Revert "serial: imx: always wake up the processes in the TX callback"
This reverts commit 2ad28e3efee21a5bbf940c83d1f0395b76bd3efb.
Instead of always wake up write_wait process in TX callback,
TX callback should call imx_dma_tx() again, and let imx_dma_tx
transfer the remaining data in circle buffer.
The issue with commit 2ad28e3 is, in case there is remaining
data in circle buffer, but no process is waiting on write_wait
queue, then as no following uart_write() will be called after
uart_write_wakeup(), thus cause data loss.
Moreover according to Documentation/serial/driver, uart_write_wakeup()
should be called in case the transmit buffer have dropped below
a threshold.
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 1c4f367..73158d9 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -516,7 +516,8 @@
spin_unlock_irqrestore(&sport->port.lock, flags);
- uart_write_wakeup(&sport->port);
+ if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+ uart_write_wakeup(&sport->port);
if (waitqueue_active(&sport->dma_wait)) {
wake_up(&sport->dma_wait);