The imx_transmit_buffer function should return if TX DMA has already
been started and not just skip over the buffer PIO write loop. (Which
did fix the initial problem, but could have unintentional side-effects)
Tested on an i.MX6Q board with half-duplex RS-485 and with RS-232.
Cc: Clemens Gruber <clemens.gruber@xxxxxxxxxxxx>
Cc: Uwe-Kleine König <u.kleine-koenig@xxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Fabio Estevam <fabio.estevam@xxxxxxx>
Fixes: 514ab34dbad6 ("serial: imx: Prevent TX buffer PIO write when a DMA has been started")
Signed-off-by: Ian Jamison <ian.dev@xxxxxxxxxx>
---
This is an alternative to Clemens Gruber's patch with subject
("serial: imx: Improve PIO prevention if TX DMA has been started")
drivers/tty/serial/imx.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 97b6923513a1..89bcf6ac9d46 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -458,7 +458,10 @@ static inline void imx_transmit_buffer(struct imx_port *sport)
}
}
- while (!uart_circ_empty(xmit) && !sport->dma_is_txing &&
+ if (sport->dma_is_txing)
+ return;
+
+ while (!uart_circ_empty(xmit) &&
!(readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)) {
/* send xmit->buf[xmit->tail]
* out the port here */
--
2.14.1
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