static void imx_flush_buffer(struct uart_port *port)
+{
+ struct imx_port *sport = (struct imx_port *)port;
+
+ if (sport->dma_is_enabled) {
+ sport->tx_bytes = 0;
+ dmaengine_terminate_all(sport->dma_chan_tx);
+ }
+}
+
static void
imx_set_termios(struct uart_port *port, struct ktermios *termios,
struct ktermios *old)
@@ -1623,6 +1633,7 @@ static struct uart_ops imx_pops = {
.break_ctl = imx_break_ctl,
.startup = imx_startup,
.shutdown = imx_shutdown,
+ .flush_buffer = imx_flush_buffer,
.set_termios = imx_set_termios,
.type = imx_type,
.release_port = imx_release_port,
--
1.7.2.rc3
--
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