Currently, if one switches to rs232 mode, writes something to the
device, and then switches to rs485 mode, the imx_port's ->tx_state is
left as SEND. This then prevents a subsequent write in rs485 mode from
properly asserting the rts pin (i.e. enabling the transceiver),
because imx_uart_start_rx() does not enter the "if (sport->tx_state ==
OFF)" branch. Hence nothing is actually transmitted.
The problem is that in rs232 mode, ->tx_state never gets set to OFF,
due to
usr2 = imx_uart_readl(sport, USR2);
if (!(usr2 & USR2_TXDC)) {
/* The shifter is still busy, so retry once TC triggers */
return;
}
in imx_uart_stop_tx(), and TC never triggers because the Transmit
Complete interrupt is not enabled for rs232.
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@xxxxxxxxx>
---
I'm not sure this is the best fix.
At first I considered doing something much more targeted, but
definitely also more hacky: In imx_uart_rs485_config(), if switching
on rs485 mode, simply add "sport->tx_state = OFF;".
If someone has a better suggestion, I'm all ears.
drivers/tty/serial/imx.c | 24 +++++++++---------------
1 file changed, 9 insertions(+), 15 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 7341d060f85c..ffee157e13cd 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -708,25 +708,19 @@ static void imx_uart_start_tx(struct uart_port *port)
|| sport->tx_state == WAIT_AFTER_RTS) {
hrtimer_try_to_cancel(&sport->trigger_stop_tx);
-
- /*
- * Enable transmitter and shifter empty irq only if DMA
- * is off. In the DMA case this is done in the
- * tx-callback.
- */
- if (!sport->dma_is_enabled) {
- u32 ucr4 = imx_uart_readl(sport, UCR4);
- ucr4 |= UCR4_TCEN;
- imx_uart_writel(sport, ucr4, UCR4);
- }
-
- sport->tx_state = SEND;
}
- } else {
- sport->tx_state = SEND;
}
+ sport->tx_state = SEND;
+
+ /*
+ * Enable transmitter and shifter empty irq only if DMA is
+ * off. In the DMA case this is done in the tx-callback.
+ */
if (!sport->dma_is_enabled) {
+ u32 ucr4 = imx_uart_readl(sport, UCR4);
+ ucr4 |= UCR4_TCEN;
+ imx_uart_writel(sport, ucr4, UCR4);
ucr1 = imx_uart_readl(sport, UCR1);
imx_uart_writel(sport, ucr1 | UCR1_TRDYEN, UCR1);
}
--
2.40.1.1.g1c60b9335d
